Basement Construction Guide

SITE GUIDE

site guide

Basement waterproofing

Foreword This publication is one of a series related to basements for housing. It has been produced under the direction of the Basement Development Group, which was initiated and is co-sponsored by the British Cement Association.

Acknowledgements The British Cement Association (BCA) is grateful to the British Structural Waterproofing Association (BSWA) for cosponsoring this publication. It is also grateful for the assistance and comments provide by members of the Basement Development Group and to the considerable work of its Waterproofing Task Group in drafting and progressing this publication. Thanks are also extended to all others who provided input to and comments on the preparatory drafts.

Basement Development Group

Waterproofing Task Group

B Aspin (Chairman), House Builders Federation A K Tovey (Secretary), Tecnicom F Atkins, National Housebuilding Council D Burke, Zurich Municipal M Clarke, British Cement Association P Hart, Institute of Building Control D James, Bovis Homes South West A Jones, Stewart Milne Group Limited B Keyworth, Architect R S Reynolds, Institute of Clerks of Works G R Sharpe, Association of Building Engineers P Trotman, Building Research Establishment

A K Tovey (Chairman), Tecnicom S Brown, Sika Limited V Connolly, Renlon Limited M Falla, Booth Engineering Services Limited Z Ginai, Marley Waterproofing Limited P Hewitt, Vandex UK Limited T Holloway, Renlon Limited M Lenaghan, Servicised Limited I J Moffat, Fosroc Expandilte Limited J A M Padley-Smith, Mastic Asphalt Council and Employers Federation Ltd A J Parker, SCL Group Limited M Radford, RIW Limited

Supporting Trade Groups Autoclaved Aerated Concrete Products Association British Structural Waterproofing Association Concrete Block Association Mortar Producers Association Ready-mixed Concrete Bureau

Many construction activities are potentially dangerous, so care is needed at all times. Current legislation requires all persons to consider the effects of their actions or lack of action on the health and safety of themselves and others. Advice on safety legislation may be obtained from any of the area offices of the Health and Safety Executive. 48.059 First published 1994 ISBN 0 7210 1476 3 Price group D © British Cement Association 1994

Published by British Cement Association Century House, Telford Avenue Crowthorne, Berks RG11 6YS Telephone (0344) 762676 Fax (0344) 761214 From April 1995 the code will be (01344)

All advice or information from the British Cement Association is intended for those who will evaluate the significance and limitations of its contents and take responsibility for its use and application. No liability (including that for negligence) for any loss resulting from such advice or information is accepted. Readers should note that all BCA publications are subject to revision from time to time and should therefore ensure that they are in possession of the latest version.

Contents

Introduction

2

Scope

Principles of design and installation

2

G e n e r a l Contract details Site information Construction category Further considerations Basement and site drainage

Application of waterproofing systems DOS and DON’Ts

3

General to all systems Category 1: Bonded sheet membranes Category 2: Cavity drain membranes Category 3: Bentonite clay active membranes Category 4: Liquid-applied membranes Category 5: Mastic asphalt membranes Category 6: Cementitious crystallization active systems Category 7: Proprietary cementitious multi-coat renders, toppings and coatings Geocomposite drainage systems

Glossary

21

References

21

Production: Words & Pages

1

Introduction The benefits of basements, and their viability and costs were examined in a previous report (1) . This indicated that they can be economically introduced onto most sites. In particular, it showed they have clear advantages where the ground is poor and might otherwise be difficult and possibly uneconomic to build on. However, to ensure success, particular attention must be given to the design and construction of the basement and any necessary waterproofing. This publication provides specific guidance on the site application or installation of the various waterproofing systems and comments on other associated construction matters. A companion publication, Basement waterproofing: Design guide (2), gives design information to help the builder or building designer decide which construction technique and waterproofing method offer the best solution, and to help them avoid unsuitable construction.

Scope The details and comments in this publication relate to the categories of structural waterproofing which provide Grade 2 or 3 internal environments, as defined in BS 8102, which are appropriate for residential basements. A Grade 2 environment is for use as workshops, plant rooms and other areas where the performance level permits no water penetration but where higher levels of water vapour would be tolerable and surface condensation may occur. A Grade 3 environment is for ventilated residential and working areas which require a drier environment.

Principles of design and installation General Applying or installing a waterproofing system are specialist tasks that are just as important as choosing and specifying the system. The manufacturer should have been consulted early in the design stage to ensure that the most appropriate system has been selected. The manufacturer will also be able to carry out the installation or to recommend specialist waterproofing contractors familiar with the system to be used. Installation or application should not be left to inexperienced workers. The British Structural Waterproofing Association can provide details of manufacturers of various waterproofing systems and of appropriate specialist waterproofing contractors.

Contract details The specialist waterproofing contractor should examine the contract drawings and waterproofing specifications to ensure the design requirements are completely understood. Since the designer should have consulted with the manufacturer of the waterproofing system during the design, there should be no obvious errors in the contract details. However, the important thing is that the final construction should perform satisfactorily. The specialist waterproofing contractor should therefore establish that the waterproofing concept does enable a continuous barrier to be created - or otherwise

2

adequately protects the structure - and is practicable to install. Unless otherwise agreed with the designer, the materials and installation should be in accordance with the specified details, and all work should be carried out to the same high standards irrespective of the Grade of internal environment. All junctions, service penetrations, dpc/cavity tray junctions and laps in materials should be formed according to the designer’s or manufacturer’s details. The specialist waterproofing contractor should not use alternative waterproofing systems or membranes since they may not be appropriate for the conditions. For example, the system may have been selected to resist not just water but a specific ground chemical. Similarly, any protection boards or screeds should comply with the specifications and be positioned as on the drawings. In essence, no alterations should be made to the specified materials, their relative position and installation sequence, without clearance from the designer or the manufacturer of the waterproofing system.

Site information Before the form of construction and the necessary waterproofing system can be chosen, information must be gathered on soil type, water tables and other relevant factors. This is the designer’s responsibility. The main contractor should find out from the designer what the site conditions are - particularly the likely severity of ground water conditions, and pass this information to the specialist waterproofing contractor. Sometimes, the main contractor may need to lower the water table temporarily or permanently to enable construction and waterproofing to go ahead. Any lowering of the water table will need to be maintained until the loads acting on the basement, from either itself or in combination with the superstructure, are greater than the forces that would be generated by the water pressures as the water table returns to its original level. Although a site survey will have determined the general nature of the site, there may be local variations. Any significant differences should be brought to the attention of the designer as they may create an additional hazard not previously taken into account. Changes from impervious to permeable soils may produce unexpected water channels. Similarly, interception of previous land drains or other elements could increase the amount of water present. Any unexpected chemicals or suspect materials should also be brought to the designer’s attention.

Construction category The structural walls will usually fall into one of the following three construction categories. Type A (tanked protection) structures will often be of masonry construction, although plain or reinforced concrete may be used. The latter may be in-situ or precast. The structure is regarded as having no integral protection against water ingress and so relies on the applied waterproofing system to provide the necessary control. Masonry walls may need a cement rendering or flush pointing to product an acceptable surface for subsequent application of the waterproofing system.

The waterproofing system will, depending on its type, tolerate certain construction cracks or minor defects. Fine hair-line cracks up to 0.3 mm wide in reinforced construction will generally be acceptable. Any larger or unusual cracks should be brought to the designer’s attention to allow for possible remedial action before the waterproofing system is installed or applied. Type B (structurally integral protection) structures will generally be of reinforced or prestressed concrete. Since they are specifically designed to be water-resistant, further waterproofing will be required only where additional control against free water or water vapour is considered necessary. In some instances, the additional protection may be used to safeguard the structure from aggressive chemicals. Again, any noticeable cracking or defect should be brought to the attention of the designer. Type C (drained protection) structures incorporate a drained cavity in the basement. Although defects in the outer leaf will not usually create problems, they may allow more water to enter the cavity. If too much enters, this might overload the cavity drain and lead to water penetrating the basement. The drainage channels must be properly formed and positioned, be free from obstructions, and be approved under test. Any defect or suspect area in the outer leaf should be raised with the designer before the inner cavity drain system is installed. The surface of concrete floors or oversite should be prepared to suit the particular waterproofing system to be used.

Further

considerations

Control of condensation Because window areas are often reduced, there tends to be less natural ventilation in basements than in other parts of the structure. The designer will pay particular attention to this and detail specific heating and ventilation measures. It is important that any ventilation system is properly installed and not obstructed by waterproofing systems inside the structure. The waterproofing system must be installed where indicated by the designer as otherwise there could be excessive interstitial or surface condensation.

System restraint Some waterproofing systems need to be restrained so that they can resist the hydrostatic pressure. The mass and thickness of such restraint must comply with the designer’s or manufacturer’s details.

Chemical barriers An externally applied membrane may have been specified to resist the effects of aggressive chemicals in the soil. It must not be replaced by any other membrane or system without the designer’s approval.

Movement joints The designer is advised to eliminate movement joints in the basement substructure wherever possible. Where they are incorporated, details should have been included in the contract drawings and must be followed exactly. If the specialist waterproofing contractor finds movement joints with no specific waterproofing details, the designer must be asked to provide appropriate details. On no account should a waterproofing system be continued directly across movement joints.

Construction joints Where reinforcement crosses construction joints in reinforced concrete structures, the joints are not movement joints and most waterproofing membranes may be directly placed across them. With Type B construction, these joints will often be provided with a waterstop, either within the concrete or on its surface.

Service penetrations Any service penetration through the basement wall or lower floor slab will need special details. It is important to ensure that service penetrations are correctly formed and sealed in accordance with the specification or manufacturer’s instructions. On no account should penetrations be made or their waterproofing attempted without proper details being followed and agreed with the designer and manufacturer of the waterproofing system.

Basement and site drainage Sometimes, installing a waterproofing system may mean that the area around the basement has to be drained. In any case, it is generally good practice to provide perimeter drains to enable any excess percolating water to run away - for example to the downside of a sloping site or to a lower soakaway. Since such drainage may be an essential part of the waterproofing measures, it is generally advisable to make sure this has been installed before the waterproofing system is applied or installed.

Application of waterproofing systems - DOs and DON’Ts Each waterproofing system has its own characteristics and application methods. In addition, each has procedures which should be adhered to (dos) and aspects which may later lead to defects or problems (don’ts). These are listed by category on the following pages, followed by some dos and don’ts for geocomposite drainage systems.

General to all systems

5 Mastic asphalt membranes

1 Bonded sheet membranes

6 Cementitious crystallization active systems

2 Cavity drain membranes

7 Proprietary cementitious multi-coat renders, toppings and coatings

3 Bentonite clay active membranes 4 Liquid-applied membranes

Geocomposite drainage systems

3

General A: Health & Safety DOs OBTAIN Health & Safety product and equipment data, and have available on site HAVE protective clothing, cleansing creams, etc. on site DISPOSE of release paper, cores, primer tins, etc. properly STORE gas bottles in a compound with high, secure fencing ENSURE adequate ventilation to interior during working (particularly when asphalting) PROVIDE respiratory protection where necessary OBSERVE good housekeeping and general hygiene guidelines KEEP materials out of reach of children

POSSIBLE CONSEQUENCES

DON’Ts DO NOT ignore Health & Safety advice

Accidents - personal injury, prosecution

DO NOT leave waste on site

Third-party injury, prosecution

DO NOT burn scrap

Irritation from smoke and dust

DO NOT transfer materials into unlabelled containers

Improper handling and disposal of unidentifiable materials and risk of injury

DO NOT expose materials to heat or flame

Fire, explosion (primers) and severe personal injury

DO NOT dispose of waste or surplus materials incorrectly

Environmental/legal considerations

B: Information DOs ENSURE that detail drawings, manufacturers’ literature and site instructions are available to operatives on site CHECK that all information and details are in accordance with the waterproofing manufacturer’s instructions SEEK advice and guidance from manufacturer on installation procedures ENSURE specification conforms with the manufacturer’s recommendations CONSULT the manufacturer, if in doubt

POSSIBLE CONSEQUENCES

DON’Ts

4

DO NOT confine information to the site hut

Waterproofing

failure

DO NOT start waterproofing until all the available information has been read and understood

Leakage

DO NOT assume that a manufacturer has been consulted in the design, even where specified. The concept or design may be basically flawed (see Basement waterproofing: Design guide)

Litigation

DO NOT apply membrane without consulting the manufacturer’s literature.

Incorrect application leading to potential failure and financial loss

C: Associated works DOs

ENSURE that associated works are co-ordinated and do not impede or damage waterproofing CHECK that other products and methods are compatible TAKE CARE not to damage system, but repair simple defects according to manufacturer’s instructions ALWAYS refer to manual PROVIDE for attendance of other trades where specified ARRANGE for hoisting facilities and any necessary scaffolding or other plant PROVIDE suitable surface for application ENSURE that measures taken will not interfere with the watertightness of the system

POSSIBLE CONSEQUENCES

DONT’s DO NOT proceed if unsure of next stage or of its effect on work in hand

Damage, leakage, or longer-term adverse reactions between materials

DO NOT drag steelwork across unprotected work

Damage or leakage

DO NOT expect installers to provide services normally provided by other trades

Poor workmanship

DO NOT pierce or breach waterproofing system

Leakage

DO NOT introduce non-specified chemicals, etc.

Harm to waterproofing system

DO NOT introduce any necessary vibration, heat, cold or pressure until the system will accept this

Damage to membrane by imposed loads

DO NOT change drainage details without considering the waterproofing system

Development of water pressures incompatible with forms of construction

DO NOT mix waterproofing systems, even if specified refer to client, designer or manufacturer

Failure through incompatibility of hybrid systems

DO NOT continue if the continuity of the membrane has been broken

Damp/water penetration

5

1 Bonded sheet membranes 1A: Storage and handling DOs STORE as required by the manufacturer RECORD batch numbers to check shelf life STORE upright KEEP in controlled temperature FOLLOW manufacturer’s instructions and check that all ancillary items, tools and protective clothing are present on site

DON’Ts

POSSIBLE CONSEQUENCES

DO NOT leave out on site or allow rolls to become cold or wet

Difficulty in stripping release paper and probably poor adhesion

DO NOT use after shelf life expired

As above

DO NOT store rolls horizontally

Edges of sheet become damaged and rolls become difficult to strip and lay

DO NOT allow material to get too cold

Material could lose its adhesion

DO NOT allow material to get too hot

May become too sticky and prove difficult to lay

DO NOT mix products and ancillary items from different manufacturers

Incompatibility or unsuitability, with no redress in case of failure

1B: Preparation of substrates DOs INSPECT surface to be waterproofed. Does it meet manufacturer’s requirements for finish, imperfections and other criteria? CHECK whether in accordance with drawings, especially provision of chamfers at corners/edges and chases for terminations ENSURE that surface is free from all contaminants (mud, wet, release agents, curing compounds, etc.) and in accordance with manufacturer’s requirements AVOID awkward details ALLOW enough time for curing ALLOW for temporary weather protection in order to provide dry surfaces PLAN works to prevent membrane being left exposed for long period of time

POSSIBLE CONSEQUENCES

DON’Ts

6

DO NOT accept just any degree of finish

Membrane puncture under load

DO NOT waterproof over blow holes, poorly compacted concrete or where brickwork or blockwork has not been flush pointed

Membrane not sandwiched correctly

DO NOT accept surfaces not in accordance with manufacturer’s details (absence of chamfers/chases, etc.)

Leakage

DO NOT dress membrane around an impossible detail

Leakage

DO NOT lay on uncured background

Membrane not bonded to background surface

DO NOT take on the contract unless you are happy the membrane will be protected and that a suitable lap will be left to connect to

Your company will get the blame for foreseen leaks

1 C : Application DOs MAKE SURE the correct primer is applied, following the instructions for number of coats and coverage rate ALLOW primer to dry for the required length of time before applying membrane ENSURE that reinforcing strips, angle fillets, etc. are used at changes in direction and are as required by manufacturer ENSURE that all specified laps are provided and are rolled down ENSURE that all laps are ‘weathered’ FOLLOW manufacturer’s instructions for laying membrane ALWAYS check what is required as a minimum loading coat, since the membrane is designed to be sandwiched

POSSIBLE CONSEQUENCES

DON’Ts DO NOT omit primer on horizontal surfaces unless agreed by manufacturer

Subsequent defects in unbonded sheets provide a path for water ingress

DO NOT ‘stretch’ the primer application

Inadequate bond

DO NOT prime more than can be waterproofed in the same day

Contamination with site dust/condensation/rain resulting in lack of adhesion

DO NOT omit reinforcing strips, etc. at corners to save cost

Leakage

DO NOT omit or skimp on edge or end laps

Leakage paths

DO NOT just unroll and drop down a vertical surface

Air pockets behind the membrane

1 D : Protection and backfilling DOs USE appropriate or specified protection and apply carefully to prevent damage PROP or backfill in sequence when using board protection USE specified backfill material COMPACT in layers as specified ALWAYS USE a suitable protection board, of the correct thickness to avoid damage, spot-bonded to the membrane DISCUSS the backfilling procedure with the site manager or design team. If this work is to be done by others, arrange to be present to check for site damage ENSURE that the backfilling does not impede a lap joint that you may have to work from later

POSSIBLE CONSEQUENCES

DON’Ts DO NOT store materials on unprotected membrane

Leakage from punctured or damaged membrane

DO NOT tip waste material as backfill

Settlement and downward displacement of protection board and membrane

DO NOT backfill without compacting layers as specified

As above

DO NOT apply protection to damaged membrane without first making repairs

Leakage failure

DO NOT leave a sheet membrane unprotected

Subsequent problems, since damage - whether intentional or not - often goes unrecorded

DO NOT drill or puncture surface without checking with the installer

Loss of waterproofing integrity of the membrane and potential for leakage

7

2 Cavity drain membranes 2A: Storage and handling DO STORE as required by the manufacturer

POSSIBLE CONSEQUENCES

DON’Ts DO NOT leave drainage sheets around on site

Damage

DO NOT allow ancillary sealing tapes to become cold or wet

Difficulty stripping release paper and probably poor adhesion

2B: Preparation of substrates DOs CHECK and remedy unacceptable leaks in concrete or masonry substrate before the system is installed CLEAN horizontal substrate and remove all debris CHECK there are no depressions in floor slab which may cause ponding ENSURE slab drains to drainage exits and pump sump

POSSIBLE CONSEQUENCES

DON’Ts DO NOT lay membrane over unswept substrate

Blockages

DO NOT lay cavity former over uneven floor surface

Damage and ponding, leading to leakage

2C: Application and finishing DOs CHECK total integrity of cavity drainage system and inspect membrane for damage before placing screeds or blockwork finishes ENSURE that mesh reinforcement (if required) for floor screeds is supported ERECT walkways to support access and barrows for placing screeds CHECK and clean out all drainage points/channels ENSURE sump pump (where provided) is operational

POSSIBLE CONSEQUENCES

DON’Ts

8

DO NOT shorten recommended overlaps

Water and moisture penetration

DO NOT omit recommended sealing strips and tapes

As above

DO NOT omit sealing washers for mechanical fixings

As above

DO NOT store materials on completed installations or traffic unnecessarily

Puncture of membrane

DO NOT allow fixing through finished floor screeds, or unauthorised channels in the finished loading screed

Cavity membrane will not be loaded correctly

DO NOT allow additional masonry wall ties without sealing washers

Leakage

DO NOT allow membrane and finishes over membrane to be carried out by two different parties

A meaningful guarantee could not be issued by the membrane installer

2 D : Protection and backfilling DOs CHECK integrity of cavity drainage system before proceeding AT WALLS, construct non-loadbearing blockwork wall in front of cavity drainage system AT FLOORS, keep to specified screed thickness, reinforced if required ENSURE that reinforcement mesh is supported and has not damaged cavity drainage system while being positioned

DON’Ts

POSSIBLE CONSEQUENCES

DO NOT proceed until everything has been inspected and any damage repaired

Water penetration at damaged areas

DO NOT use ties unless properly sealed

Water penetration at ties

DO NOT drag reinforcing mesh across cavity drainage system

Damage and perhaps water penetration

9

3 Bentonite clay active membranes 3A: Storage and handling DOs STORE materials off the ground KEEP dry before use USE gloves when handling loose bentonite

POSSIBLE CONSEQUENCES

DON’T

Prehydration and need for replacement

DO NOT place materials in standing water

3B: Preparation of substrates D O MAKE reasonably flat and free from voids

POSSIBLE CONSEQUENCES

DON’T DO NOT leave stones or voids larger than 50 mm

Waterproofing efficiency impaired

3C: Application and finishing DOs REFER to manufacturer’s fixing guide BRUSH standing water from substrate or blinding ALWAYS lap panels PROTECT from heavy steelwork LAY only what can be covered in one day WET the cut surfaces

DON’Ts

10

POSSIBLE CONSEQUENCES

DO NOT lay panels in standing water

Prehydration and replacement needed

DO NOT place panels on unrendered masonry surfaces

Loss of bentonite into voids. Loss of efficiency

DO NOT walk on wet panels

Need for replacement

DO NOT drag heavy objects across panels

Damage - loss of bentonite

DO NOT leave exposed for more than 48 hours

Prehydration and need for replacement

DO NOT lay large areas and leave uncovered

Prehydration and need for replacement

3 D : Protection and backfilling DOs USE hardboard in specific circumstances (but not normally required) USE sand if possible, but nothing larger than 50 mm (MOT Type II is acceptable) ALWAYS compact well

DON’Ts

POSSIBLE CONSEQUENCES

DO NOT use plastic sheeting or prevent water reaching the system

System takes longer to react

DO NOT leave large voids, or forget to compact

Waterproofing efficiency impaired

11

4 Liquid-applied membranes 4A: Storage and handling DOs PROVIDE dry, safe storage away from sources of ignition RECORD batch numbers KEEP in controlled temperature ROTATE stock

POSSIBLE CONSEQUENCES

DON’Ts DO NOT STORE longer than 12 months

Some loss of solvents, causing increase in viscosity

DO NOT USE beyond shelf life without consulting the manufacturer

As above

4B: Preparation of substrates DOs DRY surface to depth of 1-2 mm REMOVE dust, grease, oils and other contaminants ELIMINATE all hollows and voids FLUSH-POINT masonry walls REMOVE sharp edges or high points REMOVE existing floor or masonry paints PROVIDE 20 mm sand/cement fillet in all internal angles FOLLOW manufacturer’s recommendations for surface flatness, keeping it generally within 3-4 mm ALLOW for temporary weather protection in order to provide dry surfaces PLAN works to prevent membrane being left exposed for long periods

DON’Ts

12

POSSIBLE CONSEQUENCES

DO NOT apply to wet surfaces

Membrane will not bond to substrate

DO NOT apply to a dusty or flaking surface

Membrane will not bond to substrate or may not leave the brush

DO NOT apply to open-textured surface

Continuity of membrane will be broken

DO NOT tamp surface heavily

Will cause pooling in low points

4C: Application and finishing DOs PREPARE surface correctly REFER to manufacturer’s recommendations in cold conditions APPLY at published coverage rates APPLY in two coats ALLOW each coat to dry throughout its thickness REINFORCE angles where necessary ALWAYS employ a preferred applicator, who is conversant with the product

POSSIBLE CONSEQUENCES

DON’Ts DO NOT apply when temperature is below 5°C

Surface may frosty, i.e. wet

DO NOT pour onto substrate or apply thickly

Trapped solvent and failure to cure

DO NOT sand membrane

Breaks continuity of membrane

DO NOT screed until cured

Membrane will be absorbed into screed

DO NOT leave exposed to UV light for more than 28 days

Membrane will weather, become thin and brittle

DO NOT apply the material too thinly

Membrane will not function as designed but instead will leak

DO NOT apply a second coat before the first is fully cured

Will damage continuity of first coat and cause solvent entrapment

4 D : Protection and backfilling DOs External protection USE bitumen-impregnated fibre board horizontally USE geotextile drainage board vertically Internally REINFORCE slab or screed horizontally ADD masonry skin with 20 mm cavity filled with sand/cement mortar as work proceeds In all cases ALWAYS allow for suitable protection which should be provided by the company laying the membrane ENSURE protection is firmly fixed according to manufacturer’s recommendations MONITOR the backfilling process to reduce risk of damage

DON’Ts

POSSIBLE CONSEQUENCES

DO NOT lay protection boards loosely

Movement, exposing membrane

DO NOT leave exposed to backfilling or unprotected against following trades

Damage to the membrane

DO NOT leave membrane unsupported internally

Membrane will ‘blow’, leading to failure

13

5 Mastic asphalt membranes 5A: Storage and handling DOs PROVIDE dry, safe storage for primers, gauges, tools, etc. POSITION plant close to point of application PLACE mastic asphalt blocks tidily near to asphalt mixer

POSSIBLE CONSEQUENCES

DON’T DO NOT increase the distance that molten material is carried

Material could cool down and become difficult to lay

5B: Preparation of substrates DOS PROVIDE base to specified levels, tolerances and finish APPLY float finish to horizontal surfaces ENSURE adequate chases PROVIDE correctly prepared vertical surfaces ENSURE all oils, greases and contaminates are removed from all surfaces

POSSIBLE CONSEQUENCES

DON’T DO NOT penetrate horizontal or vertical surfaces with services

Leakage failure around pipes

5C: Application DOs ENSURE all horizontal and vertical work is applied in three coats PIERCE and make good any ‘blows’ while mastic asphalt is still warm ENSURE all succeeding coats follow the preceding coats without delay

DON’Ts

14

POSSIBLE CONSEQUENCES

DO NOT allow temperature of remelt to exceed 230°C for sustained periods

Adverse effect on viscosity of bitumen

DO NOT lay membrane on wet background

Unacceptable increase in ‘blowing’

DO NOT lay successive coats on cold or contaminated preceding coats

Lack of bond and contamination between coats

DO NOT lay on dusty surfaces

Unacceptable increase in ‘blowing’

5 D : Protection and backfilling DOs PROVIDE protective screed to horizontal asphalt work as soon as practicable after laying PROVIDE vertical brickwork protection and concrete loading coat designed to withstand the expected water pressure on internally applied tanking, MAINTAIN sump with pump facility until all loading is complete - if water pressure present

DON’Ts

POSSIBLE CONSEQUENCES

DO NOT backfill externally without protection to the vertical asphalt

Damage to asphalt by other trades, before and during backfilling

DO NOT store materials, reinforcement, etc. on unprotected membrane or allow it to be trafficked

Puncture damage or cracking

15

6 Cementitious crystallization active systems 6A: Storage and handling DOs KEEP products in dry, well ventilated area WEAR suitable protective clothing to prevent contact with skin, eyes, nose, throat, etc. WASH off immediately if bodily contact occurs

POSSIBLE CONSEQUENCES

DON’Ts DO NOT use materials once they have become wet or hardened

Materials will not hydrate fully

DO NOT leave wet materials on the skin

Burns to skin

DO NOT breathe in dust

Burns to throat

6B: Preparation of substrates DOs ENSURE all surface contaminants are removed ENSURE substrate is sound ENSURE there is an adequate key CONTROL suction

POSSIBLE CONSEQUENCES

DON’Ts DO NOT ignore defects in the substrate

Cracking and debonding of the system

DO NOT leave surfaces soft or dusty

As above

6 C : Application DOs ENSURE surface is correctly prepared MIX strictly in accordance with manufacturer’s instructions MAKE sure substrate is saturated, surface dry STOP all leaks before applying

POSSIBLE CONSEQUENCES

DON’Ts

16

DO NOT apply to dry substrates

Cracking and debonding of the system

DO NOT apply to surfaces running with water

As above

DO NOT apply while a dehumidifier is running

Insufficient

hydration

6 D : Protection and backfilling DOs ENSURE system is properly cured USE appropriate protection when backfilling

DON’Ts

POSSIBLE CONSEQUENCES

DO NOT force-dry the system

Cracking and debonding

DO NOT allow point loading in the backfilling

Damage to coating

17

7 Proprietary cementitious multi-coat renders, toppings, and coatings 7A: Storage and handling DOs FOLLOW manufacturer’s shelf life and general storage conditions STORE in sealed original containers, in frost-free conditions WEAR protective clothing, and keep a copy of the manufacturer’s safety sheet handy KEEP out of reach of children, and dispose of waste and surplus correctly RECORD batch numbers of the additive to check shelf life STORE all ancillary materials, cement and sand correctly

POSSIBLE CONSEQUENCES

DON’Ts DO NOT allow prolonged skin or eye contact

Health hazard

DO NOT allow materials to freeze or be subject to extreme heat, or store in an unsuitable environment

Material may become unusable and system ineffective

DO NOT use materials past their shelf life

As above

DO NOT allow materials to become contaminated

Contaminated material, possible failure

7B: Preparation of substrates DOs STOP infiltrations of water or lower the water table before proceeding ENSURE substrate is of sufficient structural quality and soundness WET the substrate before applying any coating REMOVE all surface applications such as plaster and paint ROUGHEN or hack all the surface to produce mechanical key or use surface retarders when placing concrete REMOVE all contamination, dust, etc. IDENTIFY likely problems or defective areas and agree what will be done as regards repair KEEP within prescribed temperature limits during cure ALWAYS use the sand and cement recommended by the manufacturer

POSSIBLE CONSEQUENCES

DON’Ts

18

DO NOT apply materials to a frosted surface, or when temperature is below 5°C

Slow rate of cure and poor surface bond

DO NOT apply to unsuitable contaminated surfaces

As above

DO NOT apply to uncured substrates

Ineffective system, substrate movement or cracking which may reflect through render

DO NOT use beyond shelf life

Mix will be incorrect and the system will not function

DO NOT use old cement or ungraded sand

As above

DO NOT proceed until water infiltration is stopped

Unable to apply system correctly to surface

DO NOT apply to substrate of inferior structural quality and soundness

Cracking and failure of system

DO NOT apply to incorrectly prepared surface

Poor bond of system to substrate

DO NOT apply to thoroughly dry surface

Rapid drying out of material, causing poor surface bond

7 C : Application DOs MIX in accordance with manufacturer’s instructions and use potable water CONSIDER ground conditions, contamination USE correct grading of sand, and seive sand and cement before use, where appropriate FOLLOW manufacturer’s application procedures, and have a copy available for reference FOLLOW instructions for overcoating/waiting times USE suitable joint materials for sealing movement joints CURE correctly CONSULT BBA certificate for further information where required EMPLOY only experienced applicators MONITOR their progress to ensure backgrounds are prepared correctly and that each coat is applied properly DISCUSS whether fixing pockets are required before starting

POSSIBLE CONSEQUENCES

DON’T DO NOT ‘scratch’ the previous coat to form a key. Use a ‘splatter coat’

System failure and inability to apply materials correctly

DO NOT butt-joint coats

System failure and inability to apply materials correctly. Damp/water penetration

DO NOT use soft sand or old cement

System failure and inability to apply materials correctly. If wrong mix is used, the system will leak

DO NOT expose fresh mortars to frost or to temperatures above 30°C

Cracking and water penetration

DO NOT add unspecified materials to the mix

If wrong mix is used, the system will leak

DO NOT use inexperienced staff

System failure and inability to apply materials correctly

DO NOT apply to unsuitable or unprepared backgrounds

System may not be watertight

AVOID fittings fixed mechanically through the system

Continuity of waterproofing may be compromised, leading to water/damp penetration

DO NOT mix materials incorrectly

Poor quality render, system will leak

DO NOT exceed waiting times between coats

Poor bond between coats

DO NOT use unsieved sand or cement

Oversize grains and foreign bodies can cause problems

DO NOT forget to cure correctly

May cause cracking and water penetration

7 D : Protection and backfilling DOs USE suitable coatings where appropriate (consult manufacturer) BOND fixings

DON’Ts

POSSIBLE CONSEQUENCES

DO NOT drill or puncture surface

System failure, letting in water or damp

DO NOT use unsuitable decorative coatings/finishes

Visual deterioration of coating/finish may occur

19

Geocomposite drainage systems A: S t o r a g e a n d h a n d l i n g DO STORE as required by the manufacturer

DON’Ts

POSSIBLE CONSEQUENCES

DO NOT leave unused material around on site

Damage

DO NOT leave exposed to ultraviolet light for long periods

Decomposition of geotextile fabric

B:

Preparation of substrate D O

ENSURE, for horizontal application, substrate is laid to falls

POSSIBLE CONSEQUENCES

DON’T DO NOT allow trafficking before backfill or concrete oversite is placed to horizontal areas

Damage to drainage composite

C: A p p l i c a t i o n a n d f i n i s h i n g DOs USE correct geocomposite type and fixings to suit substrate INSTALL geocomposite with filter fabric to soil face ENSURE that geocomposite filter membrane extends to wrap drainage pipe or links to a fin or other drain ENSURE drainage outlet is to lower side of structure and drains away from building

DON’Ts

POSSIBLE CONSEQUENCES

DO NOT allow use of dimpled drainage core directly against soft waterproofing membranes

Damage to waterproofing

DO NOT allow mechanical fixing against waterproofing membranes

Damage and leakage

DO NOT allow bonding tapes to become cold or wet

Difficulty in stripping release paper or poor adhesion

DO NOT use sharp-footed reinforcement spacers directly on membrane

Damage and leakage

D : Protection and backfilling D O USE approved backfill material and compact in layers as specified

DON’T DO NOT use clay or chalk soil as backfill

2 0

POSSIBLE CONSEQUENCES Clogging

Glossary Air dry

When the surface humidity of a material is equal to that of the ambient surrounding air

Loading coat

A material applied to the waterproofing membrane to enable it to resist hydrostatic pressure

Low-permeability

Resistant to water penetration

Low water table

Where the water table is permanently below the underside of the lowest floor level

Membrane

A material which forms a continuous effective barrier to the passage of water

Moisture

Water in the form of vapour as well as liquid

Perched water table

Where, because of insufficient permeability of a soil, percolating water is held above the underside of the lowest floor level, resulting in hydrostatic pressure

Protection layer

An element used to provide protection to a waterproofing system

Sandwiched waterproofing

Where the waterproofing system is between the two non-tied leaves of the main structure

Vapour check

A continuous vapour-resistant layer

Vapour resistance

The ability of a material to resist vapour penetration

Vapour-resistant

Excludes water and has a high resistance to vapour penetration

Variable water table

Where the water is occasionally above the underside of the lowest floor level

Water

Water in its liquid form

Waterstop

A product or system, placed in-situ, to prevent the passage of water through a discontinuity or joint in site-placed concrete

Waterproof

Impervious to water, not permitting water to penetrate

Waterproofing system

The total method or combination of materials used to create a waterproof protection

Water-resistant

Having a high resistance to water penetration

Water vapour

Water in its gaseous form

C o m b i n e d s y s t e m Two or more waterproofing systems used together Construction joint Joint formed in-situ, for example in concrete, when continuity is not possible Damp

The condition of a material when wetter than air dry

Damp-proof

Impervious to moisture, not permitting moisture to enter

Damp resistance

The ability of a material to exclude moisture

Damp-resistant

Having a high resistance to moisture penetration

Drained cavity

Expansion joint

External waterproofing

A continuous cavity which intercepts and drains away incoming water Joint that permits relative movement caused by expansion and contraction due to changes of temperature or moisture Where the waterproofing system is positioned and placed against the outside face of the main structure

External (reverse) Where the waterproofing is positioned outside the main waterproofing structure but placed against the enabling works Free-draining

Ground through which free water rapidly drains away

High water table

Where the water table is above the underside of the lowest floor level

Hydrostatic head

Water pressure, expressed as an equivalent depth of water

Hydrostatic pressure

The water pressure exerted as a result of a hydrostatic head

Integral protection

Where the structure itself provides the necessary protection to the passage of water

Kicker

Small concrete upstand, cast above floor level to position wall or column formwork for the next lift

Kickerless construction

A mechanical means of retaining formwork in position, eliminating a kicker

References 1. BRITISH CEMENT ASSOCIATION. Options for quality in houses: Basements 1 - benefits, viability and costs. Slough (now Crowthorne), British Cement Association, 1992. 37 pp. (Ref. C/10) 2. BRITISH CEMENT ASSOCIATION. Basement waterproofing: Design guide. Crowthorne, 1994. 20 pp. (Ref. 48.058).

21

BASEMENT WATERPROOFING: SITE GUIDE

BRITISH CEMENT ASSOCIATION PUBLICATION 48.059

British Cement Association

British Structural Waterproofing Association