Nrca Roof Manual

The NRCA Green Roof Systems Manual 2007 Edition

The NRCA Green Roof Systems Manual— 2007 Edition

National Roofing Contractors Association 10255 W. Higgins Road, Suite 600 Rosemont, IL 60018-5607 (847) 299-9070 Fax: (847) 299-1183 Web site: www.nrca.net E-mail: [email protected] Published by the National Roofing Contractors Association 10255 W. Higgins Road, Suite 600, Rosemont, IL 60018-5607 ©2007 by the National Roofing Contractors Association All rights reserved Published 2007 Printed in the United States of America No part of this publication may be reproduced or distributed in any form or by any means or stored in a database or retrieval system without prior written permission of the publisher.

The NRCA Green Roof Systems Manual—2007 Edition

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Important Legal Notice for Users of The NRCA Green Roof Systems Manual—2007 Edition Purpose of the Manual The NRCA Green Roof Systems Manual—2007 Edition (Manual) is published by the National Roofing Contractors Association (NRCA) for educational and informational purposes only. NRCA is not undertaking to render specific professional advice. Readers must rely solely on their own judgment or consult a technically competent roofing professional to determine what procedure, whether included in the Manual or not, is appropriate for their purpose. NRCA does not “approve” or “endorse” any specific products, methods, practices or sources of information. The Manual should not be referenced in any way that implies such approval or endorsement.

Disclaimers The information and data contained in the Manual have been obtained from sources believed to be reliable. However, the various codes, regulations, standards and practices referenced in the Manual are subject to change, and the Manual is current only as of its original publication date. Make sure to consult appropriate sources for the most up-to-date versions of all codes, regulations and standards. Further, it should not be assumed that (i) all acceptable or applicable sources of information, procedures and techniques are contained in the Manual, or (ii) additional measures may not be required under certain circumstances or conditions. NRCA makes no guarantee, representation or warranty, express or implied, at law or in equity, and NRCA expressly disclaims any and all such guarantees, representations or warranties whatsoever as to the validity, accuracy or sufficiency of the information set forth in the Manual and assumes no responsibility or liability in connection therewith. Although NRCA recommends the use of the Manual by private industry and others, it is intended to be voluntary and nonbinding, and NRCA assumes no liability or responsibility in connection with the use or misuse of the Manual or information included therein, or in connection with any modifications to or adaptations of the Manual by a user, purchaser or other party, and expressly disclaims any such liability or responsibility. By using the information contained in the Manual, the user expressly assumes all risk of loss, harm or injury resulting from the use or misuse of such information. Additionally, the information presented in the Manual is complex, may not be appropriate in all instances, and requires verification and use by technically competent roofing professionals. Modification to all or parts of the information included in the Manual by the user may affect the results, accuracy, reliability or other aspects of the information. By using the Manual, the user acknowledges and accepts the foregoing limitation of liability and disclaimers, and agrees that NRCA is not responsible for injuries, claims, losses or damages to the user or third parties arising directly or indirectly out of the user’s use of the Manual and/or the information contained therein.

Amendments NRCA may, from time to time, amend and/or update the Manual. Such updates and amendments may create significant differences among successive editions of the Manual. The Manual is current only as of the original publication date indicated thereon.

Copyright NRCA owns all copyrights in the Manual. The contents of the Manual may not, in whole or in part, be reproduced, copied or disseminated, entered into or stored in a computer database or retrieval system, or otherwise used without the prior written consent of NRCA except that users may reproduce a limited number of pages, figures or construction details solely for purposes of responding to proposals, preparing shop drawings and similar noncommercial, limited uses.

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The NRCA Green Roof Systems Manual—2007 Edition

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Foreword The NRCA Green Roof Systems Manual—2007 Edition is written to provide technical information concerning the design and installation of quality green roof systems.

Charles Bechtel Harold J. Becker Co. Inc. Dayton, Ohio

The information contained in this manual represents the consensus of knowledgeable, practicing waterproofing and green roof system contractors throughout the U.S. In developing and publishing this manual, the National Roofing Contractors Association (NRCA) is presenting time-tested and proven bestpractice guidelines that are applicable throughout the U.S. for roofing and waterproofing buildings and other structures. These guidelines may be more conservative than practices employed by some designers, manufacturers and installers. NRCA recognizes some designs and applications may vary according to climatic conditions and some geographical areas may employ area practices that are sound and time-proven. NRCA does not mean to imply by any statement or exclusion in this manual that such practices are unsatisfactory or inappropriate.

Thomas R. Dessent Dessent Roofing Co. Chicago

The science and art of roofing and waterproofing buildings and other structures continue to experience change spurred largely by technological innovations and new product developments. Ongoing and new research is also expanding the industry’s knowledge of roof and waterproofing systems and their design and installation. NRCA is committed to maintaining The NRCA Green Roof Systems Manual—2007 Edition as an up-todate, authoritative technical reference concerning the design and installation of quality roof and waterproofing systems. Future updated editions of this manual are planned as new significant information about roof and waterproofing systems and their design and installation becomes available. Users of this manual who are seeking clarification of its guidelines or wish to submit recommendations for revisions or additions to future editions of this manual should contact: Technical Services Section National Roofing Contractors Association 10255 W. Higgins Road, Suite 600 Rosemont, IL 60018 (847) 299-9070 Fax: (847) 299-1183 E-mail: [email protected]

Acknowledgments NRCA gratefully acknowledges its task force and committee members who contributed their time, effort and expertise in the development of this manual. NRCA’s Waterproofing Task Force was primarily responsible for researching and analyzing topics and developing the text, figures and construction details contained in this manual. The members of this task force at the time the manual was developed and published were: Frank E. Lawson Jr., task force chairman The Lawson Roofing Co. Inc. San Francisco

Don Guthrie Wayne’s Roofing Inc. Sumner, Wash. Robert W. Therrien Jr. The Melanson Co. Inc. Keene, N.H. James R. Kirby, AIA, NRCA staff liaison National Roofing Contractors Association Rosemont, Ill. Also, members of NRCA’s Manual Update Committee, Technical Operations Committee and Executive Committee provided review comments for the manual and input and guidance to the Waterproofing Task Force. In addition, NRCA acknowledges the efforts and expertise of its staff involved in the development and publication of the manual, including staff from its Technical Services Section and the editing and print production staff of the Communications and Membership Development Section.

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Contents General Green Roof Project Considerations Green Roof System Guidelines

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Green Roof System Construction Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47 Glossary

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The NRCA Green Roof Systems Manual— 2007 Edition General Green Roof Project Considerations

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Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 2. Notes to Owners and Designers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 2.1 Proper Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 2.2 Quality Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 2.3 Quality Workmanship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 3. Pre-bid Conference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 4. Pre-job Conference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 5. Material Storage and Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 6. Temporary Green Roof Waterproofing System . . . . . . . . . . . . . . . . . . . . . . . . .15 7. Weather Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 7.1 Cold Temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 7.2 Hot Temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 7.3 Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 7.4 Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 8. Deck and Structural Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . .16 9. Surface Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 10. Slope and Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 11. Expansion Joints and Control Joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 12. Curbs and Penetrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 13. Flashings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 13.1 Membrane Base Flashings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 13.2 Sheet-metal Counterflashings and Terminations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 14. Quality Assurance and Water Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 15. Overburden . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 16. Post-water-test Considerations

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17. Warranties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 18. Building Owner Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 19. Pre-job Conference Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

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The NRCA Green Roof Systems Manual—2007 Edition

1. Introduction

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• Slope and drainage • Green roof waterproofing membrane

The General Green Roof Project Considerations section of this manual has been written to provide an overview of general information concerning the design and installation of quality green roof systems. The information contained in this document is intended to complement The NRCA Roofing Manual series and should be used as a guideline to prepare proper specifications. Consult The NRCA Roofing Manual: Membrane Roof Systems— 2007 and The NRCA Roofing and Waterproofing Manual, Fifth Edition for more data and specification information.

• Green roof system type (e.g., intensive [deep]), including overburden • Accessibility and building configuration • Building movement • Type and amount of insulation, protection and drainage needed • Need for ventilation during installation

This information represents the consensus of professional green roof system contractors throughout the U.S. A green roof system contractor is a professional waterproofing or roof system contractor familiar with the installation of green roof systems. A green roof system is a roof area of plantings/landscaping installed above a waterproofed substrate. Some design criteria and application techniques may vary according to climatic conditions, and each geographical area may employ specific “area practices” that are sound and time-proven for that area. NRCA does not intend to imply by any statement or exclusion that proven area practices are unsatisfactory.

• Compatibility with adjacent building and/or system components

The NRCA Green Roof Systems Manual—2007 Edition defines green roof system, green roof assembly and waterproofing as follows:

• Penetrations

• Green roof system: a roof area of plantings/landscaping installed above a waterproofed substrate at any building level that is separated from the ground beneath it by a man-made structure. A green roof system consists of a waterproofing system and its associated components—such as protection course, root barrier, drainage layer, thermal insulation and aeration layer—and an overburden of growth medium and plantings. • Green roof assembly: a substrate and a green roof system. • Waterproofing: treatment of a surface or structure to prevent the passage of water under hydrostatic conditions. Green roof system technology and building construction continues to evolve. New, ongoing research is expanding the industry’s knowledge of green roof assemblies and their design and installation. Readers are encouraged to contact NRCA or NRCA members in their geographical area for specific advice concerning area practices and current technical information. NRCA recommends a green roof system be designed only after a number of criteria have been carefully considered, including:

• Construction sequencing • Worker safety • Potential building additions • Odors generated by certain system application methods • Snow loads, water-retention loads • Construction traffic

• Landscape maintenance These criteria play important roles in the ultimate success or failure of a green roof assembly and should be considered by a designer to determine the appropriate components of a green roof assembly, applicable products and specifications, and construction details to be used. In addition, a designer should be certain green roof material manufacturers’ requirements are taken into account, as well as requirements of applicable insurance, building code enforcement and/or other regulatory agencies. It is recommended designers communicate with the manufacturer and consult material manufacturers’ specifications during the design of a green roof assembly.

2. Notes to Owners and Designers Achieving a green roof system that will perform its functions satisfactorily for an anticipated service life requires proper design, quality materials and quality workmanship.

2.1 Proper Design

• Climate and geographical location • A building’s intended use and design life expectancy • Exterior and interior temperature, humidity and use conditions • Code requirements • LEED™ considerations

Knowledgeable selection of compatible building materials, quality green roof system materials and systems that will withstand the conditions of the area where a building is located is vital to a quality green roof assembly design. Properly prepared specifications with accurate drawings and details are essential. Specific requirements regarding a new green roof assembly’s components and installation should be carefully detailed by a designer.

• Type and condition of substrate • Structural system

A designer is responsible for proper specifications and drawings. Green roof system contractors and material manufacturers should be consulted for input during the design phase.

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The NRCA Green Roof Systems Manual—2007 Edition

2.2 Quality Materials

documents and distributed to all parties in a timely manner following the meeting and well in advance of the bid deadline.

Material selection should be based on the time-proven quality of a green roof assembly and its compatibility and appropriateness to the substrate rather than solely on economic considerations or length and scope of a warranty.

In summary, a pre-bid conference, if conducted properly, can result in more accurate bidding and fewer change orders during construction, as well as a more thorough understanding of the project.

2.3 Quality Workmanship

4. Pre-job Conference

NRCA suggests designers work with qualified professional green roof system contractors and consult them during the design phase and before specifications or contract documents are prepared. The work should be performed by skilled, trained workers familiar with the specified product.

3. Pre-bid Conference For green roof system projects for which drawings and specifications have been prepared and two or more green roof system contractors are asked to submit sealed bids to perform specified work, NRCA recommends a pre-bid conference be conducted. A pre-bid conference can serve the following purposes: • Introduce all the parties involved in the project, such as the owner’s representative, designer, landscape contractor and contractor’s key personnel • Provide a forum for a thorough review of the project documents and requirements and the owner’s special needs • Establish the conditions under which temporary waterproofing and/or traffic paths will be used and who will pay for them • Provide an opportunity to identify and resolve any questions, discrepancies, contradictions or errors in written specifications and drawings • Provide an opportunity to discuss best practices, as well as limitations for job-site setup, work hours, staging, storing materials, and removal of materials and debris

Once a project has been awarded, NRCA recommends a pre-job conference be held for green roof system projects. This conference should be attended by the owner, architect/engineer or designer, general contractor, site contractor, green roof system contractor, consultant, inspector or quality-assurance supervisor, deck contractor, landscaping contractor, mechanical contractor, electrical contractor and any others whose work may interface with or affect the waterproofing project. The conference should be scheduled well in advance of any deck completion and before ordering materials and beginning work. If a manufacturer’s guarantee or warranty is specified, representatives from the waterproofing material manufacturer(s) should be present. A written record should be made of the proceedings from this meeting and should become a part of the job record. If a green roof system contractor or waterproofing materials manufacturer discovers problems during inspection of a deck, a second preinstallation inspection attended by the affected parties should be held to verify corrective measures have been taken. A designer’s specifications, plans, and all green roof system and flashing details should be reviewed at the pre-job conference. Any discrepancies between the designer’s contract documents and manufacturer’s specifications should be discussed and resolved. In the event that certain discrepancies arise, the manufacturer’s representative should be consulted to assist in resolving the issue. Any known building code or architectural directives that conflict with these requirements should be resolved. NRCA recommends the directives listed below be followed to ensure a successful pre-job conference:

• Identify and resolve any misconceptions in the scope of work • Review approved submittals for the green roof system. • Identify the quality-control and inspection process Before scheduling a pre-bid conference, a designer or building owner’s representative should prepare an agenda for the meeting and distribute it to all invited parties. If the identity of interested bidders cannot be determined before the pre-bid conference, such as in public bid projects, the agenda should be posted and made available to potential attendees before the conference. A pre-bid conference should be attended by all responsible parties, including the owner’s representative, the designer, estimators and key personnel of the bidding contractors and any subcontractors. The prebid meeting should be scheduled to allow adequate time for bid preparation between the pre-bid meeting and the date on which sealed bids are to be submitted. Ideally, the project documents, including the drawings and specifications, should be distributed to all the bidders before the date of the pre-bid conference to allow each bidder the opportunity to review the documents. A written record or meeting minutes of the conference should be maintained by a designer along with any changes (addenda) to the contract

• Establish trade-related job schedules and appropriate trade coordination and sequencing, including appropriate curing times; the schedule should provide for timely installation of any penetrations, attachments, equipment, overburden and/or protection to avoid or limit traffic on the green roof waterproofing membrane. • Establish construction schedules and work methods that will prevent damage to the green roof system. These may include provisions for installation of a temporary green roof waterproofing system or temporary green roof waterproofing surface protection devices, such as plywood. Installation of traffic paths or walkways helps protect a finished green roof waterproofing membrane and system from foot traffic and mechanized construction equipment. • Establish guidelines for inspection and repair of the deck, including identifying the parties who are responsible for inspection and repair.

The NRCA Green Roof Systems Manual—2007 Edition

• Coordinate all appropriate walls, curbs, drains and other penetrations before installation of the green roof system. • Establish those areas on the job site that will be designated for access, staging, work, storage and disposal areas. • Establish suitable weather conditions and working temperature criteria to which all parties should agree. • Establish provisions for on-site surveillance after green roof waterproofing membrane application is completed to ensure the finished green roof waterproofing membrane is not damaged by other trades, and if damage does occur, proper repairs are performed in a timely manner.

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with water-resistant coverings that have been properly secured. Coverings that are “breathable,” such as waterresistant tarpaulins, are preferred. • Roll materials should be stored on end to prevent rolls from becoming deformed or damaged. Single-ply sheet materials may be stored as shipped with rolls lying horizontally or as recommended by the manufacturer. When storing green roof system materials on a deck surface, caution should be taken not to overload the deck or structural assembly. • Lids should be secured on cans of stored material. • Water-based materials should be protected from freezing.

• Establish safety regulations and safety requirements, including considerations for safety of workers.

• Solvents, adhesives, foam components and sealants should be stored at proper temperatures.

• Establish quality-assurance requirements and procedures, including the level of authority to be granted to qualityassurance personnel to direct changes in the work.

• Insulation materials should be stored and handled with care. When insulation is required to be dry at the point of installation, it is imperative insulation materials be protected from weather and moisture absorption. Some insulation materials are extremely light and must be weighted in storage to prevent wind damage, and some materials may need to be protected from UV radiation.

• Establish water-testing requirements and procedures, and designate a party responsible for signing off after successfully water testing the completed green roof waterproofing membrane and/or green roof system. • Establish a timeline for proper installation of overburden.

6. Temporary Green Roof

• Establish the need for appropriate green roof waterproofing membrane personnel to be on-site when overburden is placed on the green roof waterproofing membrane in case of damage.

Waterproofing System

• Establish a quality-control and inspection process, and establish who is responsible for it. • Establish a water source for irrigation. At the conclusion of the pre-job conference, the party requesting any proposed changes to the project conditions or green roof system should: • Give written notice of the desired changes to all parties • Secure written agreement to the changes from the project designer, owner and all other parties affected by the change Additionally, the owner or designer should provide written meeting minutes to all parties with action items noted. A pre-job conference checklist is provided on page 21.

5. Material Storage and Handling NRCA recommends the following for the storage and handling of materials: • All green roof system materials that are susceptible to retaining moisture or may be damaged by moisture should be stored in a dry location and protected from freezing. • All green roof system materials that are susceptible to ultraviolet (UV) damage should be covered or stored in a location that protects them from UV damage. • When moisture-sensitive materials are stored outside, they should be placed on pallets or platforms that are raised off the ground. Materials sensitive to moisture should be covered

Frequently, building construction sequencing leads to pressure for the installation of green roof system materials during unsuitable weather conditions or ahead of the construction schedule. This can be an issue for many types of green roof system projects but is most likely to be an issue for green roof system projects above habitable spaces or for those that can be used as work platforms or staging areas for other trades. As an effective means of addressing the problems caused by construction scheduling, a temporary waterproofing system installation may be necessary. A temporary waterproofing system facilitates the application of the specified green roof system during more suitable weather but allows other trades to complete their work before the permanent green roof system is installed. Thus, other trades may stay on schedule, completing their work under the protection of the temporary waterproofing system, and other trade traffic is limited from potentially damaging the finished green roof system. If a temporary waterproofing system is to be employed, NRCA recommends the specifications clearly state a temporary waterproofing system will be required; the type and specification of temporary waterproofing system to be used; and whether the temporary waterproofing system is to remain in place as part of the permanent waterproofing assembly. If it is to remain in place, the temporary waterproofing system must be compatible with the permanent green roof system.

7. Weather Considerations The performance of a green roof system depends on adhesion of a membrane to a suitable substrate; consequently, weather conditions play an important factor in the successful installation of a

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green roof system. A green roof system contractor is vitally concerned with the limitations imposed on construction activity by the weather. To satisfy construction schedules and cope with the limitations imposed by weather, a designer, general contractor and green roof system contractor should consider the following guidelines for the application of green roof waterproofing membrane materials during various weather conditions.

7.1 Cold Temperatures It is recommended that green roof system materials that have a cold-temperature sensitivity not be applied unless correct solvent-, adhesive-, heat-welding- or bitumen-application temperatures can be maintained. For bituminous green roof system work, the heating and application of hot bitumen should conform to the manufacturer’s recommendations. If proper application temperatures cannot be maintained, green roof system application should cease. Hot bitumen must not be allowed to cool substantially before placing membrane reinforcing in the bitumen. Depending on the coldweather flexibility properties of certain modified bitumen materials, pre-warming and unrolling them in cold weather should be executed per manufacturer’s instructions. Moisture must not be allowed to condense or freeze or frost allowed to form on adhesives and solvents before bonding or welding takes place. Heat welders must be maintained at proper temperatures to provide complete, permanent welds. When installing heat-fused modified bitumen membranes in cold temperatures, equipment temperature and application rate should be adjusted to achieve thorough membrane adhesion. Concrete decks can remain excessively cold, which could have an adverse effect on the placement of the membrane and/or green roof system. Care must be taken to minimize material damage from the construction process during cold weather. Additionally, solvents generally will require more time to release from cold-applied adhesives; therefore, the curing time will be longer.

7.2 Hot Temperatures

The NRCA Green Roof Systems Manual—2007 Edition

7.3 Wind Wind can affect the application of green roof materials in many ways. Hot materials may be blown about, creating safety issues. Spray-applied liquid materials, such as adhesives and coatings, can become airborne in the wind and cause damage to surrounding property or affect the quality of the application—masking or overspray protection may be required. During even low winds, handling membrane sheet materials may become difficult and dangerous. Wind may affect proper application temperatures and curing of materials. Insulation boards, sheathing and other relatively large, bulky materials may become difficult and hazardous to handle. Debris may become airborne and can contaminate laps, seams and fluid-applied membranes, and the quality of the completed membrane may be compromised as a result.

7.4 Precipitation Green roof system materials should not be installed if water, frost, snow or ice is present on an area under construction. Materials that can be adversely affected by these elements include various deck materials, membranes, flashings, sealants and coatings. NRCA recommends most materials for green roof systems should not be installed if precipitation of any kind is occurring or is imminent unless the area is adequately protected. After moisture has been present on the substrate, it is advisable to run an adhesion test to determine whether the membrane will properly adhere to the substrate.

8. Deck and Structural Design Considerations Along with other factors, a successful green roof system application depends on a structurally sound deck. To ensure the construction of a structurally sound deck, provisions for the following items should be included in a building’s structural design and in the design of a deck: • Live loads, such as snow, ice and rain

Hot temperatures and/or conditions of high humidity also present challenges to maintaining proper application conditions for bitumens, certain solvents, adhesives and membrane-welding equipment. In hot weather, bitumen will cool more slowly, which can lead to sticking, making the membrane susceptible to physical damage from the construction process, equipment and foot traffic. Hot weather combined with construction activity also can lead to damage of certain materials. Hot weather also cures or evaporates solvents and adhesives more quickly, which can impair solvent welding, bonding and long-term adhesion. Humidity levels may also impair the welding, bonding and/or adhesion of various products. Heat welders must be properly adjusted and monitored so as not to scorch, burn or overheat materials. Concrete decks can retain an excessive amount of heat, which could have an adverse effect on the placement of the membrane and/or green roof system.

• Construction loads, such as moving installation equipment, workers and materials; some construction loads, such as roller dollies used to transport single-ply materials, can exceed 600 pounds in quite small areas • Dead loads, such as mechanical equipment, duct work, piping, and conduit such as fire sprinkler and electrical lines • Dead loads, such as a waterproofing system, soil overburden, concrete toppings, pavers and water that is retained • Deck strength (gauge, density, type and thickness) • Expected deflection • Drainage • Placement of expansion joints • Placement and structural support of curb and penetration members and details

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should specify a minimum 1⁄8:12 (0.6-degree) slope or greater and should make provisions in the design for complete positive drainage. To achieve the necessary slope throughout the entire surface area, a designer should consider the following:

• Attachment or securement provisions for a deck • Suitability for adhesion/attachment of a green roof waterproofing membrane • Suitability for water test loads

• Structural framing for the deck

A structurally sound deck should remain rigid so as not to deflect excessively under live loads. It should be understood that a green roof system contractor can only inspect the surface of a deck to receive the green roof waterproofing membrane materials and cannot assume responsibility for the deck’s slope, structural integrity, method of attachment, or any other conditions beyond his or her control or professional expertise.

• Deck type and its characteristics • Overburden material • Type of membrane specified • Penetration locations • Varying deck deflections • Building and deck layout

9. Surface Inspection

• Flashing termination heights Before applying green roof waterproofing membrane materials, it is recommended that a green roof system contractor, with the appropriate parties, visually inspect the substrate surface to verify it is clean, dry, smooth and acceptable for green roof waterproofing membrane and green roof system installation. A deck should be brush- or broom-clean, reasonably smooth, free of voids or depressions, and adequately attached. This inspection should be attended by the green roof system contractor; material manufacturer; and all the appropriate parties, such as the general contractor, deck contractor, architect/engineer or designer, and owner’s representative. All visible defects in the deck should be noted, and corrections should be made before beginning green roof system work. It is recommended that the contractor who is responsible for defects or damage to the deck be responsible for the repairs. NRCA recommends project specifications clearly define this responsibility.

10. Slope and Drainage NRCA recommends all green roof systems over habitable spaces be designed and built to provide positive drainage. For green roof systems over habitable spaces, NRCA recommends that a drainage layer be installed to facilitate the movement of water. Because every green roof system project has its own set of drainage criteria, the designer is responsible for including proper drainage provisions in the green roof system design. For green roof systems over habitable spaces, a designer

Certain decks, such as precast concrete decks or long-span prestressed concrete decks, may incorporate camber in anticipation of future loading conditions. The camber must be considered in the design of the slope and drainage system. Depending on the structural design of a deck or slab system and placement of drains, the camber may assist or restrict drainage. See Figure 1. This example illustrates that the computations for slope should be determined by the deflections expected in each particular slab/deck. NRCA recommends a designer consult the local building code of jurisdiction regarding the required slope, primary drainage and secondary (overflow) drainage for each project. Building codes dictate the number of drains, size of drain pipes and plumbing accessories, and the need for secondary drainage systems. Design information for drainage is found in the plumbing section of the applicable building code. Primary drains and overflows are typically installed at the same level as the green roof waterproofing membrane’s surface. For all green roof systems, it is recommended a protection course be installed above the green roof waterproofing membrane and under any overburden. In some green roof systems, the root barrier may also act as a protection course. For green roof systems, the drainage course is needed to promote the movement of water under insulation, reservoir layer, etc. See the construction details section of this manual for specific green roof system details.

EXAMPLE SPAN OF 50' DRAIN AT LOCATION OF MAXIMUM CAMBER MAY NOT EFFECTIVELY DRAIN THE WATERPROOFING UNDER MINIMUM LOADING CONDITIONS DRAIN LOCATED HERE AIDS DRAINAGE

LEVEL LINE CAMBER POINT OF DECK SUPPORT

POINT OF DECK SUPPORT

Figure 1: Example of deck camber where a drain located at midspan may not provide drainage

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11. Expansion Joints and Control Joints Expansion joints and control joints are used to minimize the effects of stresses and movements of a building’s components and prevent these stresses from splitting, buckling/ridging or damaging a green roof system. Expansion joints in a green roof assembly should be placed in the same location as the building’s structural expansion joints. Each of a building’s components has varying coefficients of expansion, and each is subjected to varying temperature changes and resultant thermal movement. It is the designer’s responsibility to allow for building movement and placement of expansion joints. In the design and placement of green roof system expansion and control joints, it is recommended a designer consider: • Thermal movement characteristics of a building • Structural supports and deck

The NRCA Green Roof Systems Manual—2007 Edition

a green roof waterproofing membrane and/or green roof system. All openings for penetrations should be cut through the deck and the void around the penetration filled with compatible material before installation of a green roof waterproofing membrane. Vibrations from surface-mounted mechanical equipment should be isolated from a green roof waterproofing membrane and flashings. The installation of drainage piping is encouraged to direct equipment discharge water directly to drains. Heavy loads, such as large mechanical units, should not be wheeled or rolled over a completed green roof waterproofing membrane because they may cause damage to it. Protection boards should be installed if work is required over a completed green roof waterproofing membrane before installation of the system components and overburden. After the work is completed, the temporary protection should be removed and any damage repaired and water tested. See the construction details section of this manual for specific green roof system details.

• Green roof waterproofing membrane • Climatic conditions

13. Flashings

• Proper detailing

The most vulnerable part of a green roof system for water entry is the point at which horizontal and vertical surfaces intersect, such as parapet walls and penetrations. Designers should carefully design all flashing details.

• Drainage areas/paths Where expansion joints are used, the waterproofing system should slope away from expansion joints so water does not accumulate at the base flashing of an expansion joint. See the construction details section of this manual for specific green roof system details.

12. Curbs and Penetrations NRCA recommends curbs and penetrations be flashed into the green roof waterproofing membrane. The designer should properly detail penetrations for drains, piping, conduit, mechanical units, equipment supports, and other projections or penetrations. See the Introduction to Details section of this manual for additional information regarding penetrations and clearance. A maximum amount of space should be provided between pipes, walls and curbs to facilitate proper installation of green roof system materials. NRCA recommends a minimum 12 inches of clearance between pipes, a minimum 12 inches of clearance between pipes and curbs or walls, and a minimum 12 inches of clearance between curbs and curbs or walls. Green roof systems have different installation methods that may require different spacings, and certain project conditions may not allow these recommended clearances; however, adequate space (i.e., clearance) is required for proper installation of the required flashings at penetrations. NRCA recommends penetrations through a green roof system not be located so they restrict the flow of water. Pipe clusters are not recommended because of the difficulty to properly flash them into a green roof waterproofing membrane. All curbs, wood blocking, penetrations, drains and drain leaders should be firmly anchored and in place before installation of

Flashings and membranes are subject to differential horizontal-to-vertical movement and can separate from their substrate, tear and become a source for water entry into the green roof system and/or building interior. This can cause wrinkling and buckling, delamination and loss of adhesion. NRCA recommends designers develop flashing details that can accommodate movement at horizontal-to-vertical conditions at walls and decks. This condition may occur where walls and decks are not attached to each other or fixed-in-place. There are two types of flashings for green roof systems: membrane base flashings and sheet-metal counterflashings.

13.1 Membrane Base Flashings Membrane base flashings are generally composed of strips of compatible membrane materials used to flash horizontal-tovertical junctions and/or transitions. NRCA recommends the height of a base flashing be a minimum of 8 inches above the surface of the membrane and 4 inches above the surface of the growth medium. Membrane base flashings should be adhered to the substrate to prevent displacement and/or slippage. Depending on the type of green roof system, termination of the system may vary. Some systems require securing or fastening by termination bars or other appropriate mechanical fastening devices approved by the membrane manufacturer. Membrane base flashings also should be properly sealed along the top edge. When phasing is required, other parties, such as the general contractor, should be responsible for protection of the exposed green roof waterproofing membrane or leading edge before completion of the flashing system.

The NRCA Green Roof Systems Manual—2007 Edition

The installation of fillets at membrane base flashings to accommodate horizontal-to-vertical plane change is consistent with good green roof system practice when using bituminous green roof waterproofing membranes. Most thermoset and thermoplastic green roof systems are capable of accommodating 90-degree angle changes and do not require the use of fillets.

13.2 Sheet-metal Counterflashings and Terminations When green roof system base flashings are subject to UV exposure, sheet-metal counterflashings should be installed to cover the top edge and overlap the exposed portion of membrane base flashings. In lieu of sheet-metal counterflashings, some other means of protecting the membrane flashing from UV exposure and physical damage is needed. However, some green roof systems do not require counterflashing to protect them from UV exposure. Sheet-metal counterflashings should be installed into or on the wall above the base flashing. NRCA suggests the design of counterflashings consist of separate reglet and counterflashing pieces, allowing installation of the sheet-metal counterflashing after the membrane base flashing is complete. Projects where single-piece counterflashings have been installed will require removal and replacement of the metal flashing during future maintenance and rewaterproofing operations.

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green roof system to the precast wall units. Cast-in raggles or reglets frequently used for this purpose are difficult to align. When they are not horizontally aligned, they hinder the proper installation of sheet-metal reglets and counterflashing components. For this reason, the use of cast-in raggles or reglets is not recommended. Also, where counterflashings span vertical panelto-panel joints, the interfaces of counterflashings and panels with sealants are difficult to waterproof. In these situations, consideration should be given to camber, and the independent thermal movement of the walls, green roof waterproofing membrane and flashings. Because metals have thermal expansion and contraction characteristics that differ from most green roof waterproofing membranes, it is advisable to isolate metal flashings from the green roof waterproofing membrane and flashing when possible.

14. Quality Assurance and Water Tests Continuous visual inspection during green roof waterproofing membrane and green roof system application provides a complete and meaningful means of examining workmanship practices. If part-time inspections are performed, the inspections should occur at the beginning and end of significant phases and when another construction trade’s work may affect the performance of the green roof system. The quality-assurance representative’s responsibilities should be clearly defined to ensure complete understanding of expectations of materials to be installed, installation methods and definition of deficiencies with appropriately defined corrective actions. The representative should, in a timely manner, provide the green roof system contractor with copies of all reports prepared for the owner and should orally inform the contractor’s field personnel of locations of items requiring corrective action at the time of observation. Quality assurance by the owner should continue after completion of the green roof waterproofing membrane until all overburden work is completed. NRCA strongly recommends horizontal green roof waterproofing membranes used as part of a green roof system be watertested to prove their integrity prior to permitting subsequent construction. It is recommended the water test be witnessed and the results confirmed in writing in case a problem arises after job completion. Before installation of overburden, a water test is conducted to evaluate whether a green roof membrane is leak-free under hydrostatic (e.g., standing water) and/or nonhydrostatic conditions (e.g., flowing water). Prior to performing a water test, all appropriate parties and trades should be notified when the water test will occur. A water test is conducted in one of two ways:

Figure 2: Surface-mounted reglet with removable counterflashing

When precast walls are used, a designer should carefully consider the flashing provisions required to properly interface the

• A standing-water test is conducted by temporarily plugging or otherwise closing any deck drains and erecting temporary dams where required to retain water on the surface of the green roof waterproofing membrane then flooding the surface to a maximum depth of 2 inches at the high point and retaining the water for a minimum of 24 hours or as required by the manufacturer. Installation and removal of any temporary dams should not damage the membrane.

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• A flowing-water test is conducted by applying continuously flowing water over the green roof waterproofing membrane’s surface without closing drains or erecting dams for a minimum of 24 hours or as required by the manufacturer. Selecting the correct water test depends on the structural capacity of the deck/substrate and the slope of the deck/green roof system. However, job-site conditions may dictate the methodology of each project’s water test. Decks without significant slope can be water-tested using a flood test or a flowingwater test. Decks with significant slope (e.g., a steep-slope green roof system) can be water-tested using a flowing-water test. Determining the structural capacity of the deck is the responsibility of the designer. Care must be taken so the weight of water retained does not exceed the load-carrying capacity of the structural deck and the height of the water does not exceed the height of the lowest flashing. The water should be allowed to remain on the green roof waterproofing membrane for a minimum of 24 hours for the flood test or for the flowing-water test or as required by the manufacturer, after which the areas beneath the membrane should be inspected for leaks. If leaks are detected, the test should be stopped, repairs made to the membrane and the area retested for a minimum of 24 hours. The protection course should be installed over the tested area after successfully completing the water test unless a protection course is an integral part of the green roof waterproofing membrane. The water test documents the performance of the green roof waterproofing membrane prior to placement of system components and overburden. After the waterproofing test has been successfully completed, cover the membrane with a protection course, root barrier, moisture-resistant insulation and/or drainage course. Avoid all unnecessary traffic on the completed system prior to installation of the remaining components. If surfaces are exposed to the sun or if the green roof waterproofing membrane is being installed during extremely hot weather, installation of the protection course should occur within 24 hours. This information and a sample water-test verification form are located in the Appendixes in the Green Roof System Guidelines section of this manual. Other methods, such as electric field vector mapping, are available to help determine the location of leaks, if they should occur, either during a water test or after the green roof system is completed. This low-voltage test uses water as a conductive medium and a wire-loop configuration to create an electrical potential difference between a nonconductive membrane surface and a conductive structural deck or substrate, which is grounded. By applying water on the membrane surface, an electric field is created, and breaches in the membrane create vectors (ground fault connections). These vectors enable technicians to locate green roof waterproofing membrane defects. This method can be configured to locate leaks within a green roof system.

15. Overburden Consideration should be given to the selection of the overburden and the components above a green roof waterproofing membrane.

The NRCA Green Roof Systems Manual—2007 Edition

A protection course, root barrier, drainage layer, moisture-resistant insulation, aeration layer, moisture-retention layer, reservoir layer and growth medium are installed on top of a green roof waterproofing membrane. The selection of the overburden is a significant part of an overall green roof system. The top of the overburden should be 4 inches below the top of the flashing terminations. The components above a green roof waterproofing membrane should all be compatible. Accessory items, such as electrical conduits, irrigation lines, piping, etc., should not be attached to a green roof system.

16. Post-water-test Considerations After a waterproofing system has been installed, the green roof system contractor and the general contractor should advise the appropriate parties of the need to provide surveillance and protection of the green roof waterproofing membrane until the protection course, system components and overburden are installed. Accessory items, such as electrical conduits, irrigation lines, piping, etc., should not be attached to a green roof waterproofing membrane. Prolonged exposure of the green roof waterproofing membrane to UV radiation also should be avoided to prevent damage. Damage to a green roof system caused by other trades is a major source of subsequent green roof system problems. Construction traffic, staging, other trades’ work, debris and contaminants should be kept off a finished green roof waterproofing membrane. Damage can be difficult to discover, and leaks or points of water entry into the green roof system can remain undetected for an extended period of time, which can lead to further problems, such as structural deterioration. Where construction damage is anticipated, the use of a temporary waterproofing system should be considered before a project begins.

17. Warranties The length of a waterproofing system warranty should not be a primary criterion in the selection of a green roof waterproofing membrane or green roof system because the warranty does not necessarily provide assurance of satisfactory green roof system performance. The selection of a green roof system for a particular project should be based on the product’s qualities and suitability for the prospective construction project. A long-term warranty may be of little value to a consumer if the green roof system does not perform satisfactorily and the owner is plagued by leaks. Conversely, if a green roof system is well-designed, wellconstructed and well-manufactured, the expense of purchasing a warranty may not be necessary. Warranty documents often contain restrictive provisions that significantly limit the warrantor’s liability and consumer’s remedies in the event that problems develop. The warranty document may also contain other restrictions and limitations, such as a preclusion against assignment or transfer of the warranty, exclusion of damages resulting from a defective green roof system and inclusion of monetary limitations. It is NRCA’s position that the removal of growth medium, equipment, etc., that are not strictly part of the green roof system is the responsibility of others. A green roof system contractor and green roof material

The NRCA Green Roof Systems Manual—2007 Edition

supplier are not responsible for removing any overburden of any kind installed by others over the green roof waterproofing membrane, including equipment, machinery, etc. It is recommended the respective manufacturers be consulted for warranty clarification and responsibilities.

18. Building Owner Recommendations Building owners should file all job records, drawings, specifications and the water-test verification form for future reference. They should record maintenance procedures as they occur. The following should be included in an owner’s maintenance program: • Remove debris from the green roof system because debris may be swept toward drains and may clog them. Check drain inspection ports for soil and debris accumulation. • Notify the green roof system contractor immediately upon discovery of a green roof system leak. • Note conditions resulting in leakage. • Note whether the leak starts immediately after rain begins, stops shortly after rain stops or continues to leak until the green roof system is dry. All associated facts enable the diagnosis and repair of green roof system problems to proceed more rapidly. • Do not allow the installation of new penetrations through a completed green roof system without consulting with the green roof system contractor and membrane manufacturer (if the green roof system is under a manufacturer’s warranty) about the methods and details for these installations. • Make the landscape maintenance workers aware they should not damage exposed materials, especially the waterproofing layer and flashings. Specific safety precautions may need to be followed by trades working in a roof environment. • Make sure the installing green roof system contractor flashes and seals future penetrations when they are are added.

19. Pre-Job Conference Checklist NRCA recommends the directives listed below be followed to ensure a successful pre-job conference: I Review approved submittals for the green roof system.

I Establish trade-related job schedules and appropriate trade coordination and sequencing, including appropriate curing times; the schedule should provide for timely installation of any penetrations, attachments, equipment, overburden and/or protection to avoid or limit traffic on the green roof waterproofing membrane.

I Establish construction schedules and work methods that will prevent damage to a green roof system. These may include provisions for installation of a temporary green roof waterproofing system or temporary green roof waterproofing surface protection devices, such as plywood. Installation of

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traffic paths or walkways helps protect a finished green roof waterproofing membrane and system from foot traffic and mechanized construction equipment. I Establish guidelines for inspection and repair of the deck, including identifying the parties who are responsible for inspection and repair. I Coordinate all appropriate walls, curbs, drains and other penetrations before installation of the green roof system. I Establish those areas on the job site that will be designated as access, staging, work, storage and disposal areas. I Establish suitable weather conditions and working temperature criteria to which all parties should agree. I Establish provisions for on-site surveillance after green roof waterproofing membrane application is completed to ensure the finished green roof waterproofing membrane is not damaged by other trades, and if damage does occur, proper repairs are performed in a timely manner. I Establish safety regulations and safety requirements, including considerations for safety of workers. I Establish quality-assurance requirements and procedures, including the level of authority to be granted to qualityassurance personnel to direct changes in the work. I Establish water-testing requirements and procedures, and designate a party responsible for signing off after successfully water testing the completed green roof waterproofing membrane and/or green roof system. I Establish a timeline for proper installation of overburden.

I Establish the need for appropriate green roof waterproofing membrane personnel to be on-site when overburden is placed on the green roof waterproofing membrane in case of damage. I Establish a quality-control and inspection process and who is responsible for it. I Establish a water source for irrigation. At the conclusion of the pre-job conference, the party requesting any proposed changes to the project conditions or green roof system should: I Give written notice of the desired changes to all parties

I Secure written agreement to the changes from the project designer, owner and all other parties affected by the change Additionally, the owner or designer should provide written meeting minutes to all parties with actions noted.

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The NRCA Green Roof Systems Manual— 2007 Edition Green Roof System Guidelines

The NRCA Green Roof Systems Manual—2007 Edition

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Contents 1. Introduction

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

2. Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 2.1 Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 2.2 Semi-intensive (Moderate Depth) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 2.3 Intensive (Deep) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 3. Green Roof System Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 3.1 Performance Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 3.2 Environmental Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 3.3 System Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 4. Decks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 4.1 Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 4.2 Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 4.3 Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 4.4 Deck Deflection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 5. Membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 5.1 Hot-fluid-applied Polymer-modified Asphalt Membrane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 5.1.1 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 5.2 APP- and SBS-polymer-modified Bitumen Sheet Membrane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 5.2.1 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36 5.3 EPDM Membrane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37 5.3.1 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37 5.4 Polyvinyl Chloride (PVC) Membrane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37 5.4.1 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 5.5 One- and Two-component Fluid-applied Elastomeric Membranes . . . . . . . . . . . . . . . . . . . . . . . . . . .38 5.5.1 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 6. System Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39 6.1 Protection Course . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 6.2 Root Barrier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 6.3 Drainage Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 6.4 Moisture-resistant Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 6.5 Aeration Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 6.6 Moisture-retention Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 6.7 Reservoir Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 6.8 Filter Fabric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 6.9 Engineered Soil-based Growth Medium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 7. Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 7.1 Inspection Boxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

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8.

9. 10. 11. 12. 13. 14.

The NRCA Green Roof Systems Manual—2007 Edition

7.2 Irrigation and Electrical Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 7.3 Overburden Dividers and Terminations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 7.4 Drain Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 7.5 Metal Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 7.6 Area Dividers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 8.1 System Assemblies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 8.2 Building Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 8.3 Quality Assurance and Water Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 Low-slope vs. Steep-slope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 Care and Maintenance by Green Roof System Contractor . . . . . . . . . . . . . . . . .43 Care and Maintenance by Landscaping Contractor . . . . . . . . . . . . . . . . . . . . . .44 Reroofing Guidelines for Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . .44 Converting a Conventional Roof to a Green Roof System . . . . . . . . . . . . . . . . . .44 Appendixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44 14.1 Guidelines and Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44 14.2 Water-test Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 14.3 Water-test Verification Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46

The NRCA Green Roof Systems Manual—2007 Edition

1. Introduction The Green Roof System Guidelines section of this manual is written to provide in-depth technical information concerning the design and installation of quality green roof systems. Green roof system practices vary considerably in different parts of the U.S. because of the variety of conditions that exist and the various materials that are available for use. Many times, green roof systems are essentially customized, meaning they are designed for specific substrates and structures and applied on job sites. Adherence to the practices outlined in this manual is an option of each contracting firm. Area practices and the timeproven methods employed by individual firms are frequently given priority over these recommended general procedures.

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The recommendations contained in the Green Roof System Construction Details section of this manual should not be construed as the only methods for designing and installing green roof systems. Some design criteria and application techniques may vary according to climatic conditions, and some geographical areas employ “area practices” that are sound and timeproven. NRCA does not mean to imply by any statement or exclusion that time-tested and proven area practices are unsatisfactory or inappropriate. Users of this manual are encouraged to contact NRCA members in their geographical areas for specific advice concerning area practices and current technical information. The Green Roof System Guidelines section of this manual is composed of the following sections:

Green roof systems can be divided into three primary categories: extensive (shallow), semi-intensive (moderate depth) and intensive (deep), which are defined as follows:

• Introduction—This section contains general definitions and information applicable to all green roof systems and defines the green roof waterproofing membrane types NRCA recommends for green roof systems.

• Extensive (shallow) green roof system: green roof system with an engineered soil-based growth medium approximately 2 inches to 6 inches deep

• Green Roof Systems—This section contains general information and definitions of the three common types of green roof systems.

• Semi-intensive (moderate depth) green roof system: green roof system with an engineered soil-based growth medium approximately 6 inches to 10 inches deep

• Green Roof System Characteristics—This section contains information about the performance attributes, environmental benefits and components of green roof systems.

• Intensive (deep) green roof system: green roof system with an engineered soil-based growth medium greater than 10 inches deep

• Decks—This section contains information on the common types of decks used with green roof systems.

The green roof system details provided in this manual provide design and installation information for: • Hot-fluid-applied polymer-modified asphalt membrane • APP- and SBS-polymer-modified bitumen sheet membrane • EPDM membrane • Polyvinyl chloride (PVC) membrane • One- and two-component fluid-applied elastomeric membrane The information contained in this manual is intended primarily to address new construction and replacement green roof system situations. Because of the wide variety of green roof system products, this manual cannot address all the different methods and practices for designing and installing all the products available to designers, contractors and building owners. In this manual, the National Roofing Contractors Association (NRCA) attempts to present the consensus of knowledgeable, practicing green roof system and waterproofing contractors throughout the U.S. as to the practices and procedures for good roofing and waterproofing. Where this manual provides specific suggestions or recommendations, it should be noted these may be a more conservative approach than may be commonly provided by individual product manufacturers, green roof system designers or green roof system contractors. The green roof system design and application procedures included in this manual are recognized to be sound and time-proven and apply throughout the U.S.

• Membranes—This section contains material and installation information about green roof waterproofing membranes used in green roof systems. • System Components—This section contains general information about system components that are integral to the waterproofing, drainage, moisture retention and growth media used in green roof systems. • Accessories—This section contains general information about system accessories such as inspection boxes, irrigation lines, overburden dividers and metal components used in green roof systems. • Additional information about design considerations, low- and steep-slope systems, care and maintenance, reroofing, standards and water tests also is provided. Construction details applicable to green roof systems are provided in the Green Roof Systems Construction Details section of this manual. NRCA suggests the Green Roof System Guidelines section of this manual be used in the design of green roof systems only after careful review of the General Green Roof Project Considerations section of this manual and a number of criteria have been carefully considered, including: • Climate and geographic location • A building’s intended use and design life expectancy • Exterior and interior temperature, humidity and use conditions • Code requirements

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• LEED™ considerations • Type and condition of substrate • Structural system • Slope and drainage • Green roof waterproofing membrane • Green roof system type (e.g., intensive [deep]), including overburden • Accessibility and building configuration • Building movement • Type and amount of insulation, protection and drainage needed • Need for ventilation during installation • Compatibility with adjacent building and/or system components • Construction sequencing • Worker safety • Potential building additions • Odors generated by certain system application methods • Snow loads, water retention loads • Construction traffic • Penetrations • Landscape maintenance These criteria play an important role in the ultimate success or failure of every green roof system assembly and must be considered by a designer to determine the appropriate components of a green roof assembly, applicable products and specifications, and construction details to be used. In addition, a designer should be certain green roof system product manufacturer’s requirements are taken into account, as well as requirements of applicable insurance, building code enforcement and/or other regulatory agencies. It is recommended that material manufacturers’ written specifications be cosulted during the design of a green roof system.

2. Green Roof Systems The term “green roofing” is generally accepted as the description of a roof system with a surface of landscaped plantings. NRCA defines a green roof system as a roof area of planting/landscaping installed above a waterproofed substrate at any building level that is separated from the ground beneath it by a man-made structure. A green roof system consists of a waterproofing system and its associated components—such as protection course, root barrier, drainage layer, thermal insulation and aeration layer—and an overburden of growth medium and plantings. Green roofing should be differentiated from the constructionindustry term “green building.” Green buildings are designed, constructed and operated to boost environmental, economic,

The NRCA Green Roof Systems Manual—2007 Edition

health and productivity performance over that of conventional buildings, according to the U.S. Green Building Council. Green building encompasses the full building envelope and the building’s immediate surroundings. A green roof system by association is a component of green building, but more specifically, it is a planted waterproofing system installed over a habitable space. NRCA considers a green roof system the combination of a waterproofing system, its associated green roof components, and an overburden of growth medium and plantings. The term “green roof system” does not include plaza deck systems (i.e., hard-scape areas), individual planters or a water-protection system that can be identified as a roof or waterproofing system. Green roof systems are also referred to as garden roofs, eco-roofs, vegetated roofs and numerous other terms. Regulatory agencies may describe green roof systems relative to design and composition predicated on energy and environmental incentives. NRCA’s intent is to provide specific guidelines and recommendations for decks, green roof waterproofing membranes and the intermediate system components of green roof systems. A green roof system is a combination of roof system, waterproofing, and landscaping concepts and components. A basic principle of a green roof system is that it consists of a green roof waterproofing membrane as the means to prevent moisture from entering a habitable building or space. The following are differences between a green roof system and a conventional waterproofing or roof system: • A green roof system needs to be compatible with the plants and vegetation and must resist contamination from fertilizers and other chemicals and materials used in conjunction with the vegetation. • A green roof system is more susceptible to mechanical damage and abuse, especially during installation. • A green roof system must be protected from the tools used to maintain the overburden/vegetation. • A waterproofing roof membrane for a green roof system is not readily accessible after the overburden is installed. Designers should be more conservative with their design, membrane selection and detailing. • A green roof system is exposed to landscaping, cultivation, vegetation work and human error. The landscape portion of a green roof system will require periodic maintenance; maintenance workers should be made aware that they should not damage exposed materials, especially the waterproofing layer and flashings. Specific safety precautions may need to be followed by maintenance and landscaping trades working in a roof environment. • A green roof system is protected from ultraviolet (UV) exposure and impact but still is exposed to thermal and environmental changes. NRCA recommends a green roof system incorporate a directto-deck fully adhered waterproofing system. NRCA recognizes a green roof system can include a loose-laid or partially adhered

The NRCA Green Roof Systems Manual—2007 Edition

(e.g., gridded attachment) membrane. However, NRCA does not recommend the use of these types of attachment methods for green roof systems due to the potential for leak travel. “Leak travel” is the ability of water to migrate horizontally from the initial point of water entry, which makes it more difficult to locate a leak source/point of entry. Once an unadhered membrane is compromised/breached, water has the potential to get under the membrane, whereas a breach in a fully adhered membrane may not allow moisture beneath the membrane. This reduces the potential for a leak to occur. A green roof system may incorporate an insulation layer. If an insulation layer is included, the recommended location is above the green roof waterproofing membrane. The insulation layer should be high-density, have a high compressive strength and be moisture-resistant. The waterproofing system must be able to withstand a moist environment for a prolonged period of time. The substrate (i.e., structural deck) for the green roof waterproofing membrane should be sloped to provide positive drainage. NRCA does not recommend tapered insulation under the membrane. NRCA recognizes there are green roof systems that incorporate rigid board insulation and/or rigid tapered insulation beneath a membrane. However, NRCA does not recommend the use of insulation under a green roof waterproofing membrane for green roof systems due the potential for leak travel and damage to the insulation layer. This type of green roof system is fully adhered to the insulation or may be loose-laid and ballasted by the overburden. If a green roof waterproofing membrane for a green roof system is fully adhered above the insulation layer, NRCA recommends a layer of rigid board, such as a water-resistant gypsum board or cementitious board, be fully adhered to mechanically attached or fully adhered insulation prior to installation of the membrane. If insulation is installed under a green roof waterproofing membrane, it should be fully adhered or mechanically attached, not loose-laid. If a structural deck is not sloped, insulation installed under a green roof waterproofing membrane should include rigid tapered insulation to provide positive drainage. Because NRCA is concerned that insulation shrinkage may occur, the insulation board joints should be taped to prevent gaps from occurring. Additionally, insulation installed under a green roof waterproofing membrane must have adequate compressive strength to properly support the membrane and overburden. Traditional roof insulations do not have the compressive strength that is necessary to provide proper support for the membrane and overburden. The use of high-density, moistureresistant insulation with a high compressive strength is recommended regardless of whether the insulation is above or below a green roof waterproofing membrane. Green roof system types are defined by the landscaping portion of the system. There are three types of green roof systems: extensive (shallow), semi-intensive (moderate depth) and intensive (deep). The green roof waterproofing membrane component is the same in all three types; however, the other system components vary based on the plantings and landscaping placed above the waterproofing system. The selection of the plants and land-

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scaping determines which system components are needed. For example, the type of root barrier, the membrane-protection layer and the water-retaining layer vary based on the plant selection and landscaping.

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Figure 3: Extensive (shallow) green roof system

2.1 Extensive (Shallow) Green Roof Systems Extensive green roof systems use a narrower range of species limited to herbs, low-growing grasses, mosses and droughttolerant succulents such as sedum—a plant variety known for its tolerance for extreme conditions. These types of plants can potentially be sustained in a growth medium layer as shallow as 2 inches to 6 inches and can be designed for steeper slopes (slopes greater than 2:12 [9 degrees]). Saturated weights for extensive green roof systems can start at approximately 12 pounds per square foot and increase from there. Extensive green roof systems require a root barrier and a moisture-retention layer and generally do not require irrigation. A water reservoir layer may not be required. Extensive green roof systems can often be installed on existing buildings without the cost of major structural alterations. However, it is suggested that an engineering analysis of the structure supporting the roof system be performed.

The NRCA Green Roof Systems Manual—2007 Edition

The NRCA Green Roof Systems Manual—2007 Edition

Figure 4: Semi-intensive (moderate depth) green roof system

2.2 Semi-intensive (Moderate Depth) Green Roof Systems Semi-intensive green roof systems use a combination of plant species that may include small shrubs and species like grasses and herbs and are generally limited to low-slope structures of 2:12 (9 degrees) or less. Use of these plants requires a growth medium layer from 6 inches to 10 inches. Saturated weights for semi-intensive green roof systems can start at approximately 40 pounds per square foot and increase from there. Semi-intensive green roof systems have landscaping requiring more regular maintenance than an extensive system but are limited in plant selection due to shallower soil depths, such as a sod grass lawn. These systems will require a reservoir layer and may require an irrigation system.

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The NRCA Green Roof Systems Manual—2007 Edition

Figure 5: Intensive (deep) green roof system

2.3 Intensive (Deep) Green Roof Systems Intensive green roof systems use a wide variety of plant species that may include trees and shrubs and are generally limited to low-slope structures of 1⁄4:12 (1.2 degrees) or less. Use of large plants requires a deeper growth medium layer, typically 10 inches or more, which results in greater weight and a need for an increased structural load capacity of the building. Saturated weights for intensive green roof systems can start at approximately 60 pounds per square foot and increase from there. Intensive green roof systems typically require a heavy root

barrier and often require irrigation. These systems will require a reservoir layer. Additionally, an efficient drainage layer may be required due to the quantity of water from irrigation and project conditions.

The NRCA Green Roof Systems Manual—2007 Edition

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3. Green Roof System

• Reservoir layer

Characteristics

• Moisture-retention layer • Aeration layer

A green roof system can enhance certain performance attributes of an individual building. The system can also complement the environmental features of the immediate and surrounding areas.

3.1 Performance Attributes

• Moisture-resistant insulation • Drainage layer • Root barrier • Protection course

Green roof systems have a number of performance attributes. They are as follows: • Growth medium depth and vegetation may increase thermal efficiency, particularly during warm months. • Interior noise levels may be reduced because of the increased amount of sound-absorbing materials. • Membrane service life may be extended by reducing thermal shock and shielding UV exposure. • Green roof systems provide storm-water management, including water-quality benefits and flooding and erosion control. • Green roof systems can improve efficiency of roof-mounted photovoltaic panels and reduce radiation from communication towers. • Green roof systems provide aesthetic benefits to occupants and adjacent buildings. • Green roof systems may provide economic benefits in the form of rebates from planning and developmental agencies and covenants. • Green roof systems are environmentally friendly.

• Green roof waterproofing membrane system The design of the deck, green roof waterproofing membrane system, protection course, drainage layer and root barrier (if needed) is dictated by the specific overburden type selected, either extensive (shallow), semi-intensive (moderate depth) or intensive (deep). Additionally, the design of these components is based on dead and live loads, such as expected water retention (ice and snow loads), expected water drainage and the root structure of the plantings. NRCA recommends waterproofing systems be fully adhered to the substrate and be able to provide hydrostatic resistance based on the expected amount of water drainage and retention. The protection course must be capable of protecting the membrane during placement of overburden. A root barrier is required to resist root penetration. The drainage and retention layers must provide adequate flow characteristics and retention ability to support the growth of the plantings in the overburden (e.g., the engineered soil-based growth medium). Moisture-resistant insulation can be included as fill to lighten the overall weight of the system, add thermal resistance to the green roof system and maintain a proper growing and dormancy environment for plantings. It is suggested green roof systems be internally drained.

• Green roof systems can provide LEED benefits. • Green roof systems can reduce rooftop temperatures.

3.2 Environmental Features Green roof systems provide a number of environmental features. They are as follows:

4. Decks Green roof assemblies include a structural deck, a green roof waterproofing membrane and its associated green roof components, and an overburden consisting of an engineered soil-based growth medium with plantings.

• Provide a microclimate for horticultural therapy

A green roof system will require additional structural requirements based on additional dead load and live load (saturated growth medium), additional ice and snow (due to lack of heat loss), and water retention. The weight per cubic foot of saturated soil is heavier than dry soil. NRCA recommends a structural engineer be used when designing the structure under any green roof system.

• Mitigate urban heat island effects

Decks for a green roof system typically consist of:

• Improve local, particularly urban, air quality • Improve wildlife habitats and vegetation growth • Improve community green space and preserve ecological balance

3.3 System Components

• Concrete • Steel

The following is a list of common components used within a green roof system:

• Wood

• Engineered soil-based growth medium with plantings

For additional information about roof decks, refer to Chapter 1— Roof Decks in The NRCA Roofing Manual: Membrane Roof Systems—2007.

• Filter fabric layer

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4.1 Concrete Concrete substrates should be properly cured and the surface should be dry before installing waterproofing materials. The concrete surface should be finished and cured according to the waterproofing manufacturer’s recommendations. Hydration must occur in concrete substrates to the degree that the surfaces become dry enough to accommodate application of waterproofing systems. If a suitable surface cannot be obtained within a reasonable time period, direct membrane adhesion should be postponed. An adhesion test is recommended to determine appropriate membrane adhesion. Form-release agents and concrete-curing compounds must be compatible with the waterproofing materials being used or must be removed from the concrete surface by the responsible trade. Honeycombs, tie-wire holes and other voids in the concrete substrate must be cut out and filled with a nonshrinking concrete patching compound. Concrete fins or other projections should be removed to provide a smooth surface. Horizontal concrete slabs should be free from gouges, voids, depressions, ridges and concrete droppings. Concrete decks must be sloped for drainage. ASTM D5295, “Standard Guide for Preparation of Concrete Surfaces for Adhered (Bonded) Membrane Waterproofing System,” provides additional recommendations regarding the preparation of concrete deck surfaces before the installation of waterproofing. ASTM D5295 suggests tests be performed to evaluate the surface condition of concrete before installing waterproofing membranes. NRCA does not recommend the use of the surface dryness test referenced in D5295, which is D4263, “Test Method for Indicating Moisture in Concrete by the Plastic Sheet Method,” to determine whether concrete is dry enough for application of a green roof waterproofing membrane. In general terms, the test method consists of taping an 18- by 18-inch polyethylene sheet to the concrete surface and observing whether moisture collects on the underside of the polyethylene sheet. NRCA does not feel this is an appropriate test method for determining concrete deck dryness for the installation of green roof waterproofing membranes. NRCA suggests performing an adhesion test by applying a small test patch (e.g., 36- by 36inch test patch) of the green roof waterproofing membrane, allowing it to cure and then attempting to peel the membrane from the concrete substrate to determine adhesion. Performing a peel test provides for a determination of how moisture content, dust, oil, laitance and curing compounds affect adhesion. There is no standardized peel-test method, so this must be coordinated with the green roof system contractor, manufacturer and owner. Alternately, the waterproofing manufacturer should provide an appropriate test method to determine dryness of the concrete deck or an appropriate test to determine adhesion.

The NRCA Green Roof Systems Manual—2007 Edition

membrane. Overlay boards should be a minimum 5⁄8 inch thick. Fasteners used for attaching overlay boards must be corrosionresistant or resin-coated screws and plates. Overlay boards also should improve the stiffness and reduce deflection of the steel deck/overlay board composite. Steel decks must be sloped for drainage. Significant deflection will increase the possibility of ponding water and/or nonpositive drainage. Deflection needs to be accounted for when determining drainage scenarios.

4.3 Wood Wood decks should consist of heavy lumber (e.g., 3- to 4-inchthick planks) and have moisture-resistant gypsum board or cementitious board fastened to their top surfaces to serve as the green roof waterproofing membrane’s substrate. Overlay boards should be a minimum 5⁄8 inch thick. Fasteners used for attaching overlay boards must be corrosion-resistant or resin-coated screws and plates. The surface of marine-grade plywood substrates must be smooth, and holes, open joints or gaps between boards or panels should be plugged or covered. Knotholes are not acceptable for surface-applied waterproofing purposes. Joints between plywood boards should be stripped in prior to application of the green roof waterproofing membrane. Marine-grade plywood decks must be sloped for drainage. Plywood panel edges should bear on joists or blocking to reduce deflection from traffic. The thickness and deflection characteristics of wood substrates are important design considerations.

4.4 Deck Deflection A critical issue of the substrate for the waterproofing is the amount of deflection that will occur during dead and live loading. Too much deflection can be detrimental to the service life of a waterproofing system. NRCA recommends a structural engineer design the deck so that deflection of the deck is suitable to minimize the potential for ponding water.

5. Membranes NRCA recommends green roof systems incorporate a waterproofing system that is fully adhered directly to the substrate. The membrane should be able to provide hydrostatic resistance based on the expected amount of water drainage and retention. The types of membrane recommended are as follows: • Hot-fluid-applied polymer-modified asphalt membrane— fabric-reinforced, nominal 215 mils minimum thickness • APP- and SBS-polymer-modified bitumen sheet membrane— two ply minimum

4.2 Steel

• EPDM membrane—reinforced, 60 mils minimum thickness, stripped-in laps

Steel decks should be 18 gauge minimum and have moistureresistant gypsum board or cementitious board fastened to their top surfaces to serve as the green roof waterproofing membrane’s substrate. Joints between overlay boards should be stripped in prior to application of the green roof waterproofing

• Polyvinyl chloride (PVC) membrane—reinforced, 80 mils minimum thickness, stripped-in laps • One- and two-component fluid-applied elastomeric membranes—fabric-reinforced

The NRCA Green Roof Systems Manual—2007 Edition

NRCA recognizes other waterproofing membrane types may be used as part of a green roof system; however, NRCA recommends the use of only the membranes listed above for green roof systems. Regardless of the membrane type, green roof waterproofing membranes should have the following properties: low water absorption, low vapor transmission, puncture resistance, chemical resistance (e.g., fertilizer) and the ability to resist design forces through tensile strength or elongation. It is suggested that the membrane manufacturer be consulted for necessary specific chemical resistance.

5.1 Hot-fluid-applied Polymer-modified Asphalt Membrane Hot-fluid-applied polymer-modified asphalt consists of refined asphalt, synthetic rubbers and extenders. The material is typically supplied in 50-pound cakes wrapped in polyethylene film, shipped in individual cartons or containers that weigh 400 to 600 pounds. The cakes are melted in a double-jacketed oil bath or hot-air kettle and applied as a liquid that quickly cools to form a solid membrane material. NRCA recommends the membrane be fabric-reinforced with a nominal 215 mils minimum thickness. Hot-fluid-applied polymer-modified asphalt membrane waterproofing should generally not be installed when ambient temperatures are below 32 F. If application at lower temperatures is necessary due to project conditions, consult the manufacturer for specific cold-temperature application recommendations. Installation should not proceed when moisture is present. Hotfluid-applied polymer-modified asphalt membrane waterproofing cannot be left exposed to prolonged periods of sunlight and must be covered to protect it from UV light. There are few standards for hot-fluid-applied polymermodified asphalt waterproofing materials. Manufacturers generally provide specific physical property data according to standard ASTM International test methods.

5.1.1 Installation Form-release agents and concrete-curing compounds must be compatible with the waterproofing materials being used or must be removed from the concrete surface by the responsible trade. The substrate must be structurally sound. Surfaces to receive hot-fluid-applied polymer-modified asphalt membrane waterproofing must be broom-clean; adequately cured and dry; reasonably smooth; and free of dust, dirt, voids, cracks, sharp projections, oil and grease. Cracks 1⁄16 inch or wider, control joints and construction joints should be addressed separately with an additional ply of reinforced membrane prior to the application of the primary membrane system. Large cracks may need to be routed and filled with sealant prior to installation of the additional ply of reinforced membrane. Concrete surfaces should be properly cured. The elapsed time between placement of concrete and installation of the waterproofing material will be as recommended by the material manufacturer. Masonry block surfaces should be parged or filled as recommended by the manufacturer.

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Suspended slabs to be waterproofed must be vented from underneath so that moisture can be dissipated. Horizontal surfaces should be sloped for drainage. Prime the surface with primer as recommended by the manufacturer of the waterproofing materials. Reinforce inside and outside corners, cracks and construction joints with a 6-inchwide piece of reinforcing sheet embedded in hot-liquid-applied polymer-modified asphalt. Apply the hot-liquid-applied polymermodified asphalt as a continuous coating to the required thickness. Typical application consists of a nominal 90-mil-thick base coat, embedded fabric reinforcement, a nominal 125-mil-thick top coat and a protection board. Exposed vertical surfaces need additional protection when other finish materials are not used. Expansion joints and similar details should be installed according to the manufacturer’s recommendations. Use the base flashing material as recommend by the membrane manufacturer at the junction of vertical and horizontal surfaces and at penetrations. Construction details applicable to green roof systems are provided in the Green Roof System Construction Details section of this manual. NRCA strongly recommends horizontal green roof waterproofing membranes be water-tested to prove their integrity prior to permitting subsequent construction. It is recommended the water test be witnessed and the results confirmed in writing in case a problem arises after job completion. The definition and criteria for performing a water test and a suggested form for documenting a water test are included in the Appendix in the Green Roof System Guidelines section of this manual. After the waterproofing test has been successfully completed, cover the membrane with a protection course, root barrier, drainage layer and/or moisture-resistant insulation. Avoid all unnecessary traffic on the completed system prior to installation of the remaining components. If surfaces are exposed to the sun or the green roof waterproofing membrane is being installed during extremely hot weather, installation of a protection course should take place within 24 hours. For additional information, refer to ASTM D6622, “Standard Guide for Application of Fully Adhered Hot-Applied Reinforced Waterproofing Systems.”

5.2 APP- and SBS-polymer-modified Bitumen Sheet Membrane APP- and SBS-polymer-modified bitumen sheet membranes are composed of polymer-modified asphalt and one or several layers of reinforcing material. The polymer modifier extends the lowtemperature flexibility and improves the high-temperature properties of the membrane sheet. NRCA recommends APP- or SBSpolymer-modified bitumen sheet membranes for green roof systems be a minimum of two plies. Polymer-modified bitumen sheet membranes may be installed by one of three techniques depending on the composition of the

The NRCA Green Roof Systems Manual—2007 Edition

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modifier used. APP-polymer-modified sheets are either heatfused or installed in cold adhesive. Heat-fused means to be installed by heating the underside of the sheet with a propane torch or other heating device, melting the polymer-modified bitumen on the bottom side and adhering the sheet in the molten material. SBS-polymer-modified sheets are either heat-fused or installed in hot asphalt or cold adhesive. For APP- and SBS-polymer-modified sheets, NRCA recommends all seams be heatfused regardless of the membrane attachment method. Most polymer-modified bitumen sheet green roof waterproofing membranes should not be installed when the ambient temperature is below 40 F. If application at lower ambient temperatures is necessary due to project conditions, consult the membrane manufacturer for minimum temperature limitations and specific cold-temperature application recommendations. Heatfused membranes may be applied at lower temperatures. Installation should not proceed when moisture is present. APP- and SBS-polymer-modified bitumen sheet membrane waterproofing components should conform to the following recognized standards: Asphalt Primer

ASTM D41

Asphalt

ASTM D312, Type III or IV

Asphalt-impregnated Glass-fiber Mat

ASTM D2178, Type IV or VI

Asphalt-impregnated and Coated Glass-fiber Base Sheet

ASTM D4601, Type II

Styrene Butadiene Styrene- (SBS-) Modified Bituminous Sheet Materials Using a Combination of Polyester and Glass-fiber Reinforcements ASTM D6162 Styrene Butadiene Styrene- (SBS-) Modified Bituminous Sheet Materials Using Glass-fiber Reinforcements ASTM D6163 Styrene Butadiene Styrene- (SBS-) Modified Bituminous Sheet Materials Using Polyester Reinforcements ASTM D6164 Reinforced Bituminous Flashing Sheets for Roofing and Waterproofing

ASTM D6221

Atactic Polypropylene- (APP-) Modified Bituminous Sheet Materials Using Polyester Reinforcements

ASTM D6222

Atactic Polypropylene- (APP-) Modified Bituminous Sheet Using a Combination of Polyester and Glass-fiber Reinforcements

ASTM D6223

5.2.1 Installation Form-release agents and concrete-curing compounds must be compatible with the waterproofing materials being used or must be removed from the concrete surface by the responsible trade. The substrate must be structurally sound. Surfaces to receive polymer-modified bitumen waterproofing must be broom-clean; adequately cured and dry; reasonably smooth; and free of dust, dirt, voids, cracks, sharp projections, oil and grease. Cracks 1⁄16 inch or wider, control joints and construction joints should be addressed separately with an additional layer of reinforcement/ membrane prior to the application of the primary membrane system. Large cracks may need to be routed and filled with sealant prior to installation of the additional ply of reinforcement/membrane. Concrete surfaces should be properly cured. The elapsed time between placement of concrete and installation of the waterproofing material will be as recommended by the material manufacturer. Masonry block surfaces should be parged or filled as recommended by the manufacturer. Suspended slabs to be waterproofed must be vented from underneath so that moisture can be dissipated. Horizontal surfaces should be sloped for drainage. Prime the surface with primer as recommended by the manufacturer of the waterproofing materials. Reinforce inside and outside corners, cracks and construction joints with a 6-inch-wide piece of membrane sheet. Where cold adhesive is used, an appropriate amount of time must be allowed for release of solvents and curing of the adhesive prior to installation of additional green roof waterproofing membrane components and overburden. Expansion joints and similar details should be installed according to the manufacturer’s recommendations. Use the base flashing material as recommended by the membrane manufacturer at the junction of vertical and horizontal surfaces and at penetrations. Construction details applicable to green roof systems are provided in the Green Roof System Construction Details section of this manual. NRCA strongly recommends horizontal green roof waterproofing membranes be water-tested to prove their integrity prior to permitting subsequent construction. It is recommended that the results of the water test be witnessed and confirmed in writing in case a problem arises after job completion. The definition and criteria for performing a water test and a suggested form for documenting a water test are included in the Appendixes in the Green Roof System Guidelines section of this manual. After the waterproofing test has been successfully completed, cover the membrane with a protection course, root barrier, drainage layer and/or moisture-resistant insulation. Avoid all unnecessary traffic on the completed system prior to installation of the remaining components. If surfaces are exposed to the sun or if the green roof waterproofing membrane is being installed during extremely hot weather, installation of the protection course should take place within 24 hours.

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For additional information, refer to ASTM D6769, “Standard Guide for Application of Fully Adhered, Cold-Applied, Prefabricated Reinforced Modified Bituminous Membrane Waterproofing Systems.”

5.3 EPDM Membrane EPDM green roof waterproofing membranes consist of factoryfabricated sheets of ethylene propylene diene monomer (EPDM). Sheets are normally 45 mils to 60 mils thick; special thicknesses of 90 mils to 120 mils are available. It is recommended that a minimum 60-mil-thick reinforced membrane with stripped-in laps be used for waterproofing. EPDM membrane waterproofing should be adhered to the substrate, not mechanically attached or loose-laid. EPDM green roof waterproofing membranes should not be used in contact with bituminous cements and mastics. EPDM membrane sheets cannot be used in contact with certain acids, oils, grease and solvents. Contact the membrane manufacturer for specific details concerning these contaminants. EPDM green roof waterproofing membranes should generally not be installed when ambient temperatures are below 40 F. If installation is necessary at lower ambient temperatures due to project conditions, consult the manufacturer for specific coldweather application recommendations. EPDM membranes should only be used in conjunction with adhesives and tapes recommended by the membrane manufacturer. Installation should not proceed when moisture is present. Vulcanized-rubber (EPDM) sheet material should conform to the following recognized standard: Vulcanized-rubber Sheets (EPDM)

ASTM D6134, Type I

5.3.1 Installation Form-release agents and concrete-curing compounds must be compatible with the waterproofing materials being used or must be removed from the concrete surface by the responsible trade. The substrate must be structurally sound. Surfaces to receive EPDM membrane waterproofing must be broom-clean; adequately cured and dry; reasonably smooth; and free of dust, dirt, voids, cracks, sharp projections, oil and grease. Cracks 1⁄16 inch or wider should be reinforced separately with an additional layer of membrane, 6-inch minimum width, prior to the application of the primary membrane system. Large cracks may need to be routed and filled with sealant prior to installation of the additional layer of membrane. Concrete surfaces should be properly cured. The elapsed time between placement of concrete and installation of the waterproofing material will be as recommended by the material manufacturer. Masonry block surfaces should be parged or filled as recommended by the manufacturer. Suspended slabs to be waterproofed must be vented from underneath so that moisture can be dissipated. Horizontal surfaces should be sloped for drainage. Lay the membrane on the substrate or a flat surface and allow it to relax for a minimum of one-half hour before use. Clean

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membrane surfaces to be adhered of any dust, dirt and release agents as recommended by the manufacturer. Expansion joints and similar details should be installed according to the manufacturer’s recommendations. Use the base flashing material as recommend by the membrane manufacturer at the junction of vertical and horizontal surfaces and at penetrations. Construction details applicable to green roof systems are provided in the Green Roof System Construction Details section of this manual. NRCA strongly recommends horizontal green roof waterproofing membranes be water-tested to prove their integrity prior to permitting subsequent construction. It is recommended the water test be witnessed and the results confirmed in writing in case a problem arises after job completion. The definition and criteria for performing a water test and a suggested form for documenting a water test are included in the Appendixes in the Green Roof System Guidelines section of this manual. After the waterproofing test has been successfully completed, cover the membrane with a protection course, root barrier, drainage layer and/or moisture-resistant insulation. Avoid all unnecessary traffic on the completed system prior to installation of the remaining components. If surfaces are exposed to the sun or if the green roof waterproofing membrane is being installed during extremely hot weather, installation of the protection course should occur within 24 hours. For additional information, refer to ASTM D5843, “Standard Guide for Application of Fully Adhered Vulcanized Rubber Sheets Used in Waterproofing.”

5.4 Polyvinyl Chloride (PVC) Membrane PVC green roof waterproofing membranes consist of factoryfabricated sheets of reinforced polyvinyl chloride. Sheets are normally 60, 80 and 96 mils thick. NRCA recommends PVC membranes for green roof systems be reinforced, 80-mils minimum thickness with stripped-in laps for waterproofing. PVC membrane waterproofing should be adhered to the substrate, not mechanically attached or loose-laid. PVC green roof waterproofing membranes should generally not be installed when ambient temperatures are below 40 F. If installation at lower temperatures is necessary due to project conditions, consult the manufacturer for specific cold-weather application recommendations. Installation should not proceed when moisture is present. The completed membrane should not be exposed to prolonged periods of sunlight before covering or backfilling to prevent slipping. PVC materials are not compatible with polystyrene insulation products and certain bitumen-based products, such as coal tar. Consult the manufacturer of the PVC membrane to verify compatibility with other substrates. Currently, there are no ASTM material standards for PVC sheet waterproofing materials.

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5.4.1 Installation Form-release agents and concrete-curing compounds must be compatible with the waterproofing materials being used or must be removed from the concrete surface by the responsible trade. The substrate must be structurally sound. Surfaces to receive PVC membrane waterproofing must be broom-clean; adequately cured and dry; reasonably smooth; and free of dust, dirt, voids, cracks, sharp projections, oil and grease. Cracks 1⁄16 inch or wider should be reinforced separately with an additional layer of membrane, 6-inch minimum width, prior to the application of the primary membrane system. Large cracks may need to be routed and filled with sealant prior to installation of the additional layer of membrane. Concrete surfaces should be properly cured. The elapsed time between placement of concrete and installation of the waterproofing material will be as recommended by the material manufacturer. Masonry block surfaces should be parged or filled as recommended by the manufacturer. Suspended slabs to be waterproofed must be vented from underneath so that moisture can be dissipated. Horizontal surfaces should be sloped for drainage. Lay the membrane on the substrate or a flat surface and allow it to relax for a minimum of one-half hour before use. Clean membrane surfaces to be adhered of any dust, dirt and release agents as recommended by the manufacturer. Expansion joints and similar details should be installed according to the manufacturer’s recommendations. Use the base flashing material as recommend by the membrane manufacturer at the junction of vertical and horizontal surfaces and at penetrations. Construction details applicable to green roof systems are provided in the Green Roof System Construction Details section of this manual.

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ers are modified with coal tar or asphalt. There are different grades of product for horizontal, vertical and special applications. NRCA recommends that one- and two-component fluidapplied elastomeric membranes be fabric-reinforced. The material cures to form a monolithic waterproof membrane. Single-component elastomers eliminate the need for mixing products at the job site. Two-component materials require job-site mixing but cure faster in cooler weather and under higher humidity conditions than one-component materials. Fluid-applied elastomeric green roof waterproofing membranes should not be used on exposed surfaces unless the product is UV-resistant or a compatible UV-protective coating is used. These materials cannot be applied to damp or contaminated surfaces. Two-component materials require proper mixing at the job site and have limited pot life after mixing. Fluid-applied elastomeric green roof waterproofing membranes should generally not be installed when ambient temperatures are below 40 F. If installation at lower temperatures is necessary due to project conditions, consult the manufacturer for specific cold-weather application recommendations. Installation should not proceed when moisture is present. Fluid-applied elastomeric green roof waterproofing membranes should conform to the following recognized standard: High-solids Elastomeric Membrane

ASTM C836 ASTM C957

Neoprene and Chlorosulfonated Polyethylene

ASTM D3468

5.5.1 Installation

Elastomeric Membranes

Form-release agents and concrete-curing compounds must be compatible with the waterproofing materials being used or must be removed from the concrete surface by the responsible trade. The substrate must be structurally sound. Surfaces to receive fluid-applied elastomeric waterproofing must be broom-clean; adequately cured and dry; reasonably smooth; and free of holes, voids, cracks, sharp projections, oil and grease. Concrete surfaces should be finished with a light-steel trowel followed by a fine-hair broom. Cracks 1⁄16 inch or wider, control joints and construction joints should be addressed separately as recommended by the material manufacturer prior to the application of the primary membrane system. Large cracks may need to be routed and filled with sealant prior to installation of the primary membrane system. Concrete surfaces should be properly cured. The elapsed time between placement of concrete and installation of the waterproofing material will be as recommended by the material manufacturer. Masonry block surfaces should be parged or filled as recommended by the manufacturer. Suspended slabs to be waterproofed must be vented from underneath so that moisture can be dissipated. Horizontal surfaces should be sloped for drainage.

Fluid-applied elastomeric green roof waterproofing membranes consist of high-solids-content polyurethane elastomers in liquid form. Some products are made solely of polyurethane, and oth-

When required by the manufacturer, prime the substrate with a primer approved by the manufacturer, and allow it to dry. Apply the product by spray, roller, trowel or squeegee using a

NRCA strongly recommends horizontal green roof waterproofing membranes be water-tested to prove their integrity prior to permitting subsequent construction. It is recommended the water test be witnessed and the results confirmed in writing in case a problem arises after job completion. The definition and criteria for performing a water test and a suggested form for documenting a water test are included in the Appendixes in the Green Roof System Guidelines section of this manual. After the waterproofing test has been successfully completed, cover the membrane with a protection course, root barrier, drainage layer and/or moisture-resistant insulation. Avoid all unnecessary traffic on the completed system prior to installation of the remaining components. If surfaces are exposed to the sun or if the green roof waterproofing membrane is being installed during extremely hot weather, installation of the protection course should take place within 24 hours

5.5 One- and Two-component Fluid-applied

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grade of product consistent with the method of application. It is strongly recommended a reinforcement mat be embedded into a separate coat of liquid membrane over shrinkage or stress cracks. Apply the waterproofing system over the entire surface at the required thickness. Typical application consists of a base coat at a wet-film thickness of 60 mils; embedded fabric reinforcement; a top coat at a wet-film thickness of 60 mils; and a protection board. Reinforcement is required at the junction of horizontal and vertical surfaces and penetrations. The use of sealant, fabric sheet flashing, metal or additional membrane may be required at these locations. Expansion joints and similar details should be installed according to the manufacturer’s recommendations. Use the base flashing material as recommend by the membrane manufacturer at the junction of vertical and horizontal surfaces and at penetrations. Construction details applicable to green roof systems are provided in the Green Roof System Construction Details section of this manual. NRCA strongly recommends horizontal green roof waterproofing membranes be water-tested to prove their integrity prior to permitting subsequent construction. It is recommended the

Figure 6: Common components used within a green roof system

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water test be witnessed and the results confirmed in writing in case a problem arises after job completion. The definition and criteria for performing a water test and a suggested form for documenting a water test are included in the Appendix in the Green Roof System Guidelines section of this manual. After the waterproofing test has been successfully completed, cover the membrane with a protection course, root barrier, drainage layer and/or moisture-resistant insulation. Avoid all unnecessary traffic on the completed system prior to installation of the remaining components. If surfaces are exposed to the sun or if the green roof waterproofing membrane is being installed during extremely hot weather, installation of the protection course should take place within 24 hours.

6. System Components NRCA recommends a green roof system incorporate a fully adhered green roof waterproofing membrane, protection course, root barrier, drainage layer, moisture-resistant insulation, aeration layer, moisture-retention layer, reservoir layer, filter fabric layer and an engineered soil-based growth medium with plantings. It is recommended the components in Figure 6 be installed above the membrane following the layered sequence as shown.

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6.1 Protection Course A protection course protects the membrane from damage after installation of the membrane. Damage can be caused by the installing contractors, as well as other trades that are on the project. A protection course is a separate layer of material installed on top of the membrane. The protection course material depends on the membrane type, and the thickness of the protection course depends on the overburden type. The following materials may be used for a protection course provided they are compatible with the system components: • Asphaltic boards, 1⁄8 or 1⁄4 inch thick, typically 4- by 8-foot sheets • Asphaltic sheets, typically a modified base sheet packaged in rolls • Extruded polystyrene (XPS) boards • PVC sheets

6.2 Root Barrier A root barrier is a material that prevents migration of plant roots from damaging the membrane. As many types of roots grow, they can penetrate the green roof waterproofing membrane and potentially create leak locations. A root barrier is typically a separate layer of material installed on top of the protection course, but it may be combined with a protection course or drainage course. The root barrier material type depends on the type of membrane and plants used for a green roof system. The following materials may be used as a root barrier: • High-density polyethylene (HDPE) boards, with heat-welded seams • Granulated modified bitumen membranes with root-inhibiting additives (e.g., copper sulphates) and heat-welded seams • Polyethylene sheets, 10 mils minimum, with unsealed overlaps of 5 feet minimum or sealed laps of 1 foot minimum

6.3 Drainage Layer A drainage course provides a location for moisture to move laterally through the green roof system. These products enhance the performance of the waterproofing material by relieving hydrostatic pressure from the material surface and the associated weight. The following are the most common types of drainage layers: • Drainage mat • Insulating drainage panels A drainage mat consists of waffle-like plastic core material factory-laminated with a specific filter fabric. Some drainage mats protect the waterproofing material from damage during overburden installation or may offer additional insulation to the

The NRCA Green Roof Systems Manual—2007 Edition

structure being waterproofed. Geotextile filter fabrics are used with these products to prevent soil fines from clogging the drainage mat and restricting drainage. Some drainage mats are “sided,” meaning one side must go up and the other side must go down. Designers specifying drainage mat should select materials with appropriate compressive strength for the waterproofing system. The flow rate of the drainage mat should be appropriate for the expected quantities of water, and the run-off should be removed by a drainage system. Typically, the drainage system (e.g., drain pipes, drain bowls) is not installed by the green roof system contractor. Insulating drainage panels consist of high-density, moistureresistant insulation boards with grooved drainage channels on one face that are covered with a geotextile. Panels provide protection for waterproofing, thermal insulation and drainage for water. Panels are held in place with adhesives or stick clips. Drainage from one roof area to another roof area may not be appropriate. At a minimum, drainage from one roof area to another roof must be accounted for in the overall drainage amounts. NRCA suggests all green roof systems be drained internally because of NRCA’s recommendation to incorporate structurally sound perimeter containment, such as a parapet wall.

6.4 Moisture-resistant Insulation NRCA recommends XPS insulation be used as insulating material for green roof systems. The R-value of XPS is 5.0 per inch of thickness. The compressive strength of XPS should be based on the expected loading requirements, such as the weight of soil, plants and vehicles; however, NRCA recommends a minimum of 40 psi compressive strength. Expanded polystyrene insulation (EPS) is recommended for use as fill material, not as the primary insulating material, to reduce the total weight of a green roof system and provide contour of the final surface. If EPS is used for green roof systems, NRCA recommends a minimum 2-pound density. EPS will retain water, and, therefore, the additional weight should be accounted for when determining the total dead load of the system. The Rvalue for 2-pound density EPS is 4.35 per inch. Polyisocyanurate board insulation should not be used as insulation for green roof systems above the green roof waterproofing membrane. If polyisocyanurate board insulation is used below a green roof waterproofing membrane for green roof systems, the compressive strength must be appropriate for the expected dead and live loads of the selected system. Additionally, NRCA recommends that a layer of rigid board, such as a water-resistant gypsum board or cementitious board, be fully adhered to mechanically attached or fully adhered insulation prior to installation of the membrane. NRCA recommends a minimum of 40 psi compressive strength for all insulations used above or below green roof waterproofing membranes used in green roof systems. NRCA recommends that moisture-resistant insulation always be installed above the membrane. This provides thermal protection for the membrane, reducing the overall temperature gradient

The NRCA Green Roof Systems Manual—2007 Edition

that a membrane experiences. It is suggested that adding additional insulation be considered because of the expected loss of R-value when insulation is located in a moist environment. The substrate should provide positive drainage. NRCA does not recommend flat or tapered insulation under the green roof waterproofing membrane. The insulation type and overall thermal resistance (i.e., Rvalue) can affect the plantings. In general, more insulation is required for green roof systems than is used for traditional roof systems. The additional insulation is necessary to maintain a more consistent temperature of the soil. The additional insulation reduces the heat loss from the building, keeping the soil medium/overburden’s temperature closer to outdoor temperatures. With too little R-value, the heat loss from the building can keep the soil and roots warm, which may not be conducive to plant life cycles, for example, possibly upsetting necessary dormant periods. Some buildings, such as unheated parking structures, may not require any insulation.

6.5 Aeration Layer Aeration layers are needed when insulation is used so the insulation will retain its R-value. An aeration layer allows air to move across the top surface of the insulation layer. Additionally, the aeration layer allows moisture to drain from the topside of the insulation. The composition of an aeration layer is similar to that of a drainage mat. Aeration layers generally consist of waffle-like plastic core material factory-laminated with a filter fabric. Geotextile filter fabrics are used with these products to prevent soil fines from clogging the aeration layer and restricting air and moisture flow. Designers specifying aeration layers should select materials with appropriate compressive strength for the green roof system. The flow rate (air and moisture) should be appropriate for adequate movement of air and moisture to retain the insulation’s R-value. Where insulation is used without an aeration layer, the inplace R-value of the insulation likely will be less than the design R-value of the insulation because of the moisture retained within the insulation.

6.6 Moisture-retention Layer

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overburden type but typically consist of polyethylene-based panels formed into a three-dimensional array of water reservoir cups and drainage channels. The panels are designed to hold a specific amount of moisture by use of overflow holes, which limit the capacity of the cups. The reservoir cups are graduated in size for differing amounts of water storage as required for the engineered soil-based growth medium and plantings. Reservoir layers typically include aggregate when used under intensive green roof systems due to the large water storage requirement. Steep-slope green roof systems may require a reservoir layer to prevent immediate drainage of water. Filter fabric may be manufactured as part of a reservoir layer but typically is not.

6.8 Filter Fabric Filter fabric, also known as “geotextile,” is a tightly woven fabric, typically polyester or polyethylene/polypropylene, used to restrict the flow of fine soil particles and other contaminants while allowing water to pass freely through, thereby protecting drainage systems from clogging. Filter fabric often is laid directly over the top surface of the drainage layer and is generally installed just prior to placement of the growth medium.

6.9 Engineered Soil-based Growth Medium Growth medium is typically an engineered soil-based medium and is specially formulated (engineered) to provide a proper growing environment for the specific plants to be included in a green roof system. Different plant combinations with specific characteristics are typically selected based on the depth of the green roof system overburden. Therefore, different plant combinations are used for extensive (shallow), semi-intensive (moderate depth) and intensive (deep) green roof systems. Components such as lava rocks, drainage rocks, expanded shale, pea gravel, sand and mushroom compost can be combined to provide specific moisture-holding characteristics of the growth medium. A mesh wind blanket may be installed over the growth medium to hold young plants in place. A green roof system manufacturer or landscape architect will typically determine the appropriate medium mix based on the specific variables of the project. Soil-based growth medium combined with plantings, walkways and other surface landscape features make up the overburden of a green roof system.

A moisture-retention layer retains or stores moisture for plant growth. The materials for a moisture-retention layer depend on the overburden type. A moisture-retention layer typically is an absorptive mat consisting of recycled polypropylene fibers. A moisture-retention layer is typically located above the drainage layer (or it can be combined with the drainage layer) in uninsulated systems or above the aeration layer in insulated systems.

Engineered soil-based growth mediums are mineral-based, organic-based or synthetic. The components are blended in appropriate ratios to provide the needed characteristics of the medium. Engineered soil-based growth medium considerations include vegetation requirements, moisture and nutrient retention, drainage, PH level, porosity and compaction, erosion resistance, weight restrictions based on structure, resistance to fire propagation and structure for plant anchorage.

6.7 Reservoir Layer

Consult the green roof system manufacturer or a landscaping architect for overburden design of soil and/or aggregate mixtures.

A reservoir layer retains or stores moisture for overburden growth. A reservoir layer is typically located above the moistureretention layer. The materials for a reservoir layer depend on the

There are green roof systems currently in the marketplace that use tray systems to provide the engineered soil-based growth medium and plantings. Tray systems are installed above the

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membrane, which may be installed over an insulation board layer. This type of green roof system closely resembles a traditional roof system with trays placed above the roof membrane. However, tray systems are not recommended for use as green roof systems by NRCA because of the possibility of damage to the membrane and concerns for uplift and UV resistance. If tray systems are used, some provision to provide uplift resistance should be included. The trays may be clipped together; a netting system may be used; or a tie-down system of some type may be used. It is recommended these systems be used only on low-rise buildings with low uplift pressures. It is recommended membranes used under tray systems be fully adhered to provide uplift resistance and also UV-resistant because the trays may be removed and the membrane exposed. Some tray systems are designed as ballast for loose-laid green roof systems; however, NRCA does not recommend the use of these systems because if the trays are removed, the system has no uplift resistance. Additionally, the trays should be placed on a protection layer of either insulation or protection board. There are tray systems that incorporate biodegradable trays that, over time, degrade to become extensive green roof systems. Provisions for uplift resistance must be accounted for while the trays degrade.

7. Accessories There are a number of system components that can be used as part of green roof systems. The following system components are available for use.

7.1 Inspection Boxes There are two types of inspection boxes: one for accessory items and one for drains. Inspection boxes are used to allow inspection of valves, fittings, electrical connections or areas within green roof systems that require periodic inspection and must be readily accessible. There are heavy-duty types of inspection boxes that can be walked and/or driven on. Inspection boxes do not have drainage through the edges. Inspection box extension elements are used to extend inspection boxes for intensive (deep) systems. Drainage inspection boxes are used to allow inspection of drains. They typically have removable or hinged covers and drainage through the edges, and they must be placed on the drainage layer. Both types of inspection boxes can be locked, have a top surface of natural stone and be insulated. Depending on the climatic region and what is in the inspection box, the location of the boxes can vary. They may be within, level with or above the medium.

7.2 Irrigation and Electrical Lines Irrigation and electrical lines are components often used in a green roof system. The installed location of these will vary and

The NRCA Green Roof Systems Manual—2007 Edition

depends on the type of green roof system installed. For green roof systems, irrigation and electrical lines should be located within the engineered soil-based growth medium. Irrigation and electrical lines should not be attached to the substrate through the membrane or flashings, and the lines should not rest directly on the membrane surface. For ease of maintenance, electrical lines may be located on top of the overburden. It is suggested locations of electrical lines be marked and protected due to the potential for damage by maintenance and overburden. Climatic conditions will generally guide the selection of the material(s) used for pipes for green roof systems. Pipe materials will generally be PVC or stainless steel. Common/standard galvanized conduit is not recommended due to its corrosion potential. NRCA recommends PVC piping be schedule 40 minimum and stainless steel be type 304 or type 316. NRCA recommends all buried metal be stainless steel type 304 or type 316. Copper is not recommended for use for pipes as part of a green roof system. Pipe can be buried or installed above the growth medium. Adequate compressive strength for buried pipes is necessary to prevent crushing of pipes. Pipe supports are used to carry pipes that are installed above the medium, or exposed. Exposed pipes are typically carried on roller supports to prevent abrasion from expansion and contraction of the pipes. Pipes may also be buried in the medium to minimize expansion and contraction to some extent. Pipes should never be run through scuppers under any conditions.

7.3 Overburden Dividers and Terminations Overburden dividers include gravel boards, edge pieces, rounded edge sections and green roof edge terminations. They are used to separate overburden types, such as soil and pavers or soil and rock; they are installed over the drainage layer, and they can be polyethylene (vertical piece with support stands) or stainless steel (L- or T-shaped). Overburden dividers are not mechanically fastened but are loose-laid and ballasted with overburden and typically have drainage slots.

7.4 Drain Systems Green roof systems generally are designed to capture and retain water to some extent. This is a unique characteristic of a green roof system. Some moisture will drain through the overburden to the drainage layers above the membrane. Moisture will be transported to roof drains via the drainage layer(s). Drain systems incorporate roof drains with clamping rings and strainers. Where possible, drains should be capable of removing water from a green roof system at surfaces above the waterproofing layer in addition to removing water at the waterproofing layer. Drains with perforated enclosures provide this function. Surface drains are typically square drainage boxes with grating as the top surface; they need to be tied to drainage pipes. Bilevel drains are used for balconies and terraces. Bi-level drains drain vertically into a substrate drain.

The NRCA Green Roof Systems Manual—2007 Edition

7.5 Metal Components Exposed metal, such as counterflashing and overburden dividers, can be stainless steel, prefinished aluminum or prefinished galvanized steel. It is recommended that the service life of all metal components be the same or longer than the expected service life of the green roof system. Copper is not recommended for use as part of a green roof system. It should not be embedded within the overburden (as piping) or used as counterflashing for flashing. Runoff from copper roofs should be prevented from contaminating a green roof system, either by redirecting or eliminating the runoff or by containing the runoff.

7.6 Area Dividers Waterproofing system area dividers can be incorporated into a green roof system to segment larger areas of waterproofing into smaller areas or to separate different types of waterproofing and/or roof systems. They also assist with containing leaks (if they occur) and help with repairs and maintenance. It is recommended that area dividers for green roof systems be constructed of stainless steel or concrete only. A waterproofing system area divider must be mechanically attached or fastened to the deck and properly flashed into the waterproofing system. Area dividers typically are constructed in a grid pattern. They should not block the flow of water and will require drainage components within each individual grid of the system.

8. Design Considerations 8.1 System Assemblies Green roof system contractors generally are not professional landscape contractors, and specific discussion regarding soil, plants and vegetation is outside the scope of this document. NRCA believes it is typically the green roof system designer’s responsibility to design the green roof waterproofing membrane system, protection course, root barrier, drainage layer, moisture-resistant insulation layer, aeration layer, moisture-retention layer and reservoir layer, relative to the selected engineered soil and plantings. Some green roof system manufacturers provide overburden types for specific systems. Consult the manufacturer for specific overburden types. Additionally, information may be available from green roof industry organizations.

8.2 Building Codes As with all construction projects, green roof systems must meet the applicable local building codes. NRCA is not aware of any green roof system that has been tested for fire resistance (Class A, Class B or Class C) or wind resistance. However, a green roof system that includes a fireresistance-rated membrane is generally considered to be acceptable for use.

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A majority of the U.S. has adopted the International Building Code. The following is provided as information only and not as a substitute for researching the full extent of the applicable building code. The International Building Code, 2006 Edition, states in Section 1607.11.2.3, “Where roofs are to be landscaped, the uniform design live load in the landscaped area shall be 20 psf (0.958 kN/m2). The weight of the landscaping materials shall be considered as dead load and shall be computed on the basis of saturation of the soil.”

8.3 Quality Assurance and Water Tests Continuous visual inspection during green roof waterproofing membrane and green roof system application provides a complete and meaningful means of examining workmanship practices. If part-time inspections are performed, the inspections should occur at the beginning and end of significant phases and when other construction trades’ work may affect the performance of the green roof system. The quality-assurance representative’s responsibilities should be clearly defined to ensure complete understanding of expectations of materials to be installed, installation methods and definition of deficiencies with appropriately defined corrective actions. The representative should, in a timely manner, provide a contractor with copies of all reports prepared for an owner and should orally inform the contractor’s field personnel of locations of items requiring corrective action at the time of observation. Quality assurance by the owner should continue after completion of the green roof waterproofing membrane until all overburden work is completed. NRCA strongly recommends horizontal green roof waterproofing membranes used as part of a green roof system be watertested to prove their integrity prior to permitting subsequent construction. It is recommended the water test be witnessed and the results confirmed in writing in case a problem arises after job completion. Refer to Section 14.2, Water-test Procedure, for additional information.

9. Low-slope vs. Steep-slope Green roof systems can be used for low- and steep-slope roof systems. Generally, only extensive (shallow) systems are used for steep-slope green roof systems, which NRCA defines as 2:12 and greater. The primary difference between low- and steep-slope green roof systems is the need to prevent erosion and slippage of the overburden. The use of edge retainers and erosion-control devices integral with the overburden is recommended. However, edge retainers and erosion-control devices should not be attached through the green roof waterproofing membrane.

10. Care and Maintenance by Green Roof System Contractor Maintenance on the waterproofing portion of a green roof system is limited to inspection of drains and exposed elements, such as drainage boxes and flashings. There typically is no

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maintenance performed on a green roof waterproofing membrane except at areas that remain exposed. For green roof systems with soil overburden, it is recommended that access ports be provided at the drain locations. Access ports, or inspection chambers, allow for the cleanout of drain lines and drain strainers. Access ports should also be provided at primary irrigation lines and electrical lines. Where grasses are used as the vegetation for a green roof system, side wall and penetration protection is needed above the top of the overburden where the membrane is exposed because of potential damage from mowers and mechanized landscaping equipment. The use of pavers or gravel to keep landscaping equipment away from side walls and penetrations also is effective protection. Electric field vector mapping is available to help determine the location of leaks should they occur during a water test or after the green roof system is completed. This low-voltage test uses water as a conductive medium and a wire-loop configuration to create an electrical potential difference between a nonconductive membrane surface and a conductive structural deck or substrate, which is grounded. By applying water on the membrane surface, an electric field is created, and breaches in the membrane create vectors (ground fault connections). These vectors enable technicians to locate green roof waterproofing membrane defects. This method can be configured to locate leaks within a green roof system.

11. Care and Maintenance by Landscaping Contractor A green roof system generally will require some type of annual or semiannual maintenance for the plantings. When replacing or replanting portions of the plants, removal of soil by shovels and/or mechanized equipment may occur. This may subject the existing green roof system components to damage. Caution should be taken so the growth medium is not allowed to drop beneath the filter fabric and possibly clog the drainage and reservoir components. If it becomes necessary to dislodge the green roof system components, NRCA recommends a green roof system contractor be contacted to repair any damage or displaced components. Removal of components below the overburden can be damaging to the performance of the green roof system. Fertilizers, chemicals and pesticides used in the vegetation portion of a green roof system should be compatible with or not adversely affect the waterproofing system components. It is recommended the designer determine whether the fertilizers, chemicals and pesticides used will harm the membrane. Check with the membrane manufacturer for compatibility issues. Building owners should provide appropriate information regarding the compatibility of fertilizers and chemicals to those responsible for maintaining the landscaping portion of a green roof system. Additionally, building owners should maintain accurate records, such as as-built drawings, soil thickness and the locations of electrical lines, irrigation lines, conduit and PVC piping.

The NRCA Green Roof Systems Manual—2007 Edition

12. Reroofing Guidelines for Green Roof Systems Reroofing an existing green roof system means replacing or refurbishing the green roof waterproofing membrane. This requires the removal and replacement of the engineered soilbased growth medium and plantings, as well as all removal and replacement of all components of the green roof system above the membrane. Reroofing a green roof system should always include the replacement or refurbishing of the green roof waterproofing membrane. This can provide an opportunity to inspect the deck and make any necessary repairs before installation of a new membrane.

13. Converting a Conventional Roof System to a Green Roof System For existing conventional roof systems, extensive (shallow) green roof systems can be relatively easily retrofitted as replacement green roof systems given certain circumstances. The structural capacity of the existing deck type is critical. NRCA strongly recommends a licensed structural engineer determine the structural capacity of the existing system and the appropriateness of using a specific green roof system as a replacement for a traditional roof system. Concrete decks are most likely to have the structural capacity to support a green roof system. If a replacement green roof system weighs similarly to the traditional roof system to be removed, structural capacity should be acceptable. For example, an existing ballasted single-ply roof system (approximately 10 to 12 pounds per square foot) can be replaced by an extensive (shallow) green roof system weighing an equivalent amount. The lightweight soil medium of an extensive (shallow) green roof system may make this a realistic possibility.

14. Appendixes 14.1 Guidelines and Standards Until recently, the only guidelines for green roof systems were those developed by the Forschungsgesellschaft Landschaftentwicklung Landschaftsbau. e.V. (FLL) in Germany. ASTM International’s Green Roof Task Force, E 06.71, is developing standards specifically for green roof systems and components. The standards that are currently available are as follows: • E2396, “Standard Test Method for Saturated Water Permeability of Granular Drainage Media [Falling-Head Method] for Green Roof Systems” • E2397, “Standard Practice for Determination of Dead Loads and Live Loads Associated With Green Roof Systems”

The NRCA Green Roof Systems Manual—2007 Edition

• E2398, “Standard Test Method for Water Capture and Media Retention of Geocomposite Drain Layers for Green Roof Systems” • E2399, “Standard Test Method for Maximum Media Density for Dead Load Analysis of Green Roof Systems” • E2400, “Standard Guide for Selection, Installation, and Maintenance of Plants for Green Roof Systems”

14.2 Water-test Procedure NRCA strongly recommends horizontal green roof waterproofing membranes used as part of a green roof system be water-tested to prove their integrity prior to permitting subsequent construction. It is recommended the water test be witnessed and the results confirmed in writing in case a problem arises after job completion. Before installation of overburden, a water test is conducted to evaluate whether a green roof waterproofing membrane is leakfree under hydrostatic (e.g., standing water) and/or nonhydrostatic conditions (e.g., flowing water). Prior to performing a water test, all appropriate parties and trades should be notified when the water test will occur. A water test is conducted in one of two ways: • A standing-water test is conducted by temporarily plugging or otherwise closing any deck drains and erecting temporary dams where required to retain water on the surface of the green roof waterproofing membrane and then flooding the surface to a maximum depth of 2 inches at the high point and retaining the water for a minimum of 24 hours or as required by the manufacturer. Installation and removal of any temporary dams should not damage the membrane. • A flowing-water test is conducted by applying continuously flowing water over the green roof waterproofing membrane’s surface—without closing drains or erecting dams—for a minimum of 24 hours or as required by the manufacturer. Selecting the correct water test depends on the structural capacity of the deck/substrate and the slope of the deck/ waterproofing system; however, job-site conditions may dictate the methodology of each project’s water test. Decks without significant slope can be water-tested using a flood test or a flowing-water test. Decks with significant slope (e.g., a steepslope green roof system) can be water-tested using a flowingwater test. Determining the structural capacity of the deck is the responsibility of the designer. Care must be taken so the weight of water retained does not exceed the load-carrying capacity of the structural deck and the height of the water does not exceed the height of the lowest flashing. The water should be allowed to remain on the green roof waterproofing membrane for a minimum of 24 hours for the flood test or for the flowing-water test or as required by the manufacturer, after which the areas beneath the membrane should be inspected for leaks. If leaks are detected, the test should be stopped, repairs made to the membrane and the area retested for a minimum of 24 hours. The protection course

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should be installed over the tested area after successfully completing the water test unless a protection course is an integral part of the green roof waterproofing membrane. The water test documents the performance of the green roof waterproofing membrane prior to placement of system components and overburden. After the waterproofing test has been successfully completed, cover the membrane with a protection course, root barrier, moisture-resistant insulation, and/or drainage course. Avoid all unnecessary traffic on the completed system prior to installation of the remaining components. If surfaces are exposed to the sun or if the green roof waterproofing membrane is being installed during extremely hot weather, installation of the protection course should occur within 24 hours. Other methods, such as electric field vector mapping, are available to help determine the location of leaks should they occur during a water test or after the green roof system is completed. The low-voltage test uses water as a conductive medium and a wire-loop configuration to create an electrical potential difference between a nonconductive membrane surface and a conductive structural deck or substrate, which is grounded. By applying water on the membrane surface, an electric field is created, and breaches in the membrane create vectors (ground fault connections). These vectors enable technicians to locate green roof waterproofing membrane defects. This method can be configured to locate leaks within a green roof system.

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14.3 Water-test Verification Form Name of Project: Project Address: ____________________________________________________________________________________________ City, State, ZIP: ______________________________________________________________________________________________ Test Location: ______________________________________________________________________________________________ ______________________________________________________________________________________________ Date: I Test Began: __________________(Date) ____________________(Time) I Test Ended: __________________(Date) ____________________(Time) I Test Duration: ________________________________________________ Test Conditions: I Standing-water Test: Minimum Height of Water: ________________________________Inches Maximum Height of Water: ________________________________Inches I Flowing-water Test: Remarks: ______________________________________________________________________________________ ______________________________________________________________________________________ ______________________________________________________________________________________ Test Results: No Leakage I Leakage Detected

I

Describe Location: ______________________________________________________________

________________________________________________________________________________________________ ________________________________________________________________________________________________ Retest Necessary

I

Yes / I

No

Witnesses: The following individuals representing the indicated companies witnessed either a portion of or all the above described water flood test and attest that the representations made here are true and accurate: Name:

Representing:

Signature:

__________________________________________________________________________________________________________ __________________________________________________________________________________________________________ __________________________________________________________________________________________________________

The NRCA Green Roof Systems Manual— 2007 Edition Green Roof System Construction Details

The NRCA Green Roof Systems Manual—2007 Edition

Introduction to Details The Green Roof System Construction Details section of this manual has been written to provide technical information concerning the design and installation of construction details for quality green roof systems. This introduction is intended to supplement the special notes on the individual construction details. Green roof system practices vary considerably in different parts of the U.S. because of the variety of conditions that exist and the various materials that are available for use. Many times, green roof systems are essentially customized, meaning they are designed for specific substrates and structures and applied on job sites. Adherence to the practices outlined in this manual is an option of each contracting firm. Area practices and the timeproven methods employed by individual firms are frequently given priority over these recommended general procedures. This manual defines green roof system, green roof assembly and waterproofing as follows: • Green roof system: a roof area of plantings/landscaping installed above a waterproofed substrate at any building level that is separated from the ground beneath it by a man-made structure. A green roof system consists of a waterproofing system and its associated components—such as protection course, root barrier, drainage layer, thermal insulation and aeration layer—and an overburden of growth medium and plantings. • Green roof assembly: a substrate and a green roof system. • Waterproofing: treatment of a surface or structure to prevent the passage of water under hydrostatic conditions. Green roof systems can be divided into three primary categories: intensive (shallow), semi-intensive (moderate depth) and extensive (deep), which are defined as follows: • Extensive (shallow) green roof system: green roof system with an engineered soil-based growth medium approximately 2 inches to 6 inches deep. • Semi-intensive (moderate depth) green roof system: green roof system with an engineered soil-based growth medium approximately 6 inches to 10 inches deep. • Intensive (deep) green roof system: green roof system with an engineered soil-based growth medium greater than 10 inches deep.

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Because of the wide variety of green roof system products, this manual cannot address all the different methods and practices for designing and installing all the products available to designers, contractors and building owners. In this manual, NRCA attempts to present the consensus of knowledgeable, practicing green roof system and waterproofing contractors throughout the U.S. as to the practices and procedures for good roofing and waterproofing. Where this manual provides specific suggestions or recommendations, it should be noted these may be more conservative approaches than may be commonly provided by individual product manufacturers, green roof system designers or green roof system contractors. The green roof system design and application procedures included in this manual are recognized to be sound and time-proven, and they apply throughout the U.S. The recommendations contained in the Green Roof System Construction Details section of this manual should not be construed as the only methods for designing and installing green roof systems. Some design criteria and application techniques may vary according to climatic conditions, and some geographical areas employ “area practices” that are sound and timeproven. NRCA does not mean to imply by any statement or exclusion that time-tested and proven area practices are unsatisfactory or inappropriate. Users of this manual are encouraged to contact NRCA members in the geographical areas for specific advice concerning area practices and current technical information. The Green Roof System Construction Details sections provides eight details showing generic depictions of green roof systems—extensive (shallow), semi-intensive (moderate depth) and intensive (deep)—with and without insulation and with different deck types. The remaining construction details are separated by green roof waterproofing membrane types. Detail specifics may need to be altered with other waterproofing membrane types and building-specific details. NRCA recommends that the Green Roof System Construction Details section of this manual be used in the design of green roof systems only after a number of criteria have been carefully considered, including: • Climate and geographical location • A building’s intended use and design life expectancy • Exterior and interior temperature, humidity and use conditions

The green roof system details provided in this manual provide design and installation information for:

• Code requirements

• Hot-fluid-applied polymer-modified asphalt membrane

• LEED™ considerations

• APP- and SBS-polymer-modified bitumen sheet membrane

• Type and condition of substrate

• EPDM membrane

• Structural system

• Polyvinyl chloride (PVC) membrane

• Slope and drainage

• One- and two-component fluid-applied elastomeric membrane.

• Green roof waterproofing membrane

The information contained in this manual is intended primarily to address new construction and retrofit green roof systems.

• Green roof system type (e.g., intensive [deep]), including overburden • Accessibility and building configuration

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The NRCA Green Roof Systems Manual—2007 Edition

• Building movement

where a membrane is exposed.

• Type and amount of insulation, protection and drainage needed

The green roof waterproofing membrane must be separated from materials that it is incompatible with. PVC membranes are incompatible with polystyrene insulations, which may be used as part of a green roof system. Separation is required at all locations where incompatible materials may come in contact with one another.

• Need for ventilation during installation • Compatibility with adjacent building and/or system components • Construction sequencing • Worker safety

Protection course

• Odors generated by certain system application methods

In some systems, the protection course and root barrier may be the same layer/material and may be installed in opposite (reversed) order.

• Snow loads, water retention loads

Root barrier

• Construction traffic

The selection of the root barrier is based on the type of plantings used in the green roof system. The location of the root barrier will vary based on system type and design considerations.

• Potential building additions

• Penetrations • Landscape maintenance These criteria play important roles in the ultimate success or failure of a green roof assembly and should be considered by a designer to determine the appropriate components of a green roof assembly, applicable products and specifications, and construction details to be used. In addition, a designer should be certain green roof material manufacturers’ requirements are taken into account, as well as requirements of applicable insurance, building code enforcement and/or other regulatory agencies. It is recommended the designer communicate with the manufacturer and consult material manufacturers’ specifications during the design of a green roof assembly. Specific to a green roof system’s construction details, NRCA recommends designers consider the following:

Structural decks NRCA recommends for all retrofit green roof systems, a structural deck inspection and structural capacity verification be required. All deficiencies in the deck must be corrected prior to installation of the green roof system. Wood plank decks may be used as substrates for green roof systems in retrofit projects. A gypsum or cementitious overlay board is required; structural capacity verification is required.

Green roof waterproofing membrane Ultraviolet (UV) protection, such as a metal covering, is required at all locations where membrane is exposed. Alternatively, use of a membrane that is unaffected by UV is required at all locations

Drainage layer The drainage layer below the moisture-resistant insulation has a geotextile layer on the topside. NRCA suggests all green roof systems be drained internally because of NRCA’s recommendation to incorporate structurally sound perimeter containment, such as a parapet wall.

Moisture-resistant insulation Moisture-resistant insulation is included in the details for installations over conditioned spaces. Over nonconditioned spaces, such as parking garages, insulation is typically not needed. Highdensity insulation with a high compressive strength is recommended for use in green roof systems.

Aeration layer The aeration layer above the insulation is needed to prevent the insulation from becoming saturated, which would lower its R-value. Aeration layers should not be absorptive or retain moisture. An aeration layer is needed if both insulation and moistureretention layers above the insulation are used. If insulation is not used, an aeration layer is not needed.

Moisture-retention layer The selection of the moisture-retention layer is based on the use and type of the reservoir and the type of plantings used in the green roof system.

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Reservoir layer

Drains

A reservoir layer is optional for an extensive (shallow) green roof system; however, a reservoir layer is required for semi-intensive (moderate depth) and intensive (deep) green roof systems. Intensive (deep) green roof systems may require aggregate in the reservoir layer.

All drains require an inspection chamber. Inspection chambers, if metal, should be stainless steel, or they should be made from a nonmetallic material that is noncorrosive. Additionally, all drains should have clamping rings.

If a green roof system does not include a moisture-retention layer, the reservoir layer may serve as the aeration layer; therefore, an aeration layer may be omitted in certain scenarios. The design/shape of the reservoir layer dictates this decision. A reservoir layer may not be appropriate under nonplanted areas because of weight concerns and the compressive strength of specific reservoir layer designs.

Filter fabric Filter fabric, also known as “geotextile,” is a tightly woven fabric, typically polyester or polyethylene/polypropylene used to restrict the flow of fine soil particles and other contaminants while allowing water to pass freely through; it is used to protect drainage systems from clogging. Filter fabric often is laid directly over the top surface of the drainage layer and is generally installed just prior to placement of the growth medium.

Engineered soil-based growth medium Details provided show an extensive (shallow) green roof system because the layering generally is the same for all system types. Semi-intensive (moderate depth) and intensive (deep) green roof systems details will need to be appropriately modified to accommodate the deeper growth medium and reservoir layer. Extensive (shallow) green roof systems have a growth medium typically 2 inches to 6 inches in depth. Semi-intensive (moderate depth) green roof systems have a growth medium typically 6 inches to 10 inches in depth. Intensive (deep) green roof systems have a growth medium typically greater than 10 inches in depth.

Counterflashings Copper is not recommended for use as sheet-metal counterflashings. Metal used for counterflashing needs to be compatible with the green roof waterproofing membrane and the engineered soil-based growth medium. Stainless steel, aluminum and galvanized sheet metal generally are acceptable.

Perimeters and edges Green roof systems should have 18- to 24-inch-wide pavers installed at all perimeters of a roof area. This allows for maintenance at flashings. Loose gravel is not recommended due to wind-resistance issues. NRCA suggests all green roof systems be drained internally because of NRCA’s recommendation to incorporate structurally sound perimeter containment, such as a parapet wall. Pavers are shown in the Construction Details because of uplift resistance issues. In certain locations, gravel fill can be substituted for pavers. Designers should verify that gravel fill at perimeters meets wind uplift requirements.

Penetrations and Clearance Green roof system drains and vertical sides of curbs often have particular installation or attachment requirements. Interior drain bowls and under-deck clamps typically are furnished and installed by others. Clamping rings and dome strainers generally are furnished by others and installed by a green roof system contractor. A maximum amount of space should be provided between pipes, walls and curbs to facilitate proper installation of membranes and flashings. NRCA recommends a minimum of 12 inches of clearance between pipes; a minimum of 12 inches of clearance between pipes and curbs or walls; and a minimum of 24 inches of clearance between walls and curbs. Waterproofing systems have different installation methods that may require different spacings, and certain project conditions may not allow for these recommended clearances. However, adequate space (i.e., clearance) is required for proper installation of the required flashings at these locations. Refer to Figure 7 for information.

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The NRCA Green Roof Systems Manual—2007 Edition

Figure 7: Guide for clearances between pipes, walls and curbs

Structural supports that penetrate vertically through the green roof waterproofing membrane preferably should be square or round. H-, L- and T-shaped structural supports are not preferred because they are difficult to flash properly and may be a constant maintenance problem.

Metal Flashing Components Figure 8 provides NRCA’s recommendations for counterflashing profiles.

The NRCA Green Roof Systems Manual—2007 Edition

Figure 8 (A and B): Options for termination of wall counterflashing

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54

Figure 8 (C and D): Options for termination of wall counterflashing

The NRCA Green Roof Systems Manual—2007 Edition

The NRCA Green Roof Systems Manual—2007 Edition

Figure 8 (E): Options for termination of wall counterflashing

Illustrations of metal components joinery, such as concealed or cover plates, are located in the sheet metal portion (Details SM-1 to SM-26) of the Construction Details section of The NRCA Roofing and Waterproofing Manual, Fifth Edition. NRCA does not recommend caulking the joint between the bottom of the exterior vertical face of a coping cap and building exterior because it does not add to the waterproofing integrity of the assembly and it may, in fact, hinder the ability of the wall construction to dissipate moisture. Proper gauge, girth and continuous cleat fastening should minimize wind-uplift damage. The bottom of the exterior vertical face of a coping cap should be a minimum of 1 inch below the uppermost edge of the exterior wall material.

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The NRCA Green Roof Systems Manual—2007 Edition

Figure 9: Guide for sheet-metal parapet cap (coping)

Metal Edge Uplift Resistance Uplift resistance of shop-fabricated sheet-metal parapet caps is based on the attachment of the front and back faces of the parapet cap. Figure 9 provides NRCA’s two recommendations for securement of contractor-fabricated sheet-metal parapet caps. NRCA’s approval listing with Intertek Testing Services/Warnock

Hersey is based on testing in accordance with ANSI/SPRI ES-1, “American National Standard for Edge Systems Used with Low Slope Roof Systems.” ANSI/SPRI ES-1 is a nationally recognized standard and is already referenced in several building codes, including the National Fire Protection Association’s NFPA 5000 and the International Building Code.

The NRCA Green Roof Systems Manual—2007 Edition

NRCA’s approval listing with FM Approvals is based on testing in accordance with FM 4435, “Roof Perimeter Flashing.” FM 4435 serves as the technical basis for FM’s approvals for roof perimeter flashings. This standard is also a specific requirement of the NFPA 5000 building code. NRCA has made separate arrangements with ITS and FM to allow NRCA member companies to be sublisted under NRCA’s approval listings. This allows sublisted NRCA member companies to fabricate and install listed edge-metal flashings in compliance with NRCA’s approval listings, ANSI/SPRI ES-1 and FM 4435. Additional information regarding these approval listings is available on NRCA’s Web site, www.nrca.net/rp/technical/details/.

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List of Details GR-1

Extensive (Shallow) Green Roof Systems With Insulation . . . . . . . . . . . . . . . .63

GR-2

Extensive (Shallow) Green Roof Systems Without Insulation

GR-3

Extensive (Shallow) Green Roof Systems With Insulation Over Steel Deck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65

GR-4

Extensive (Shallow) Green Roof Systems Without Insulation Over Steel Deck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66

GR-5

Semi-intensive (Moderate Depth) Green Roof Systems With Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67

GR-6

Semi-intensive (Moderate Depth) Green Roof Systems Without Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68

GR-7

Intensive (Deep) Green Roof Systems With Insulation . . . . . . . . . . . . . . . . . .69

GR-8

Intensive (Deep) Green Roof Systems Without Insulation . . . . . . . . . . . . . . . .70

GR-9

Wall Flashing for Hot-fluid-applied Waterproofing Membrane— Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . .71

. . . . . . . . . . . . .64

GR-10 Roof Drain for Hot-fluid-applied Waterproofing Membrane— Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . .72 GR-11 Low Parapet Flashing for Hot-fluid-applied Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . .73 GR-12 Continuous Pipe Penetration for Hot-fluid-applied Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . .74 GR-13 Plumbing Vent for Hot-fluid-applied Waterproofing Membrane— Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . .75 GR-14 Skylight, Scuttle and Smoke Vent for Hot-fluid-applied Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76 GR-15 Expansion Joint With Metal Cover for Hot-fluid-applied Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77 GR-16 Door Threshold Flashing for Hot-fluid-applied Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78 GR-17 Joint Details at Concrete Deck for Hot-fluid-applied Waterproofing Membrane for Green Roof Systems

. . . . . . . . . . . . . . . . . . .79

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The NRCA Green Roof Systems Manual—2007 Edition

GR-18 Joint Detail at Cementitious Board for Hot-fluid-applied Waterproofing Membrane for Green Roof Systems . . . . . . . . . . . . . . . . . . .80 GR-19 Wall Flashing for Modified Bitumen Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . .81 GR-20 Roof Drain for Modified Bitumen Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . .82 GR-21 Low Parapet Flashing for Modified Bitumen Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . .83 GR-22 Continuous Pipe Penetration for Modified Bitumen Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84 GR-23 Plumbing Vent for Modified Bitumen Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . .85 GR-24 Skylight, Scuttle and Smoke Vent for Modified Bitumen Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86 GR-25 Expansion Joint With Metal Cover for Modified Bitumen Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87 GR-26 Door Threshold Flashing for Modified Bitumen Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . .88 GR-27 Wall Flashing for Thermoset Waterproofing Membrane— Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . .89 GR-28 Roof Drain for Thermoset Waterproofing Membrane— Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . .90 GR-29 Low Parapet Flashing for Thermoset Waterproofing Membrane— Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . .91 GR-30 Continuous Pipe Penetration for Thermoset Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . .92 GR-31 Plumbing Vent for Thermoset Waterproofing Membrane— Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . .93 GR-32 Skylight, Scuttle and Smoke Vent for Thermoset Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . .94 GR-33 Expansion Joint With Metal Cover for Thermoset Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . .95

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GR-34 Door Threshold Flashing for Thermoset Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . .96 GR-35 Wall Flashing for Thermoplastic Waterproofing Membrane— Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . .97 GR-36 Roof Drain for Thermoplastic Waterproofing Membrane— Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . .98 GR-37 Low Parapet Flashing for Thermoplastic Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . .99 GR-38 Continuous Pipe Penetration for Thermoplastic Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . .100 GR-39 Plumbing Vent for Thermoplastic Waterproofing Membrane— Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . .101 GR-40 Skylight, Scuttle and Smoke Vent for Thermoplastic Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102 GR-41 Expansion Joint With Metal Cover for Thermoplastic Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103 GR-42 Door Threshold Flashing for Thermoplastic Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . .104 GR-43 Wall Flashing for Fluid-applied Elastomeric Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . .105 GR-44 Roof Drain for Fluid-applied Elastomeric Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . .106 GR-45 Low Parapet Flashing for Fluid-applied Elastomeric Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .107 GR-46 Continuous Pipe Penetration for Fluid-applied Elastomeric Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108 GR-47 Plumbing Vent for Fluid-applied Elastomeric Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . .109 GR-48 Skylight, Scuttle and Smoke Vent for Fluid-applied Elastomeric Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110

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GR-49 Expansion Joint With Metal Cover for Fluid-applied Elastomeric Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .111 GR-50 Door Threshold Flashing for Fluid-applied Elastomeric Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .112 GR-51 Joint Details at Concrete Deck for Fluid-applied Elastomeric Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113 GR-52 Joint Detail at Cementitious Board for Fluid-applied Elastomeric Waterproofing Membrane—Extensive (Shallow) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114 GR-53 Sidewall Penetration Flashing for Semi-intensive (Moderate Depth) and Intensive (Deep) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115 GR-54 Green Roof/Area Divider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116 GR-55 Paver Edge Options for Semi-intensive (Moderate Depth) and Intensive (Deep) Green Roof Systems . . . . . . . . . . . . . . . . . . . . . . . . .117

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The NRCA Green Roof Systems Manual— 2007 Edition Glossary

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Glossary

Application rate: the average quantity (mass, volume or thickness) of material applied per unit area.

Abrasion resistance: the ability to resist being worn away by contact with another moving, abrasive surface, such as foot traffic, mechanical equipment, wind-blown particles, etc.

Area divider: a raised, flashed assembly, typically a single- or double-wood member attached to a wood base plate that is anchored to the deck. It is used to accommodate thermal stresses in a waterproofing system where an expansion joint is not required or separate large roof areas or separate roof systems composed of different/incompatible materials; it may be used to facilitate installation of tapered insulation.

Absorption: the ability of a material to accept within its body quantities of gases or liquid, such as moisture. Accelerated weathering: the exposure of a specimen to a specified test environment for a specified time with the intent of producing in a shorter time period effects similar to actual weathering. Acid etch: in waterproofing, the use of a strong acid to remove the surface of concrete to expose the aggregate. Acrylic coating: a liquid coating system based on an acrylic resin. Generally, a latex-based coating system that cures by air drying. Acrylic resin: polymers of acrylic or methacrylic monomers. Often used as a latex base for coating systems. Active metal (anodic): a metal or material that readily gives up electrons to a cathodic (noble) material. (See anodic.) An active metal will corrode in the presence of moisture when in contact with a cathodic metal.

ARMA: Asphalt Roofing Manufacturers Association. Area practices: design or application techniques particular to a specific geographical region. ASHRAE: American Society of Heating, Refrigerating and AirConditioning Engineers. Asphalt: a dark brown or black substance found in a natural state or, more commonly, left as a residue after evaporating or otherwise processing crude oil or petroleum. Asphalt may be further refined to conform to various roofing and waterproofing grade specifications: Dead-level asphalt: a roofing asphalt conforming to the requirements of ASTM D312, Type I.

Adhesion: steady or firm attachment.

Flat asphalt: a roofing asphalt conforming to the requirements of ASTM D312, Type II.

Adhesive bond break: a material to facilitate independent movement between two units that would otherwise bond together.

Steep asphalt: a roofing asphalt conforming to the requirements of ASTM D312, Type III.

Aeration layer: commonly consists of waffle-like plastic core material factory-laminated to a filter fabric. An aeration layer allows air to move across the top surface of the insulation layer and is used so insulation will retain its R-value. Additionally, an aeration layer allows moisture to drain from the topside of the insulation.

Special steep asphalt: a roofing asphalt conforming to the requirements of ASTM D312, Type IV.

Aggregate: (1) crushed stone, crushed slag or water-worn gravel used for surfacing a built-up roof system; (2) any granular material. Aged R-value: thermal resistance value established by using artificial conditioning procedures for a prescribed time period. Air leakage: the unintended movement of air from a location where it is intended to be contained to another location. Aluminized steel: sheet steel with a thin aluminum coating bonded to the surface to enhance weathering characteristics. Aluminum: a nonrusting, malleable metal sometimes used for metal roofing and flashing. Anodic: a metal or material that readily gives up electrons to a cathodic material in the presence of an electrolyte. (See Galvanic series.) ANSI: American National Standards Institute. APA: American Plywood Association. APP: See Atactic polypropylene.

Waterproofing asphalt: a waterproofing asphalt conforming to the requirements of ASTM D449, Types I, II and III. Asphalt, air-blown: asphalt produced by blowing air through molten asphalt to raise its softening point and modify other properties. Asphalt emulsion: a mixture of asphalt particles and an emulsifying agent, such as bentonite clay and water. Asphalt felt: an asphalt-saturated and/or asphalt-coated felt. (See Felt.) Asphalt primer: See Primer. Asphalt roof cement: a trowelable mixture of solvent-based bitumen, mineral stabilizers, other fibers and/or fillers. Classified by ASTM D2822, Asphalt Roof Cement, and D4586 Asphalt Roof Cement, Asbestos-Free, Types I and II. Type I is sometimes referred to as plastic cement and is made from asphalt characterized as self-sealing, adhesive and ductile and conforming to ASTM D312, Type I; D449, Types I or II; or D946. (See Plastic cement and Flashing cement.) Type II is generally referred to as vertical-grade flashing cement and is made from asphalt characterized by a high softening point and relatively low ductility and conforming to the requirement of ASTM D312, Types II or III; or D449, Type III. (See Plastic cement and Flashing cement.)

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Asphaltene: a high-molecular-weight hydrocarbon fraction precipitated from asphalt by a designated solvent (paraffinic naphtha) at a specified temperature and solvent-asphalt ratio. ASTM: ASTM International, previously known as American Society for Testing and Materials. Atactic polypropylene: a group of high-molecular-weight polymers formed by the polymerization of propylene. Ballast: a material, such as aggregate or precast concrete pavers, that employs its mass and the force of gravity to hold (or assist in holding) single-ply roof membranes in place. Bar joist: See Steel joist. Barrier board: noncombustible board stock material of low thermal conductivity placed between two elements of a roof assembly. Base flashing (membrane base flashing): plies or strips of waterproofing membrane material used to close off and/or seal a roof at the horizontal-to-vertical intersections, such as at a roof/deck-to-wall juncture. Membrane base flashing covers the edge of the field membrane. (See Flashing.) Base ply: the bottom or first ply in a waterproofing membrane when additional plies are to be subsequently installed. Base sheet: an impregnated, saturated or coated felt placed as the first ply in some waterproofing systems. Between-slab membrane: a membrane installed over a structural deck that receives a topping surface. Bitumen: (1) a class of amorphous, black or dark-colored (solid, semi-solid or viscous) cementitious substances, natural or manufactured, principally composed of high-molecular-weight hydrocarbons, soluble in carbon disulfide, and found in asphalts, tars, pitches and asphaltenes; (2) a generic term used to denote any material composed principally of bitumen, typically asphalt or coal tar. Bitumen-stop: See Envelope or Bleed-sheet. Bituminous emulsion: a suspension of minute particles of bituminous material in water. Blanket (batt) insulation: glass fiber or other compressible fibrous insulation, generally available in roll form.

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Bond: the adhesive and/or cohesive forces holding two components in positive contact. Bond breaker tape: see Adhesive bond breaker. Boot: (1) a covering made of flexible material, which may be preformed to a particular shape, used to exclude dust, dirt, moisture, etc., from around a penetration; (2) a flexible material used to form a closure, sometimes installed at inside and outside corners. Brake: hand- or power-activated machinery used to bend metal. Bridging: when membrane or base flashing is unsupported at a juncture. British thermal unit (BTU): the heat energy required to raise the temperature of 1 pound of water 1 degree Fahrenheit (joule). For the metric equivalent, see Joule. Broadcast: uniformly cast or distribute granular or aggregate surfacing material. Brooming: to improve the embedding of a ply or membrane by using a broom or squeegee to smooth it out and ensure contact with the adhesive under the ply or membrane. Buckle: an upward, elongated displacement of a roof membrane frequently occurring over insulation or deck joints. A buckle may be an indication of movement within the roof assembly. Building code: The minimum construction requirements established generally by national organizations of experts and adopted completely or in altered form by local governing authorities. Built-up membrane: a continuous, semi-flexible membrane, consisting of multiple plies of saturated felts, coated felts, fabrics or mats assembled in place with alternate layers of bitumen, and surfaced with mineral aggregate, bituminous materials, a liquid-applied coating or a granule-surfaced cap sheet. Bun stock: large solid box-like structure formed during the production of polystyrene insulation; individual board stock pieces are then cut from the bun. Butt joint: a joint formed by adjacent, separate sections of material, such as where two neighboring pieces of insulation abut.

Bleed-sheet: a sheet material used to prevent the migration of bitumen.

Button punch: a process of indenting two or more thicknesses of metal that are pressed against each other to prevent slippage between the metal.

Blister: an enclosed pocket of air, which may be mixed with water or solvent vapor, trapped between impermeable layers of felt or membrane or between the membrane and substrate.

Butyl: rubber-like material produced by polymerizing isobutylene.

Blocking: sections of wood (which may be preservative-treated) built into a waterproofing assembly, usually attached above the deck and below the membrane or flashing, used to stiffen the deck around an opening, act as a stop for insulation, support a curb, or serve as a nailer for attachment of the membrane and/or flashing. Blowing agent: an expanding agent used to produce a gas by chemical or thermal action or both in manufacture of hollow or cellular materials.

Butyl coating: an elastomeric coating system derived from polymerized isobutylene. Butyl coatings are characterized by low water vapor permeability. Butyl rubber: a synthetic elastomer based on isobutylene and a minor amount of isoprene. It can be vulcanized and features low permeability to gases and water vapor. Butyl tape: a sealant tape sometimes used between metal roof panel seams and/or end laps; also used to seal other types of sheet metal joints and in various sealant applications.

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Calender: (1) to press between rollers or plates in order to smooth and glaze or to thin into sheets; (2) a machine for calendering. Camber: a slight convexity, arching or curvature (as of a beam, roof deck or road). Canopy: any overhanging or projecting roof structure, typically over entrances or doors. Cant strip: a beveled strip used under flashings to modify the angle at the point where the roofing or waterproofing membrane meets any vertical element. Cap flashing: (1) usually composed of metal, used to cover or shield the upper edges of the membrane base flashing or wall flashing; (2) a flashing used to cover the top of various building components, such as parapets or columns. (See Flashing and Coping.) Cap sheet: a sheet, often granule-surfaced, used as the top ply of some built-up or modified bitumen roof membranes and/or flashings. Capacitance meter: a device used to locate moisture or wet materials within a waterproofing system by measuring the ratio of the change to the potential difference between two conducting elements separated by a nonconductor. Capillary action: (1) the action by which the surface of a liquid where it is in contact with a solid is elevated or depressed depending on the relative attraction of the molecules of the liquid for each other and for those of the solid; (2) the siphoning of liquid into a joint or void between two adjacent surfaces. Catalyst: an ingredient that initiates a chemical reaction or increases the rate of a chemical reaction when combined with another chemical. Cathodic: a metal or material that readily attracts electrons from an anodic material in the presence of an electrolyte. (See Galvanic series). Caulk: a composition of vehicle and pigment used at ambient temperatures for filling/sealing joints or junctures; remains elastic for an extended period of time after application. Caulking: (1) the physical process of sealing a joint or juncture; (2) sealing and making weather-tight the joints, seams or voids between adjacent surfaces by filling with a sealant. Cavitation: the formation of a partial vacuum or cavity in a liquid. Cavity wall: an exterior wall, usually of masonry, consisting of an outer and inner wythe separated by a continuous airspace, but connected together by wire or sheet-metal tiles. C-channel: a structural framing member. Cellular glass insulation: a rigid closed-cell insulation board made from crushed glass and hydrogen sulfide gas. Cementitious board: cement-based board stock with moistureresistant, noncombustible core with cement as the primary binder that is used as a substrate board in a waterproofing or green roof system.

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Cementitious waterproofing: heavy cement-based compounds and various additives that are mixed and packaged for use in a dry form; the packaged mixture is then mixed with water and liquid bonding agents to a workable concrete-like consistency. Centipoise: a unit of measure of absolute viscosity. (The viscosity of water is one centipoise. The lower the number, the less viscous the material.) Centistoke: a unit of viscosity; the ratio of a liquid’s absolute viscosity to the density of that liquid. CERL: Construction Engineering Research Laboratory. Chalk: a powdery residue on the surface of a material. Chalk line: a line made on the roof or other flat surface by snapping a taut string or cord dusted with colored chalk. Chalking: the formation of a powdery surface condition from the disintegration of a binder or elastomer. Chemical resistance: the ability to withstand contact with specified chemicals without a significant change in properties. Chimney: stone, masonry, prefabricated metal or wood-framed structure, containing one or more flues, projecting through and above the roof. Chlorinated polyethylene (CPE): a thermoplastic material, used for single-ply roof membranes, composed of high-molecularweight polyethylene that has been chlorinated with a process that yields a flexible rubber-like material. Chlorosulfonated polyethylene (CSPE or CSM): probably best known by the DuPont trade name Hypalon,™ a synthetic, rubberlike thermoset material, based on high-molecular-weight polyethylene with sulphonyl chloride, usually formulated to produce a self-vulcanizing membrane. Classified by ASTM D5019. Cladding: a material used as the exterior wall enclosure of a building. Cleat: a continuous metal strip, or angled piece, used to secure metal components. (See Clip.) Clerestory: an upward extension of enclosed space created by carrying a setback vertical wall (typically glazed) up and through the roof slope. Two intersecting shed roofs on different planes. Clip: A noncontinuous metal component or angle piece used to secure two or more metal components together. (See Cleat.) Closure strip: a metal or resilient strip, such as neoprene foam, used to close openings created by joining metal panels or sheets and flashings. Coal tar: a dark brown to black-colored semi-solid hydrocarbon produced by the distillation of coal. Coal-tar pitch is further refined to conform to the following roofing grade specifications: Coal-tar pitch: a coal tar used as the waterproofing agent in dead-level or low-slope built-up roof membranes and membrane waterproofing systems, conforming to ASTM D450, Type I. Coal-tar waterproofing pitch: a coal tar used as the damp-

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proofing or waterproofing agent in below-grade structures, conforming to ASTM Specification D450, Type II. Coal-tar bitumen: a proprietary trade name for Type III coal tar used as the dampproofing or waterproofing agent in deadlevel or low-slope built-up roof membranes and membrane waterproofing systems, conforming to ASTM D450, Type III. Coal-tar felt: a felt that has been saturated or impregnated with refined coal tar. Coal-tar roof cement: a trowelable mixture of processed coal-tar base, solvents, mineral fillers and/or fibers. Classified by ASTM D4022, “Coal Tar Roof Cement, Asbestos Container.” Coated base sheet: a coated felt intended to be used as a base ply in a built-up or modified bitumen roof membrane. Coated fabric: fabrics that have been impregnated and/or coated with a plastic-like material in the form of a solution, dispersion hot-melt or powder. The term also applies to materials resulting from the application of a preformed film to a fabric by means of calendering. Coated felt (sheet): (1) an asphalt felt that has been coated on both sides with harder, more viscous asphalt; (2) a glass-fiber felt that has been simultaneously impregnated and coated with asphalt on both sides.

The NRCA Green Roof Systems Manual—2007 Edition

Compatible materials: two or more substances that can be mixed, blended or attached without separating, reacting or affecting the materials adversely. Composite board roof insulation: rigid board insulation generally comprised of perlite or wood fiberboard factory bonded to polyisocyanurate or polystyrene. Compounded thermoplastics: a category of roofing membranes made by blending thermoplastic resins with plasticizers, various modifiers, stabilizers, flame retardants, UV absorbers, fungicides and other proprietary substances alloyed with proprietary organic polymers. Compressive strength: the property of a material that relates to its ability to resist compression loads. Concealed plate: See Cover plate. Concrete slab: See Slab. Condense: to make denser or more compact, as when a material (e.g., water vapor) changes from its gas phase to its liquid phase. Condensate: the liquid resulting from the condensation of a gas. Condensation: the conversion of water vapor or other gas to liquid phase as the temperature drops; the act or process of condensing.

Coating: a layer of liquid material applied to a surface for protection or appearance.

Conditioning: the storage of a material specimen under specified temperature, humidity, etc., for a specified time prior to testing.

Cobwebbing: a phenomenon observed during spray application characterized by the formation of web-like threads along with the usual droplets leaving the spray gun nozzle.

Conductance, Thermal: the thermal transmission in unit time through unit area of a particular body or assembly having defined surfaces, when unit average temperature difference is established between the surfaces. C=Btu/h•ft2•F (C=W/m2•K).

Code: a collection of laws (regulations, ordinances or statutory requirements) adopted by governmental authority. (See Building code and Model code.) Coefficient of thermal expansion: the coefficient of change in dimension of a material per unit of dimension per degree change in temperature. Cohesion: the molecular forces of attraction by which the body of a material is held together. Coil coating: the application of a finish to a coil of metal using a continuous mechanical coating process. Cold forming: the process of shaping metal into desired profiles without the application of heat. Cold rolled: the process of forming steel into sheets, panels or shapes on a series of rollers at room temperature. Color stability: the ability of a material to retain its original color after exposure to weather. Column: in structures, a relatively long, slender vertical structural compression member such as a post, pillar or strut. Combustible: capable of burning. Combustion: a chemical process of oxidation that occurs at a rate fast enough to produce heat and usually light either as glow or flames; the process of burning.

Conductor head: an enlargement or catch basin at the top of a downspout or leader to receive rainwater from a gutter or scupper. Construction joint: (1) a joint where two successive placements of concrete meet; (2) a separation provided in a building that allows its component parts to move with respect to each other. Contact cements: adhesives used to adhere or bond various roofing components. These adhesives adhere mated components immediately on contact of surfaces to which the adhesive has been applied. Contamination: the process of making a material or surface unclean or unsuited for its intended purpose, usually by the addition or attachment of undesirable foreign substances. Control joint: a groove that is formed, sawed or tooled in a concrete or masonry structure to regulate the location and amount of cracking and separation resulting from the dimensional change of different parts of the structure, thereby avoiding the development of high stresses. Coping: the covering piece on top of a wall exposed to the weather, usually made of metal, masonry or stone and sloped to carry off water. Copolymer: the product of polymerization of two or more substances (as two different isomers) together.

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Copolymerization: a chemical reaction that results in the bonding of two or more dissimilar monomers to produce large, longchain molecules that are copolymers.

Cure: a process whereby a material is caused to form permanent molecular linkages by exposure to chemicals, heat, pressure and/or weathering.

Copper: a natural weathering metal used in metal roofing or flashing; typically used in 16-ounce-per-square-foot and 20ounce-per-square-foot thicknesses.

Cure time: the time required for a material to reach its desirable long-term physical characteristics.

Core cut or core sample: a sample from a waterproofing system taken for the purpose of obtaining primarily qualitative information about its construction. Typically, core-cut analysis can verify or reveal the type of membrane surfacing; the type of membrane; the approximate number of plies; the type, thickness and condition of the insulation (if any); and the type of deck used as a substrate for the roof system. Cornice: the decorative horizontal molding or projected roof overhang. Counterflashing: formed metal or elastomeric sheeting secured on or into a wall, curb, pipe, rooftop unit or other surface to cover and protect the upper edge of a base flashing and its associated fasteners. Course: (1) the term used for a row of material that forms the waterproofing or flashing system; (2) one layer of a series of materials applied to a surface (e.g., a five-course wall flashing is composed of three applications of roof cement with one ply of felt or fabric sandwiched between two layers of roof cement). Cover board: an insulation board used over closed-cell plastic foam insulation (e.g., polyisocyanurate) to prevent blistering when used in conjunction with hot bituminous membranes. Suitable cover-board insulations are glass-faced siliconized gypsum board, glass-fiber board, perlite board, wood-fiber board or mineral-fiber board. Cover boards are also recommended between polyisocyanurate insulation and single-ply membranes to protect the polyisocyanurate. Cover plate: a metal strip sometimes installed over or under the joint between formed metal pieces. Coverage: the surface area uniformly covered by a specific quantity of a particular material at a specific thickness. CPA: copolymer alloy. Crack: a nonlinear separation or fracture occurring in a material. Cricket: a relatively small area of a roof constructed to divert water from a horizontal intersection of the roof with a chimney, wall, expansion joint or other projection. (See Saddle.) Cross-linking: the formation of chemical bonds between polymeric chains. Cross-linking of rubber is referred to as vulcanization or “curing.” CRREL: Cold Regions Research and Engineering Laboratory. CSPE: chlorosulfonated polyethylene. Curb: (1) a raised member used to support waterproofing penetrations, such as skylights, mechanical equipment, hatches, etc., above the level of the waterproofing surface; (2) a raised waterproofing perimeter relatively low in height.

Cured concrete: concrete that has attained its intended design performance properties. Curing agent: an additive in a coating or adhesive that results in increased chemical activity between the components with an increase or decrease in rate of cure. Curing compound: a liquid that is sprayed or otherwise applied to newly placed concrete to retard the loss of water during curing. Cutback: solvent-thinned bitumen used in cold-process roofing adhesives, roof cements and roof coatings. Cutoff: a permanent detail designed to prevent lateral water movement in an insulation system and used to isolate sections of a waterproofing system. (Note: A cutoff is different from a tiein, which may be a temporary or permanent seal. See Tie-in.) Dead level: absolutely horizontal or zero slope. (See Slope.) Dead-level asphalt: See Asphalt. Dead loads: the weight of a structure itself, including the weight of fixtures or equipment permanently attached to it. Deck: a structural component of a building. The deck must be capable of safely supporting the design dead and live loads, including the weight of the roof or waterproofing systems, and the additional live loads required by the governing building codes and provide the substrate to which the roofing or waterproofing system is applied. Decks are either noncombustible (e.g., corrugated metal, concrete or gypsum) or combustible (e.g., wood plank or plywood). Deflection (bowing, sagging): (1) the deformation of a structural member as a result of loads acting on it; (2) any displacement in a body from its static position, or from an established direction or plane, as a result of forces acting on the body. Degradation: a deleterious change in the chemical structure, physical properties or appearance of a material from natural or artificial exposure (e.g., exposure to radiation, moisture, heat, freezing, wind, ozone, oxygen, etc.). Degree days: a unit used in estimating the fuel consumption for a building; equal to the number of degrees that the mean temperature, for a 24-hour day, is below the “base temperature”; the base temperature is taken as 65 F in the U.S. Delamination: separation of the laminated layers of a component or system. Design loads: the total load on a structural system for the most severe combination of loads and forces that it is designed to sustain. Dew-point temperature: the temperature at which air becomes saturated with water vapor. The temperature at which air has a

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relative humidity of 100 percent. Diaphragm: a floor slab, metal wall panel, roof panel, etc., having a sufficiently large in-plane shear stiffness and sufficient strength to transmit horizontal forces to resisting systems. Diffusion: the movement of water vapor from regions of high concentration (high water vapor pressure) toward regions of lower concentration. Dimensional stability: the degree to which a material maintains its original dimensions when subjected to changes in temperature and humidity. DOE: U.S. Department of Energy. Downspout: a vertical pipe or conduit used to carry runoff water from a scupper, conductor head or gutter of a building to a lower roof level or to the ground or storm-water runoff system. Drag load: the external force (e.g., from the weight of ice and snow) applied to a steep-slope roof system component forcing the component downslope. Drain: an outlet or other device used to collect and direct the flow of runoff water from a roof or waterproofing area. (See Primary drainage and Secondary drainage.) Drainage mat: a fabric composite or a nondegradable plastic configured to allow drainage of water, typically with adhered filter fabric to prevent soil and fines from blocking the drainage path. Drainage course: a separate layer of material that provides a location for moisture to move laterally through a green roof system. A drainage course relieves hydrostatic pressure from a material’s surface and the associated weight of water. Drainage system: prefabricated materials that facilitate the drainage of water away from the structure. Drip edge: a metal flashing or other overhanging component with an outward projecting lower edge, intended to control the direction of dripping water and help protect underlying building components. Dry: (1) free or relatively free from a liquid, especially water; (2) to remove water or moisture. Dry bulb temperature: the temperature of air as measured by an ordinary thermometer. Dry film thickness: the thickness, expressed in mils, of an applied and cured coating or mastic. For comparison, see Wet film thickness. Drying time: the time required for the loss of volatile components so that the material will no longer be adversely affected by weather conditions such as dew, rain or freezing. Dual level drain: in waterproofing, an outlet or other device with provisions for drainage at both the wearing surface and waterproofing membrane levels used to collect and direct the flow of runoff water from a horizontal slab. Dynamic load: any load that is nonstatic, such as a wind load or moving live load.

The NRCA Green Roof Systems Manual—2007 Edition

ECH: polyepichlorohydrin, commonly referred to as epichlorohydrin. (See Epichlorohydrin.) Edge stripping: membrane flashing strips cut to specific widths used to seal/flash perimeter edge metal and the membrane application of felt strips cut to narrower widths than the normal feltroll width to cover a joint between metal perimeter flashing and built-up waterproofing. EIP: ethylene interpolymer. Elasticity: the property of a body that causes it to tend to return to its original shape after deformation (as stretching, compression or torsion). Elastomer: a macromolecular material that returns rapidly to its approximate initial dimensions and shape after substantial deformation by a weak stress and subsequent release of that stress. Elastomeric coating: a coating that is capable of being stretched at least twice its original length (100 percent elongation) and recovering to its original dimensions. Elastomeric waterproofing: a liquid-applied single- or multicomponent waterproofing membrane that is seamless, flexible, and capable of being stretched at least twice its original length (100 percent elongation) and recovering to its original dimensions. Elongation: the ratio of the extension of a material to the length of the material prior to stretching. Embedment: (1) the process of pressing/positioning a felt, aggregate, fabric, mat or panel into hot bitumen or adhesive to ensure intimate contact at all points; (2) the process of pressing/positioning granules into coating in the manufacture of factory-prepared roofing, such as shingles; (3) the process of broadcasting aggregate into a waterproof coating for a nonskid surface. Embrittlement: the loss of flexibility or elasticity of a material. End lap: the distance of overlap where one ply, panel or piece extends beyond the end of the immediately adjacent underlying ply, panel or piece. Engineered soil-based growth medium: a soil-based medium specially formulated (engineered) to provide a proper growing environment for the specific plants to be included in a green roof system. Envelope (bitumen-stop): a continuous membrane edge seal formed at the perimeter and at penetrations by folding the base sheet or ply over the plies above and securing it to the top of the membrane. The envelope prevents bitumen seepage from the edge of the membrane. EPDM: ethylene propylene diene monomer (See Ethylene propylene diene terpolymer.) Epichlorohydrin (ECH): a synthetic rubber including two epichlorohydrin-based elastomers. It is similar to and compatible with EPDM. Epoxy: a class of synthetic, thermosetting resins that produce tough, hard, chemical-resistant coatings and adhesives.

The NRCA Green Roof Systems Manual—2007 Edition

Epoxy injection: the injection of low-viscosity epoxy materials into substrate cracks or voids to restore the monolithic nature of the substrate, typically for concrete substrates. Equilibrium moisture content (EMC): the moisture content of a material stabilized at a given temperature and relative humidity, expressed as percent moisture by weight. Equiviscous temperature (EVT): the temperature at which a bitumen attains the proper viscosity for built-up membrane application. Equiviscous temperature (EVT) application range: the recommended bitumen application temperature range. The range is approximately 25 degrees Farenheit above or below the EVT, thus giving a range of approximately 50 degrees Farenheit. The EVT range temperature is measured in the mop cart or mechanical spreader just prior to application of the bitumen to the substrate. Equiviscous temperature (EVT) for asphalt: the recommended EVT for roofing asphalt (ASTM D312, Type I, II, III or IV) is as follows: Mop application: the temperature at which the asphalt’s apparent viscosity is 125 centipoise (0.125 Pa•s). Mechanical spreader application: the temperature at which the asphalt’s apparent viscosity is 75 centipoise (0.075 Pa•s). Note: To avoid the use of two kettles if there are simultaneous mop and mechanical spreader applications, the EVT for mechanical spreader application can be used for both application techniques. Equiviscous temperature (EVT) for coal tar: the recommended EVT for roofing coal tar (ASTM D450, Type I or III) is the temperature at which the coal tar’s apparent viscosity is 25 centipoise (0.025 Pa•s). Ethylene interpolymers (EIP): a group of thermoplastic compounds generally based on PVC polymers from which certain single-ply roofing membranes can be formulated. Ethylene propylene diene terpolymer (EPDM): designated nomenclature of ASTM for a terpolymer of ethylene, propylene and diene. EPDM material is a thermosetting synthetic elastomer. EVT: equiviscous temperature. Exotherm: heat generated by a chemical reaction. Expansion joint: a structural separation between two building elements that allows free movement between the elements without damage to the roof or waterproofing system. Exposure: the traverse dimension of an element or component not overlapped by an adjacent element or component in a waterproofing membrane. For example, the exposure of any ply in a waterproofing system may be computed by dividing the felt width, minus 2 inches, by the number of shingled plies; thus, the exposure of 36-inch-wide felt in a shingled, four-ply membrane should be approximately 81⁄2 inches. Extensive (shallow) green roof system: green roof system with an engineered soil-based growth medium approximately 2 inch-

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es to 6 inches deep Extrusion: a process in which heated or unheated material is forced through a shaping orifice (a die) in one continuously formed shape, as in film, sheet, rod or tubing. Fabric: a woven cloth or material of organic or inorganic filaments, threads, or yarns used for reinforcement in certain membranes and flashings. Factory seam: a splice/seam made by the manufacturer during the assembly of sections of materials into larger sheets/panels. Fading: any lightening of initial color. Fallback: a reduction in bitumen softening point, sometimes caused by refluxing or overheating in a relatively closed container. (See Softening point drift.) Fastener: any of a wide variety of mechanical securement devices and assemblies, including nails, staples, screws, cleats, clips and bolts, which may be used to secure various components of a waterproofing assembly. Felt: a flexible sheet manufactured by the interlocking of fibers with a binder or through a combination of mechanical work, moisture and heat. Felts are manufactured principally from wood pulp and vegetable fibers (organic felts), asbestos fibers (asbestos felts), glass fibers (glass-fiber felts or ply sheets) or polyester fibers. Felt machine (felt layer): a mechanical device used for applying bitumen and roofing felt or ply sheet simultaneously. Field seam: a splice or seam made in the field (not the factory) where overlapping sheets are joined together using an adhesive, splicing tape, or heat- or solvent-welding. Filler: a relatively inert ingredient added to modify physical characteristics. Fillet: a heavy bead of waterproofing compound or sealant material generally installed at the point where vertical and horizontal surfaces meet to create two wider angles at the base of a vertical flashing. Film: sheeting having a nominal thickness not greater than 10 mils (0.010 inches). Film thickness: the thickness of a membrane or coating. Wet film thickness is the thickness of a coating as applied; dry film thickness is the thickness after curing. Film thickness is usually expressed in mils (thousandths of an inch). Filter fabric: a tightly woven fabric, typically polyester or polyethylene/polypropylene, used to restrict the flow of fine particles and other contaminants while allowing water to pass freely through. It is used to protect drainage systems from clogging. Fin: a term used to describe a deck surface condition. A sharp raised edge (generally in concrete) capable of damaging a roof membrane or vapor retarder. Fine-mineral surfacing: water-insoluble, inorganic material, more than 50 percent of which passes through a No. 35 sieve. Used on the surface of various roofing materials and

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membranes to prevent sticking. Fire resistance: the property of a material or assembly to withstand fire or give protection from it. Fire-retardant-treated (FRT) plywood: plywood that has been impregnated, under pressure, with mineral salts; in the event of fire, the burning wood and salts emit noncombustible gases and water vapor instead of the usual flammable vapors. Fishmouth: (also referred to as an edge wrinkle) a half-cylindrical or half-conical opening or void in a lapped edge or seam, usually caused by wrinkling or shifting of ply sheets during installation.

The NRCA Green Roof Systems Manual—2007 Edition

Fly-in: method of application for roll materials by which the dry sheet is set into the bitumen or adhesive applied to the roof surface. FM Approvals (FM): a research and testing organization that classifies roofing components and assemblies for their fire, traffic, impact (hail), weathering and wind-uplift resistance for insurance companies in the U.S. Force: a strength or energy exerted or brought to bear; cause of motion or change. FPL: Forest Products Laboratory.

Flaking: in protective coatings, the detachment of small pieces of the coating film.

G-90: a designation for galvanized metal sheet, indicating 0.90 ounces of zinc per square foot, measured on both sides.

Flammable: subject to easy ignition and rapid flaming combustion.

Galvalume: trade name for a metal alloy coating that is composed of aluminum, zinc and silicone.

Flame retardant: a chemical used to impart flame resistance.

Galvanic action: an electrochemical action that generates electrical current between two metals of dissimilar electrode potential.

Flame spread: the propagation of a flame away from its source of ignition. Flammability: those characteristics of a material that pertain to its relative ease of ignition and ability to sustain combustion. Flange: the projecting edge of a rigid or semi-rigid component, such as a metal edge flashing flange. Flash point: the lowest temperature at which vapors above a volatile combustible substance ignite in air when exposed to a flame. Flashing: components used to weatherproof or seal waterproofing system edges at perimeters, penetrations, walls, expansion joints, valleys, drains and other places where the covering or waterproofing membrane is interrupted or terminated. For example, membrane base flashing covers the edge of the field membrane, and cap flashings or counterflashings shield the upper edges of the base flashing. Flashing cement: a trowelable mixture of solvent-based bitumen and mineral stabilizers that may include asbestos or other inorganic or organic fibers. Generally, flashing cement is characterized as vertical-grade, which indicates it is intended for use on vertical surfaces. (See Asphalt roof cement and Plastic cement.) Flashing collar: (sometimes referred to as a roof jack or flashing boot) an accessory flashing used to cover and/or seal soil pipe vents and other penetrations through the waterproofing. Fleece: mats or felts composed of fibers, sometimes used as a membrane backer. Flood (pour) coat: (1) the surfacing layer of bitumen into which surfacing aggregate is embedded on an aggregate-surfaced built-up roof; (2) the surfacing layer of bitumen for a built-up waterproofing membrane. Flood test: See Water test. Fluid-applied elastomer: a liquid elastomeric material that cures after application to form a continuous waterproofing membrane. Fluid-applied waterproofing: See Fluid-applied elastomer.

Galvanic series: a list of metals and alloys arranged according to their relative electrolytic potentials in a given environment. Galvanize: to coat steel or iron with zinc. Galvanized steel: steel coated with zinc for corrosion resistance. Gauge: a metal thickness measurement. Geocomposite: a prefabricated water drainage material used to relieve hydrostatic pressure against waterproofing and promote drainage. Geotextile: a tightly woven fabric used to restrict the flow of fine soil particles and other contaminants while allowing water to pass freely through; used to protect drainage systems from clogging. Girt: a horizontal beam that supports wall cladding between columns. Glass-fiber insulation: blanket or rigid board insulation, composed of glass fibers bound together with a binder, faced or unfaced, used to insulate roofs and walls. Glass felt: glass fibers bonded into a sheet with resin and suitable for impregnation with asphalt in the manufacture of bituminous waterproofing, roofing membranes and shingles. Glass mat: a thin mat of glass fibers with or without a binder. Glaze coat: (1) the top layer of asphalt on a smooth-surfaced built-up membrane; (2) a thin protective coating of bitumen applied to the lower plies or top ply of a built-up membrane when application of additional felts or the flood coat and aggregate surfacing is delayed. (See Flood coat.) Gloss: the shine, sheen or luster of a dried film. Grain: a unit of measure in the English System of units; 7,000 grains equals 1 pound; used as a measure of the weight of moisture in air. Granule: (also referred to as mineral or ceramic granule) opaque, natural or synthetically colored aggregate commonly

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used to surface cap sheets, shingles and other granule-surfaced roof coverings.

ing membranes by the application of heat (in the form of hot air or open flame) and pressure. (See Heat seaming.)

Gravel: coarse granular aggregate resulting from the natural erosion of rock.

Hem: the edge created by folding metal back on itself.

Gravel stop: a flanged device, frequently metallic, designed to prevent loose aggregate from washing off the roof and to provide a continuous finished edge for the roofing. Green roof assembly: substrate and a green roof system. Green roof system: roof area of plantings/landscaping installed above a waterproofed substrate at any building level that is separated from the ground beneath it by a man-made structure. A green roof system consists of a waterproofing system and its associated components—such as protection course, root barrier, drainage layer, thermal insulation and aeration layer—and an overburden of growth medium and plantings. Green roof system contractor: a professional waterproofing or roof system contractor familiar with the installation of green roof systems. Green roof waterproofing membrane: a continuous layer used as a treatment of a surface or structure to prevent the passage of water under hydrostatic conditions; used specifically for a green roof system. (See Waterproofing membrane.) Groundwater level: at a particular site, the level below which the subsoil and rock masses of the earth are fully saturated with water. Grout: a mixture of cement, sand and water used to fill cracks and cavities in masonry. Gutter: a channeled component installed along the downslope perimeter of a roof to convey runoff water from the roof to the drain leaders or downspouts. Gypsum board panels: board stock with noncombustible core primarily composed of gypsum that is commonly used as a barrier board thermal barrier or cover board in a roof assembly. Headlap: the distance of overlap measured from the uppermost ply or course to the point where it laps over the undermost ply or course. Heat flow: the quantity of heat transferred to or from a system in a unit of time. Heat fused: to be installed by heating the underside of the sheet with a propane torch or other heating device, melting the polymer-modified bitumen on the bottom side and adhering the sheet in the molten material. (See Heat seaming and Heat welding.) Heat seaming: the process of joining thermoplastic films, membranes or sheets by heating and then applying pressure to bring both materials in contact with each other. (See Heat welding.) Heat transfer: the transmission of thermal energy from a location of higher temperature to a location of lower temperature. This can occur by conduction, convection or radiation. Heat welding: method of melting and fusing together the overlapping edges of separate sheets or sections of polymer-modified bitumen, thermoplastics or some uncured thermoset waterproof-

Hoist: a mechanical lifting device. Holiday: an area where a liquid-applied material is missing or absent. Honeycomb: voids left in concrete resulting from failure of the mortar to effectively fill the spaces among coarse aggregate particles. Hot or Hot stuff: a worker’s term for hot bitumen. Hot rubberized asphalt: a waterproofing membrane consisting of a blend of asphalt, SBS rubber polymer and mineral stabilizer, used with or without reinforcing sheets. Hue: the subjective perception of color such as red, yellow, green, blue, purple or some combination; white, black or gray possess no hue. Humidity: the condition of the atmosphere with respect to water vapor. (See Relative humidity.) HVAC: heating, ventilating and air-conditioning equipment. Hydration: the chemical reaction by which a substance (such as Portland cement) combines with water, giving off heat to form a crystalline structure in its setting and hardening. Hydrocarbon: an organic chemical compound primarily containing the elements carbon and hydrogen. Hydrostatic pressure: the pressure equivalent to that exerted on a surface by a column of water of a given height. Hydrostatic pressure relief system: (1) see Drainage system; (2) a system of perimeter and/or under-slab drains used to regulate the hydrostatic pressure in the earth surrounding a belowgrade structure. Hydrostatic pressure slab: See Mat slab. Hygroscopic: attracting, absorbing and retaining atmospheric moisture. Hypalon®: a registered trademark of E.I. du Pont de Nemours & Co. for “chlorosulfonated polyethylene” (CSPE). (See Chlorosulfonated polyethylene.) Ignition temperature: the lowest temperature at which combustion will occur spontaneously under specific conditions. Impact resistance: resistance to fracture under the sudden application of an exerted force. Impregnate: in materials manufacture, to completely surround the fibers in a felt or mat with bitumen, with the spaces between the fibers partially or completely filled without a continuous coating of bitumen on the surface. Infrared thermography: the process of displaying variations of apparent temperatures (variation of temperature or emissivity or both) over the surface of an object by measuring variations in infrared radiance.

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Inorganic: being or composed of materials other than hydrocarbons and their derivatives, or matter that is not of plant or animal origin. Insect screen: wire mesh used to prevent insects from entering the building through ventilators, louvers or other openings. In-service R-value: thermal-resistance value established under installed conditions and measured over the expected service life of the material. Insulation: any of a variety of materials designed to reduce the flow of heat either from or into a building. (See Thermal insulation.) Intensive (deep) green roof system: green roof system with and engineered soil-based growth medium greater than 10 inches deep. Inverted roof membrane assembly (IRMA™): a patented, proprietary variation of the “protected membrane roof assembly” in which Styrofoam® brand insulation and ballast are placed over the roof membrane. IRMA™ and Styrofoam® are registered trademarks of The Dow Chemical Co. ISANTA: International Staple, Nail & Tool Association. Isocyanate: a highly reactive organic chemical containing one or more isocyanate (-N=C=0) groups. A basic component in SPF systems and some polyurethane coating systems. Isolation sheet: See slip sheet. Joist: any of the small timbers, metal or wood beams arranged parallel to one another and spanning from wall to wall to support a floor, ceiling or roof of a building. Joule: a unit of energy or work; equals the work done by a force of 1 newton, which acts over a distance of 1 meter in the direction of the force. k or k-value: thermal conductivity; the time rate of heat flow through a unit area of a homogeneous material in a direction perpendicular to isothermal planes induced by a unit temperature gradient. In English (inch•pound) units of measurement, it is the number of Btu that pass through a 1-inch thickness of a 1square-foot sample of material in one hour with a temperature difference between the two surfaces of 1 degree Farenheit. It is expressed as Btu•inch/h•ft2•°F. Kerf: (1) a slit or notch made by a saw or cutting torch; (2) the width of cut made by a saw or cutting torch. Kesternich test: simulates acid rain conditions by subjecting test specimens to a sulfur dioxide atmosphere, as well as condensing moisture for the purpose of evaluating rust/corrosion characteristics. Lagging: a structure of wood beams and steel support members used to restrain soil and attach blind-side waterproofing. Laitance: a weak layer of cement and aggregate fines on a concrete surface that is usually caused by an overwet mixture, overworking the mixture, improper or excessive finishing, or combination thereof. Laminate: to join layers of materials together using fusion; the

The NRCA Green Roof Systems Manual—2007 Edition

process of joining layers of materials together using adhesion. Lap: that part of a waterproofing or flashing component that overlaps or covers any portion of the same or another type of adjacent component. Lap cement: an asphalt-based roof cement formulated to adhere overlapping plies or asphalt roll roofing. Lap seam: occurs where overlapping materials are seamed, sealed or otherwise bonded. Lead: a soft, malleable, heavy metal; has a low melting point and a high coefficient of thermal expansion. Leader head: See Conductor head. Link seal: an engineered pressure-tight seal used to seal pipes to cast-in-place sleeves in walls and floors by using small expansion devices that create a compression seal between the pipe and the sleeve. Liquid-applied: application of bituminous cements, adhesives or coatings installed at ambient or slightly elevated temperatures. Liquid-applied built-up roof: a continuous, semi-flexible roof membrane, consisting of multiple plies of felts, mats or fabrics laminated together with alternate layers of roof cements and surfaced with a liquid-applied coating with or without aggregate surfacing. Live loads: temporary loads that the deck or roof structure must be designed to support, as required by governing building codes. Live loads are generally moving and/or dynamic or environmental (e.g., people, installation equipment, snow, ice or rain, etc.). Loose-laid membrane: a ballasted membrane that is attached to the substrate only at the edges and penetrations. Low-slope roofs: a category of roofs that generally includes weatherproof membrane types of roof systems installed on slopes at or less than 3:12 (14 degrees). Low temperature flexibility: the ability of a membrane or other material to resist cracking when flexed after it has been cooled to a low temperature. Marine-grade plywood: plywood that is made entirely of Douglas fir or Western Larch with all veneer plies being Grade B or better is sanded on both faces or includes medium- or highdensity overlay with maximum core-gap sizes of 1⁄8 inch; is exterior-rated with fully waterproof structural adhesive glue; and is not treated with resistance-decay chemicals. Where decay is a concern, it should be pressure-preservative treated. Masonry: construction, usually set in mortar, of natural building stone or manufactured units, such as brick, concrete block, adobe, glass block, tile, manufactured stone or gypsum block. Mastic: a thick adhesive material used as a cementing agent for holding waterproofing membrane in place. (See Asphalt roof cement). Mat: a thin layer of woven, nonwoven or knitted fiber that serves as reinforcement to a material or membrane. Material safety data sheet (MSDS): a written description of the

The NRCA Green Roof Systems Manual—2007 Edition

chemicals in a product and other pertinent data, including such things as safe handling and emergency procedures. In accordance with OSHA regulations, it is the manufacturer’s responsibility to produce an MSDS and the employer’s responsibility to communicate its contents to employees. Mechanically fastened membranes: generally used to describe membranes that have been attached at defined intervals to the substrate. Membrane: a flexible or semi-flexible roof covering or waterproofing whose primary function is to exclude water. Metal: any of various opaque, fusible, ductile and typically lustrous substances that are good conductors of electricity and heat. Metal rain collar: a metal counterflashing used to wrap a penetration and prevent water infiltration though the top of the penetration base flashing. Meter: unit of length measurement in the metric system; 1 meter is equal to 39.37 inches. Mil: a unit of measure, one mil is equal to 0.001 inches, often used to indicate the thickness of a roofing membrane. Mildew: a superficial growth produced on organic matter or living plants by fungi. Millimeter: a unit of measure equal to one thousandth (0.001) of a meter, or 0.03937 inches. Mineral fiber: insulation composed principally of fibers manufactured from rock, slag or glass, with or without binders. Mineral granules: See Granules. Mineral stabilizer: a fine, water-insoluble inorganic material used in a mixture with solid or semi-solid bituminous materials. Miter joint: a joint between two members at an angle to each other; each member is cut at an angle equal to half the angle of the junction; usually the members are at right angles to each other. Model (building) codes: a compilation of standards or codes established to provide uniformity in regulations pertaining to building construction. Modified bitumen: (1) a bitumen modified by including one or more polymers (e.g., atactic polypropylene, styrene butadiene styrene, etc.); (2) composite sheets consisting of a polymermodified bitumen often reinforced with various types of mats or films and sometimes surfaced with films, foils or mineral granules. Moisture-retention layer: commonly an absorptive mat consisting of recycled polypropylene fibers that retains or stores moisture for plant growth. Monolithic: formed from or composed of a single material; seamless. Monomer: a low-molecular-weight substance consisting of molecules capable of reacting with like or unlike molecules to form a polymer. Mop and flop: an application procedure in which elements (insu-

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lation boards, felt plies, cap sheets, etc.) are initially placed upside down adjacent to their ultimate locations; coated with adhesive or bitumen; and turned over and adhered to the substrate. Mopping: the application of hot bitumen with a mop or mechanical applicator to the substrate or plies of a bituminous membrane. There are four types of mopping: • Solid mopping: a continuous coating. • Spot mopping: bitumen is applied roughly in circular areas, leaving a grid of unmopped perpendicular areas. • Sprinkle mopping: bitumen is shaken onto the substrate from a broom or mop in a random pattern. • Strip mopping: bitumen is applied in parallel bands. Nailer: (sometimes referred to as blocking) a piece or pieces of dimensional lumber and/or plywood secured to the structural deck or walls to provide a receiving medium for the fasteners used to attach membrane or flashing. Neoprene: a synthetic rubber (polychloroprene) used in liquid and sheet-applied elastomeric roof membranes or flashings. Nesting: (1) the installation of new metal roof deck directly on top of an existing metal roof deck; (2) a method of reroofing with new asphalt shingles over existing shingles in which the top edge of the new shingle is butted against the bottom edge of the existing shingle. Newton (N): SI unit of measure for force. Night seal (or night tie-in): a material and/or method used to temporarily seal a membrane edge during construction to protect the assembly in place from water penetration. Usually removed when application is resumed. NIST: National Institute of Standards and Technology. Nitrile alloy: an elastomeric material of synthetic nonvulcanizing polymers. Nitrile rubber: a membrane whose predominant resinous ingredient is a synthetic rubber made by the polymerization of acrylonitrile with butadiene. Noble metal: a metal that readily receives electrons from an anodic metal (See Galvanic series). Nondestructive testing (NDT): a method to evaluate the disposition, strength or composition of materials or systems without damaging the object under test. Nonflammable: not easily ignited and not burning rapidly if ignited. Nonfriable: a material that, when dry, cannot be crumbled, pulverized or reduced to powder by hand pressure. Nonoxidizing: a material that resists oxidation in exterior exposures or accelerated weathering. Non-traffic bearing: for waterproofing purposes, a membrane system requiring some form of protection barrier and wearing surface.

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Nonvolatile content: the portion of a coating that does not evaporate during drying or curing under specified conditions, comprising the binder and, if present, the pigment. (The percent volatile content is obtained by subtracting the nonvolatile content from 100.) Nonwoven fabric: a textile structure produced by bonding or interlocking of fibers, or both, accomplished by mechanical, chemical, thermal or solvent means and combinations thereof. NRCA: National Roofing Contractors Association. Nylon: generic name for a family of polyamide polymers, used as a scrim in some fabric-reinforced sheeting. Open time: the period of time after an adhesive has been applied and allowed to dry, during which an effective bond can be achieved by joining the two surfaces. Organic: being or composed of hydrocarbons or their derivatives, or matter of plant or animal origin. Organic felt: an asphalt base material manufactured from cellulose fibers. ORNL: Oak Ridge National Laboratory. Osmosis: movement of a solvent through a semipermeable membrane into a solution of higher solute concentration that tends to equalize the concentration of solute on the two sides of the membranes. Overburden: any material installed on top of a waterproofing assembly. Overburden dividers: overburden dividers include gravel boards, edge pieces, rounded edge sections and green roof system edge definers. They are used to separate overburden types, such as soil and pavers or soil and rock; they are installed over the protection course, drainage layer and filter layer and can be polyethylene (vertical piece with support stands) or stainless steel (Lshaped). Overburden dividers are not mechanically fastened but are loose-laid and ballasted and typically have drainage slots. They are installed over the protection course, drainage layer and filter layer and should be secured to avoid displacement. Overflow drainage: component in a building drainage system used to protect against damage from a water load imposed by blocked or partially blocked primary drainage system (e.g., overflow scupper, overflow interior drain). Overspray: undesirable depositions of airborne spray. Ozone: a triatomic form of oxygen that is a bluish gas of pungent odor; is formed naturally in the upper atmosphere by a photochemical reaction with solar UV radiation. Ozone resistance: the ability of a material to resist the deteriorating effects of ozone exposure. Pallet: a platform (typically wooden) used for storing and shipping materials. Parapet wall: the part of a perimeter wall that extends above the deck. Parge: in masonry construction, a coat of cement mortar on the

The NRCA Green Roof Systems Manual—2007 Edition

face of rough masonry, the earth side of foundation and basement walls, or the like. Partially attached: a roof assembly in which the membrane has been “spot affixed” to a substrate, usually with an adhesive or a mechanical device. Parting agent: a material applied to one or both surfaces of a sheet to prevent blocking. Pascal: SI unit of measure for force per unit area; 1 Pa=1 N/m2. Pedestal: a support or base for waterproofing components such as pavers, pipes and small rooftop units. Peel strength: the average load per unit width required to separate progressively a flexible member from a rigid member or another flexible member. Penetration: (1) any construction (e.g., pipes, conduits, HVAC supports) passing through the waterproofing; (2) the consistency of a bituminous material expressed as the distance, in tenths of a millimeter (0.1 mm), that a standard needle penetrates vertically into a sample of material under specified conditions of loading, time and temperature. Perlite: an aggregate used in lightweight insulating concrete and preformed perlitic insulation boards formed by heating and expanding siliceous volcanic glass. Perm: See Permeance. Permeability: (1) the capacity of a porous material to conduct or transmit fluids; (2) the time rate of vapor transmission through unit area of flat material of unit thickness induced by unit vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions. The English (inch•pound) unit of measurement for permeability is gr/h•ft2•(in•Hg/in.), which is commonly referred to as “perm/inch” units. Permeance: (1) the rate of water-vapor transmission per unit area at a steady state through a material, membrane or assembly; (2) the time rate of wate-vapor transmission through unit area of flat material or construction induced by unit vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions. The English (inch•pound) unit of measurement for permeance is gr/h•ft2•in. Hg, which is commonly referred to as “perm” units. pH: a measure of the acidity or alkalinity of a solution, with neutrality represented by a value of 7; increasing acidity represented by increasingly smaller values; and increasing alkalinity represented by increasingly larger values. Phased application: the installation of a waterproofing system during two or more separate time intervals or different days. Application of surfacings at different time intervals is typically not considered phased application. (See Surfacing.) Phased construction: (1) the installation of a roof or waterproofing system during two or more separate time intervals or different days. Application of surfacings at different time intervals is typically not considered phased application. (See Surfacing.) (2) the installation of a waterproofing system out of sequence; (3) for the application of a built-up waterproofing

The NRCA Green Roof Systems Manual—2007 Edition

membrane (generally interior applications), where the upper three-ply sheets are installed at a right angle (90 degrees) to the lower two-ply sheets. Picture framing: a square or rectangular pattern of ridges in a membrane or covering over insulation or deck joints. Pigment: an insoluble compounding material used to impart color. Pinhole: a tiny hole in a coating, film, foil, membrane or laminate comparable in size to one made by a pin. Pipe boot: prefabricated flashing piece used to flash around circular pipe penetrations. Pitch: See Coal tar. Plastic cement: a roofing industry generic term used to describe asphalt roof cement that is a trowelable mixture of solvent-based bitumen, mineral stabilizers, and other fibers and/or fillers. Generally intended for use on relatively low slopes, not vertical surfaces. (See Asphalt roof cement and Flashing cement.) Plasticizer: a material incorporated in a material to increase its ease of workability, flexibility or distensibility. Plasticizer migration: in some thermoplastic membranes, the loss of plasticizer chemicals from the membrane, resulting in shrinkage and embrittlement of the membrane, typically PVC. Pliability: the material property of being flexible or moldable. Ply: a layer of felt or ply sheet in a built-up membrane waterproofing system. PMR: protected membrane roof. Polychloroprene: See Neoprene. Polyester: a polymer in which the repeated structural unit in the chain is of the ester type. Polyisobutylene (PIB): a product formed by the polymerization of isobutylene. Polymer: a macromolecular material formed by the chemical combination of monomers having either the same or different chemical composition. Polymer-modified bitumen: See Modified bitumen. Polymerization: a chemical reaction in which monomers are linked together to form polymers. Polypropylene: a polymer prepared by the polymerization of propylene as the sole monomers. Polyol: a polyhydric alcohol (i.e., one containing three or more hydroxyl groups, one component of polyisocyanurate and polyurethane compounds). Polyvinyl chloride (PVC): a synthetic thermoplastic polymer prepared from vinylchloride. PVC can be compounded into flexible and rigid forms through the use of plasticizers, stabilizers, fillers and other modifiers. Rigid forms are used in pipes; flexible forms are used in the manufacture of sheeting and waterproofing membrane materials.

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Polystyrene: a polymer prepared by the polymerization of styrene as the sole monomer. Pond: a surface that is incompletely drained. Pop rivet: a relatively small-headed pin with an expandable head for joining light-gauge sheet metal. Positive drainage: for waterproofing, the drainage condition in which consideration has been made during design for all loading deflections of the deck, and additional slope has been provided to ensure drainage. Pot life (Working life): the period of time during which a reacting composition remains suitable for its intended processing after mixing with reaction-initiating agents. Pourable sealer: a type of sealant often supplied in two parts and used at difficult-to-flash penetrations, typically in conjunction with pitch-pockets to form a seal. Prestressed concrete: concrete in which the reinforcing cables, wires or rods are tensioned before there is load on the structural member, holding the concrete in compression for greater strength. Pre-applied sheet membrane: waterproofing materials applied to lagging or a wall prior to the installation of the structural wall (e.g., concrete, shotcrete). Pre-tinning: coating a metal with solder or tin alloy prior to soldering or brazing it. Primary drainage: drainage devices, such as drains or scuppers, which provide for the direct removal of water from a waterproofing system. Primer: (1) a thin, liquid-applied solvent-based bitumen that may be applied to a surface to improve the adhesion of subsequent applications of bitumen; (2) a material that is sometimes used in the process of seaming single-ply membranes to prepare the surfaces and increase the strength (in shear and peel) of the field splice; (3) a thin liquid-applied material that may be applied to the surface of SPVF to improve the adhesion of subsequent application of SPVF protective coatings; (4) a thin, liquid-applied material that may be applied to a surface to improve the adhesion of subsequent applications of waterproofing. Protected membrane roof (PMR): an insulated and ballasted roofing assembly in which the insulation and ballast are applied on top of the membrane (sometimes referred to as an “inverted roof assembly”). Protection course: a separate layer of material installed on top of the membrane to protect a green roof waterproofing membrane from damage. Protection mat: a material used to shield one waterproofing system component from another. Protection slab: a concrete slab, approximately 4 inches (100 mm) thick, placed over a waterproofing membrane to provide a surface for other activity. Psychrometer: an instrument used to measure humidity in the atmosphere from two thermometers that are similar except the

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bulb of one is kept wet and the bulb of the other is dry. Psychrometric chart: chart showing the relationship between dew-point temperature, dry-bulb temperature, wet-bulb temperature and relative humidity. Puncture resistance: the ability of a material to withstand the action of a penetrating or puncturing object. Purlin: horizontal secondary structural member that transfers loads from the primary structural framing. PVC: polyvinyl chloride. R-value: See Thermal resistance. Raggle: a groove or slot, often cut in a masonry wall or other vertical surface for inserting an inset flashing component such as a reglet. Reglet: a sheet-metal receiver for the attachment of counterflashing. A reglet may be surface-mounted, inset into a raggle or embedded behind cladding. Reinforced membrane: a waterproofing membrane that has been strengthened by the addition or incorporation of one or more reinforcing materials, including woven or nonwoven glass fibers, polyester mats or scrims, nylon or polyethylene sheeting. Relative humidity (RH): the ratio of the pressure of water vapor present in a given volume of air to the pressure of fully saturated water vapor at the same temperature, expressed as a percentage. Release tape (or strip): a plastic film or paper strip that is applied to the back of self-sealing shingles and other materials. The strip prevents the material from sticking together in the roll or bundle. With asphalt shingles, the strip need not be removed for application of the shingles. Replacement: the practice of removing an existing waterproofing system down to the deck and replacing it with a new waterproofing system. Reservoir layer: commonly a polyethylene-based panel formed into a three-dimensional array of water-reservoir cups and drainage channels, which store moisture for plant growth. The panels are designed to hold a specific amount of moisture by use of overflow holes that limit the capacity of the cups. Ridge: highest point on the deck, represented by a horizontal line where two deck areas intersect, running the length of the area. Ridging: See Buckle. Roll materials: a general term applied to rolls of waterproofing felt, ply sheet, etc., which are typically furnished in rolls. Roof assembly: an assembly of interacting roof components including the roof deck, vapor retarder (if present), insulation and roof covering. Roof cement: See Asphalt roof cement or Coal tar roof cement. Roof seamer: machine that welds laps of membrane sheets together using heat, solvent or dielectric energy. Roof system: a system of interacting roof components, generally

The NRCA Green Roof Systems Manual—2007 Edition

consisting of a membrane or primary roof covering and roof insulation (not including the roof deck) designed to weatherproof and, sometimes, to improve the building’s thermal resistance. Root barrier: a material that prevents migration of plant roots from damaging the membrane. A root barrier typically is a separate layer of material installed on top of the protection course, but it may be combined with a protection course or drainage course. Rubber: a material that is capable of recovering from large deformations quickly and forcibly. Saddle: a small tapered/sloped structure that helps to channel surface water to drains. Frequently located in a valley. A saddle is often constructed like a small hip roof or pyramid with a diamond-shaped base. (See Cricket.) Sag: undesirable excessive flow in material after application to a surface. Saturated felt: a felt that has been immersed in hot bitumen; the felt adsorbs as much bitumen as it can retain under the processing conditions but remains porous and contains voids. SBS: See Styrene butadiene styrene. Scarfed: shaped by grinding. Screeding: the process of striking off excess concrete to bring the top surface of the concrete to the proper finish and elevation. Scrim: a woven, nonwoven or knitted fabric composed of continuous strands of material used for reinforcing or strengthening membranes. Scupper: drainage device in the form of an outlet through a wall, parapet wall or raised edge lined with a soldered sheet-metal sleeve. SDI: Steel Deck Institute. Sealant: (1) a material that has the adhesive and cohesive properties to form a seal; (2) a mixture of polymers, fillers and pigments used to fill and seal joints where moderate movement is expected; unlike caulking, it cures to a resilient solid. Sealant backing: a compressible material placed in a joint before applying a sealant. Sealer: a coating designed to prevent excessive absorption of finish coats into porous surfaces; a coating designed to prevent bleeding. Sealing washer: a rubber or neoprene washer, sometimes metal-backed, typically placed on a fastener to prevent water from migrating into and through the fastener hole. Seam: a joint formed by mating two separate sections of material. Seams can be made or sealed in a variety of ways, including adhesive bonding, hot-air welding, solvent welding, using adhesive tape or sealant, etc. Seam sample: in single-ply and sometimes modified bitumen membrane roofing, a sample from the membrane that extends through the side lap of adjacent rolls of membrane, taken for the purpose of assessing the quality of the seam.

The NRCA Green Roof Systems Manual—2007 Edition

Secondary drainage: emergency or overflow drainage devices, such as drains or scuppers, which provide for drainage relief from a waterproofing system if primary drains allow water to build up for any reason. Self-adhering membrane: a membrane that can adhere to a substrate and to itself at overlaps without the use of an additional adhesive. The undersurface of a self-adhering membrane is protected by a release paper or film, which prevents the membrane from bonding to itself during shipping and handling. Self-drilling screw: a fastener that taps and drills its own hole during application. Self-tapping screw: a fastener that forms receiving threads when turned in a previously drilled hole. Selvage: (1) an edge or edging that differs from the main part of a fabric, granule-surfaced roll roofing or cap sheet, or other material; (2) a specially defined edge of the material (lined for demarcation), which is designed for some special purpose, such as overlapping or seaming. Semi-intensive (moderate depth) green roof system: green roof system with an engineered soil-based growth medium approximately 6 to 10 inches deep.

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Side lap: the continuous longitudinal overlap of neighboring like materials. Side lap fastener: a fastener used to connect adjacent panels together at the side lap. Siding: the finish covering of an exterior wall of a frame building; the siding may be a cladding material such as wood, aluminum or vinyl (but not masonry). Sieve: an apparatus with square apertures for separating sizes of material. Sill: the bottom horizontal framing member of an opening, such as below a window or door. Sill flashing: a flashing of the bottom horizontal framing member of an opening, such as below a window or door. Single-ply membranes: roofing and waterproofing membranes that are field-applied using just one layer of membrane material (either homogeneous or composite) rather than multiple layers. Single-ply roofing: a roofing system in which the principal roof covering is a single-layer flexible membrane, often thermoset or thermoplastic membrane.

Separator layer: See Slip sheet.

Skinning: the formation of a dense film on the surface of a liquid coating or mastic.

Service temperature limits: the minimum or maximum temperature at which a coating or other material will perform satisfactorily.

Skirt flashing: a formed metal counterflashing secured under a mechanical unit or skylight to cover and protect the upper edge of a base flashing and its associated fasteners.

Set: to convert into a fixed or hardened state by chemical or physical action.

Slab: a layer or reinforced concrete, generally flat and horizontal (or minimally sloped), usually of uniform thickness, placed on prepared earth or supported by beams, columns or walls.

Shading: slight differences in surfacing color, such as shingle granule coloring, that may occur as a result of manufacturing operations. Shark fin: an upward-curled felt side lap or end lap. Shear strength: the resistance to forces that cause or tend to cause two contiguous parts of a body to slide relative to each other in a direction parallel to their contrast. Shelf life: the maximum time a packaged material can be stored under specified conditions and still meet the performance requirements specified. Shingling: the procedure laying parallel felts so that one longitudinal edge of each felt overlaps and the other longitudinal edge underlaps an adjacent felt. Normally felts are shingled on a slope so that water flows over rather than against each lap. Shrinkage: a decrease in one or more dimensions of an object or material. Shrinkage crack: in waterproofing, a separation in a material, such as a concrete substrate, caused by the inability of the material to resist a reduction in size that occurs during its hardening or curing process or both. SI: an abbreviation for the International System of Units (Le Systeme International d’Unites).

Slip sheet: sheet material, such as reinforced kraft paper, rosinsized paper, polyester scrim or polyethylene sheeting, placed between two components of a roof assembly (such as between membrane and insulation or deck) to ensure that no adhesion occurs between them and to prevent possible damage from chemical incompatibility, wearing or abrasion of the membrane. Slope: the angle of incline, usually expressed as a ratio of rise to run, or as an angle. SMACNA: Sheet Metal and Air Conditioning Contractors National Association. Softening point: the temperature at which bitumen becomes soft enough to flow, as determined by an arbitrary, closely defined method (ASTM D36 or D3461). Softening point drift: a change in the softening point of bitumen during storage or application. (See Fallback.) Soil stack: a sanitation pipe that penetrates the waterproofing; used to vent plumbing fixtures. Solder: a lead/tin mixture that is melted and used to bond two pieces of some types of metals together. Solid mopping: See Mopping. Solids content: the percentage by weight of the nonvolatile matter in an adhesive.

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Solvent: any liquid used to dissolve another material. Solvent cleaners: used to clean some single-ply waterproofing membranes prior to splicing, typically including heptane, hexane, white gasoline and unleaded gasoline. Solvent welding: a process in which a liquid solvent is used to chemically weld or join together two or more layers of certain membrane materials (usually thermoplastic). Spalling: breaking off of plate-like pieces from a concrete, rock or masonry surface. Special steep asphalt: asphalt complying with ASTM D312, Type IV. (See Asphalt.) Specification: a precise statement of a set of requirements to be satisfied by a material, product, system or service. Splice: bonding or joining of overlapping materials. (See Seam.) Splice plate: a metal plate placed underneath the joint between two pieces of metal. Splice-tape: cured or uncured synthetic rubber tape used for splicing membrane materials. Split: a membrane tear resulting from tensile stresses. Split slab: a term used to describe two separate concrete slabs. The first is placed as a slab on grade or suspended slab and covered with waterproofing and a drainage system. The second slab, also referred to as a topping slab, is then placed over the underlying slab and waterproofing. (See Between-slab membrane.) Spot mopping: See Mopping. Spread coating: a manufacturing process in which membranes are formed using a liquid compound that is spread onto a supporting reinforcement base layer and then dried to its finished condition. Sprinkle mopping: See Mopping. Spunlaced: a nonwoven fabric made by mechanically bonding a dry-laid staple fabric by water jet, which entangles the individual fibers. Square: a unit used in measuring roof area equivalent to 100 square feet of roof area. Squeegee: (1) a blade of leather or rubber set on a handle and used for spreading, pushing or wiping liquid material on, across or off a surface; (2) to smooth, wipe or treat with a squeegee. Stainless steel: an alloy of steel that contains chromium and also may contain nickel or copper. Generally has good resistance to corrosion. Starter sheets: (1) felt, ply sheet or membrane strips that are made or cut to widths narrower than the standard width of the roll and used to start the shingling pattern at an edge of the roof; (2) particular width sheets designed for perimeters in some mechanically attached and fully adhered single-ply systems. Static load: any load, as on a structure, that does not change in magnitude or position with time.

The NRCA Green Roof Systems Manual—2007 Edition

Steel: a malleable alloy of iron and carbon produced by melting and refining pig iron and/or scrap steel; graded according to the carbon content (in a range from 0.02 percent to 1.7 percent); other elements, such as manganese and silicon, may be included to provide special properties. Steel joist (open web steel joist): normally used as a horizontal supporting member between beams or other structural members, suitable for the support of some roof decks. Steep asphalt: asphalt complying with ASTM D312, Type III. (See Asphalt.) Steep-slope roofs: a category of roofing that generally includes water-shedding types of roof coverings installed on slopes exceeding 3:12 (14 degrees). Stick clip: in waterproofing, a nonpenetrating fastener that is adhered to the waterproofing surface; typically used to retain insulation, drainage panels, prefabricated protection materials, etc., against the waterproofing to prevent sliding and displacement. Stress: the internal resistance of a material to a force, measured as a force per unit area. Strip mopping: See Mopping. Stripping or strip-flashing: membrane flashing strips used for sealing or flashing metal flashing flanges into the waterproofing membrane. Stripping in: application of membrane stripping ply or plies. Styrene butadiene rubber: high-molecular-weight polymers having rubber-like properties; formed by the random copolymerization of styrene and butadiene monomers. Styrene butadiene styrene copolymer (SBS): high-molecularweight polymers that have both thermoset and thermoplastic properties and are formed by the block copolymerization of styrene and butadiene monomers. These polymers are used as the modifying compound in SBS-polymer-modified asphalt roofing membranes to impart rubber-like qualities to the asphalt. Substrate: the surface upon which the waterproofing membrane is applied (e.g., in waterproofing, the structural deck or vertical surface). Sump: an intentional depression around a drain or scupper that promotes drainage. Sump pan: a metal pan used to create a depression around a drain or scupper to enhance drainage. Superimposed loads: loads that are added to existing loads. For example, a large stack of insulation boards placed on top of a structural steel deck. Surface erosion: the wearing away of a surface due to abrasion, dissolution or weathering. Surfacing: the wearing or top layer of a traffic-bearing waterproofing membrane. Surfactant: contraction for “surface active agent,” a material that improves the emulsifying, dispersing, spreading, wetting or other surface-modifying properties of liquids.

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Tack-free time: for waterproofing, a curing phase of a trafficbearing waterproofing membrane to when the material is no longer sticky.

it is necessary to determine the overall thermal performance of a construction, it is appropriate to convert the individual thermal conductance (C) values to thermal resistance (R) values (i.e., R=1/C) and then add the thermal resistance values (i.e., RT=R1 + R2 + … ).

Talc: whitish powder applied at the factory to the surface of some roofing materials (e.g., vulcanized EPDM membranes), used as a release agent to prevent adhesion of the membrane to itself. Taping: (1) the technique of connecting joints between insulation boards or deck panels with tape; (2) the technique of using selfadhering tape-like materials to seam or splice single-ply membranes. Tear resistance: the load required to tear a material, when the stress is concentrated on a small area of the material by the introduction of a prescribed flaw or notch. Expressed in psi (pounds force) per inch width or kN/m (kilonewton per meter width). Tear strength: the maximum force required to tear a specimen. Tensile strength: the strength of a material under tension as distinct from torsion, compression or shear. Termination: the treatment or method of anchoring and/or sealing the free edges of the membrane in a waterproofing system. Terne: an alloy of lead and tin used to coat sheets of carbon steel or stainless steel for use as metal roofing sheet. Terra cotta: low-fired clay either glazed or unglazed. Test cut: a sample of the waterproofing system or assembly that exposes the deck and is used to diagnose the condition of the membrane; evaluate the type and number of plies or number of membranes; or determine rates of application (e.g., the weight of the average interply bitumen moppings). Thermal bridge: the penetration of a material of high thermal conductivity (e.g., a metal insulation or roof membrane fastener) through a material of low thermal conductivity (e.g., thermal insulation); the result is a lowered thermal resistance for the assembly. Thermal cycling: sequence of values caused by a repetitive temperature differential due to changes in radiant energy. Thermal conductance (C): the time rate of heat flow through a unit area of a body induced by a unit temperature difference between bodies. In English (inch•pound) units of measurement, the number of Btu that pass through a specified thickness of a one-square-foot sample of material in one hour with a temperature difference between the two surfaces of 1 degree Farenheit. In English (inch•pound) units, it is expressed as Btu/h•ft2•F. Note 1: A thermal conductance (C) value applies to a specific thickness of a specific material. Note 2: It is mathematically incorrect to multiply or divide the thermal conductance (C) value for a specific thickness of a material to determine the thermal conductance value of a different thickness of the same material. Note 3: It is mathematically incorrect to add thermal conductance (C) values to determine overall thermal performance. If

Thermal conductivity (k): the time rate of heat flow through a unit area of a homogeneous material in a direction perpendicular to isothermal planes induced by a unit temperature gradient is called thermal conductivity (k or k-value). In English (inch•pound) units of measurement, it is the number of Btu that pass through a 1-inch thickness of a 1-square-foot sample of material in one hour with a temperature difference between the two surfaces of 1 degree Farenheit. In English (inch-pound) units, it is expressed as Btu•inch/h•ft2•°F. Note 1: A thermal conductivity (k) value applies to 1-inch thickness of a specific material. Note 2: It is mathematically incorrect to add, multiply or divide the thermal conductivity (k) value of a material to determine the thermal performance value of a different thickness of the same material. If it is necessary to determine the thermal performance of a specific thickness of a material, it is appropriate to convert the thermal conductivity (k) of the material to a thermal resistance (R) value (i.e., R=1/k) and then perform the mathematical calculation. Thermal expansion: the increase in the dimension or volume of a body due to temperature variations. Thermal insulation: a material applied to reduce the flow of heat. Thermal movement: changes in dimension of a material as a result of temperature changes. Thermal resistance (R): under steady conditions, thermal resistance is the mean temperature difference between two defined surfaces of material or construction that induces unit heat flow through a unit area. In English (inch•pound) units, it is expressed as °F•ft2•h/Btu. Note 1: A thermal resistance (R) value applies to a specific thickness of a material or construction. Note 2: The thermal resistance (R) of a material is the reciprocal of the thermal conductance (C) of the same material (i.e., R=1/C). Note 3: Thermal resistance (R) values can be added, subtracted, multiplied and divided by mathematically appropriate methods. Thermal shock: the stress-producing phenomenon resulting from sudden temperature changes in a roof membrane when, for example, a cold rain shower follows brilliant sunshine. Thermal stress: stress introduced by uniform or non-uniform temperature change in a structure or material that is contained against expansion or contraction. Thermal transmittance (U or U-factor): thermal transmittance (U or U-factor) is the time rate of heat flow per unit area under steady conditions from the fluid (e.g., air) on the warm side of a

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barrier to the fluid (e.g., air) on the cold side, per unit temperature difference between the fluids. In English (inch•pound) units, it is expressed as Btu/h•ft2•°F. Note 1: A thermal transmittance (U) value applies to the overall thermal performance of a system (e.g., roof assembly). Note 2: Thermal transmittance (U) is sometimes called the overall coefficient of heat transfer.

The NRCA Green Roof Systems Manual—2007 Edition

TPO: thermoplastic olefin. Traffic bearing: in waterproofing, a membrane formulated to withstand a predetermined amount of pedestrian or vehicular traffic with separate protection and a wear course. U-Value: See Thermal transmittance. UL: Underwriters Laboratories Inc.

Thermography, Infrared: See Infrared thermography.

UL label: an identification label or seal affixed to a roofing product or package with the authorization of Underwriters Laboratories Inc. The presence of the label indicates the product has met certain performance criteria.

Thermoplastic: a material that softens when heated and hardens when cooled. This process can be repeated provided the material is not heated above the point at which decomposition occurs.

Ultraviolet (UV): invisible light radiation, adjacent to the violet end of the visible spectrum, with wavelengths from about 200 nm to 400 nm (nanometres).

Thermoplastic olefin membrane (TPO): a blend of polypropylene and ethylene-propylene polymers. Colorant, flame retardants, UV absorbers and other proprietary substances may be blended with the TPO to achieve the desired physical properties. The membrane may or may not be reinforced.

Underwriters Laboratories Inc. (UL): an organization that tests, rates and classifies roof assemblies for their resistance to fire, impact, leakage, corrosion of metal components and wind uplift.

Note 3: Thermal transmittance (U) is reciprocal of the overall thermal resistance (RT) of a system (i.e., U=1/RT).

Thermoset: a class of polymers that, when cured using heat, chemical, or other means, changes into a substantially infusible and insoluble material. Thinner: (1) a volatile liquid added to an adhesive or coating material to modify the consistency or other properties; (2) a liquid used to clean equipment or other surfaces. Thixotropic: the property of a material that enables it to stiffen in a relatively short time on standing, but upon agitation or manipulation to change to a very soft consistency or to a fluid of high viscosity, the process being completely reversible. Through-wall flashing: a water-resistant membrane or material assembly extending totally through a wall and its cavities and positioned to direct water within the wall to the exterior, usually through weep holes. Tie-in: in waterproofing, the transitional seal used to terminate a waterproofing application at the top or bottom of flashings or by forming a watertight seal with the substrate, membrane or adjacent waterproofing system. T-joint: the condition created by the overlapping intersection of three or four sheets in the membrane. Toggle bolt: a bolt having a nut with pivoted, flanged wings that close against a spring when it is pushed through a hole and open after emerging from the hole; used to fasten objects to a hollow wall or to a wall that is accessible only from one side. Tongue-and-groove planks: one of the oldest types of dimensional structural wood used as decking. The sides are cut with convex and concave grooves so adjacent planks may join in alignment with each other to form a uniform deck. Topping slab/surface: See Wear course. Torch-applied: method used in the installation of polymermodified bitumen membranes characterized by using open-flame propane torch equipment.

Valley: the internal angle formed by the intersection of two sloping waterproofing planes. Vapor migration: the movement of water vapor from a region of high vapor pressure to a region of lower vapor pressure. Vapor pressure: the pressure exerted by a vapor of a solid or liquid when in equilibrium with the liquid or solid. Vapor retarder: layer(s) of material or a laminate used to appreciably reduce the flow of water vapor. Veneer: (1) a single wythe of masonry for facing purposes that may not be structurally connected; (2) any of the thin layers of wood glued together to form plywood. Vent: an opening designed to convey air, heat, water vapor or gas from inside a building or a building component to the atmosphere. Ventilator: an accessory that is designed to allow for the passage of air. Vermiculite: an aggregate used in lightweight insulating concrete, formed by heating and expanding of a micaceous material. Viscosity: the resistance of a material to flow under stress. For bitumen, measured in centipoise. (See Viscous.) Viscous: resistant to flow under stress. Void: an open space or break in consistency. Volatile: a relative term expressing the tendency to form vapor. Volatile organic compounds (VOC): means any compound of carbon, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, and ammonium carbonate, which participate in atmospheric photochemical reactions. Vulcanization: an irreversible process during which a rubber compound, through a change in its chemical structure (for example, cross-linking), becomes less plastic and more resistant to swelling by organic liquids and elastic properties are conferred, improved or extended over a greater range of temperature.

The NRCA Green Roof Systems Manual—2007 Edition

Water cure: a method of curing a material, such as concrete, by applying a fine mist of water over the surface to control the rate of moisture evaporation from the material. Water cutoff: See Cutoff. Water table: the level within the ground below which the soil is saturated with water. Water vapor transmission: a measure of the rate of transmission of water vapor through a material under controlled laboratory conditions of temperature and humidity. Customary units are grains/h•ft2. Waterproof: the characteristic of a membrane, membrane material or other component to prevent water entry. Waterproofing: treatment of a surface or structure to prevent the passage of water under hydrostatic pressure. Waterproofing assembly: an assembly of interacting waterproofing components including the deck, membrane, protection/ drainage/insulation course and overburden. Waterproofing membrane: a continuous layer used as a treatment of a surface or structure to prevent the passage of water under hydrostatic conditions. Waterstop: devices installed at the intersection of cold joints in concrete walls and slabs, walls and footings, or at vertical joints in concrete work as a secondary means of protection against water infiltration. Watertesting: a 24-hour standing- or flowing-water test to evaluate whether a waterproofing system (not a dampproofing system) is leak-free under hydrostatic (standing water) or nonhydrostatic (flowing water) conditions. Wear course: the top layer of surfacing that carries pedestrian or vehicular traffic. Sometimes referred to as wearing surface. Wearing surface: See Wear course. Weatherproof: the ability of a membrane or roof covering to prevent the passage of water with a limited amount of hydrostatic pressure. Weep holes: small openings whose purpose is to permit drainage of water that accumulates inside a building component (e.g., a brick wall, skylight frame, etc.). Weld: to join pieces of metal together by heat fusion. Wet: a condition where free water is present in a substance. Wet bulb temperature: the temperature of air as registered by a thermometer whose bulb is covered by a water-wetted wick. Wet film thickness: the thickness, expressed in mils, of a coating or mastic as applied but not cured. For comparison, see Dry film thickness. Wicking: the process of moisture movement by capillary action. Z section: a member formed in the shape of a “Z” from coiled steel stock.

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Zinc: a hard bluish-white metal, brittle at normal temperatures, very malleable and ductile when heated, not subject to corrosion, used for galvanizing sheet steel and iron in various metal alloys and as an oxide for white paint pigment.

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The NRCA Green Roof Systems Manual—2007 Edition

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