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NPQS A1-40 Metal Cladding

National Productivity and Quality Specifications (NPQS)

A1-40 Metal Cladding

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1. 1.1 1.2 1.3 1.4 1.5

GENERAL Scope Related Sections Standards Trade Preamble Abbreviations

3 3 3 3 5 6

2. 2.1


7 7

3. 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15

MATERIALS AND COMPONENTS Types of Metal Cladding General Material Requirements Aluminium Stainless Steel Profiled Sheeting Cladding Protective Coatings Structural Steel Supports Fixings and Fasteners Insulation Membranes Gaskets Sealants Fire stopping Prefabricated Metal Cladding Systems Backing wall

14 14 14 14 15 16 17 18 19 19 20 20 20 20 21 21

4. 4.1 4.2 4.3 4.4 4.5

WORKMANSHIP Fabrication and installation methods Fabrication Erection Installation Protection and Cleaning

22 22 22 23 24 24

5. 5.1 5.2 5.3 5.4 5.5 5.6 5.7

VERIFICATION AND SUBMISSION Submissions Maintenance Submissions Warranty Quality Control Plan Submission Samples and Mock-ups Inspection Tests

26 26 27 27 27 27 28 28

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GENERAL Read with the General Requirements section, and all other contract documents.


Scope This section covers the work requirements for the Metal cladding systems installed as facades of buildings. It covers the commonly used Aluminium and Stainless Steel panels. These will generally be used to clad a backing wall which may or may not form a weathertight barrier.


Related Sections Read this work section in conjunction with the relevant requirements of the other work sections including the following:



Sun-screens and Louvres


External Masonry


Metal Roofs

Standards Unless otherwise agreed by the SO, ensure all of the Works comply with the relevant requirements of the Standards and Codes listed below or referenced in the body of the Specification. Alternative Standards and Codes may be proposed for approval by the SO, provided it can be demonstrated that the alternative Standards and Codes comply with the requirements of the standards specified. All Standards and Codes quoted are the current version, unless specific year references are noted. Singapore Standards BCR Singapore Building Control Regulations SS 370 Metal roofing SS CP 89 Code of practice for metal roofing Other Standards BS 1161 Aluminium alloy sections for structural purposes BS 5080 parts Structural fixings in concrete 1&2 BS 5250 Condensation prediction BS 5950 Structural use of steel in buildings BS 6213 Guide to the Selection of Construction Sealants BS 5889 Silicone sealants BS 8118 Structural use of Aluminium BS 6180 Barriers in and about buildings BS 6496 Specification for powder organic coatings for applicationand stoving to aluminium alloy extrusions, sheet and preformed sections BS 6651 Code of practice for protection of structures against lightning BS 7430 Code of practice for earthing BS 8200 Code of practice for for design of non loadbearing external vertical enclosures to buildings BS EN 499 Welding consumables – covered electrodes for manual metal arc welding of non alloy and fine grain steels classification

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BS EN 1011:

Welding – Recommendation for welding of metallic materials.

Part 1

General guidance for arc welding (AMD 13981)

Part 2

Arc welding of ferritic steels

Part 3

Arc welding of stainless steel

Part 4

Arc welding of aluminium and aluminium alloys

Part 5 BS EN 3506-1

Welding of clad steel Mechanical properties of corrosion resistant stainless steel fasteners.

BS 1703

Refuse chutes and hoppers

BS 2901

Fillers and rods for gas shielded arc welding

BS EN 1461

Code of practice for for design of non loadbearing external vertical enclosures to buildings Building construction. Jointing products. Classification and requirements for sealants Hot rolled steel Aluminium and aluminium alloys Stainless steel fasteners

BS EN ISO 11600 BS EN 10025 BS EN 12020 BS EN ISO 3506 parts 1&2 BS EN 287 parts 1&2 BS EN 440, 499, 756, 758, 1600, 12072 BS 7475 BS EN 288 BS 8000 part 2 CP3, BS 6399 parts 1,2&3 BS EN 10029 BS EN 10048 BS EN 10088 BS EN 10258 BS EN 10259 BS EN 10021 BS 1449 part 1 BS EN 12540 BS EN ISO 1461 BS EN ISO9001 PD 6484 BS EN ISO 12944 pts 1-8

Testing of welders Welding consumables

Welding stainless steel Welding procedures and testing Workmanship on building sites Loading for buildings Stainless steel Stainless steel Stainless Steel Cold-rolled stainless steel and narrow strip and cut lengths – tolerances on dimensions and shape Cold-rolled stainless steel wide strip and plate/steel – tolerances on dimensions and shape General technical delivery requirements for steel and iron products Steel plate sheet and strip Corrosion protection of metals – electrodeposited coatings Specification for hot dip galvanising coating on iron and steel articles Quality assurance systems Bimetallic corrosion Corrosion protection

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CIBSE handbook CIBSE handbook

Condensation prediction

CWCT AAMA 2605.2

Ventilated rainscreen walls Voluntary specification, performance requirements and test procedures for superior performing organic coatings on aluminium extrusions and panels Metal finishing- Thermoset powder coating for architectural applications of aluminium and aluminium alloys

Thermal performance

AS 3715


Trade Preamble 1.4.1

Contractor’s Submissions and Proposals

The design intent including type and locations of the metal cladding systems for the project are indicated in the drawings and schedules. Base on the information supplied, engage qualified and experienced personnel to carry out and submit the following items for the SO’s acceptance: a. Develop all necessary details for the fabrication and installation of the cladding system(s), and to meet with the performance requirements as set out in clause 2.0 below. Details to develop may include shape and sizing of components, structural support, accessories, joints, waterproofing and connections to the building etc. b. Propose manufacturers and products for components of the metal cladding systems when called for. c. Propose method of fabrication, erection/installation. d. Propose details of weather/waterproofing.


Shop Drawings

Produce shop drawings to enable the fabrication and installation of the cladding system. 1.4.3

Co-ordination with other Works

Co-ordinate the metal cladding works particularly the interfacing with the following trades: a. Structural frames b. Walls and masonry c. Windows and doors


Spare Materials

Deliver to site in strong protective packages marked for identification, and store where directed, components and materials for future replacement and repair. Refer to PSD for list.

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Submission to Authorities

Engage a PE (Civil) to carry out the design of the structural supports for the cladding system and submit for BCA approval as a QP for this design. 1.4.6


Provide a ten-year warranty in accordance with contract conditions for the entire cladding system including all components and accessories for the specified performance. 1.4.7

Maintenance Manual

Refer to the PSD for any requirement to provide a maintenance manual. 1.4.8

Quality Control Plan

Refer to the PSD for any requirement to provide a quality control plan. 1.5

Abbreviations a.


Building maintenance unit

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Contractor’s Brief When carrying out the proposals as set out in clause 1.4.1, take account of the following requirements: The performance requirements apply to the complete wall assembly consisting of panels, support frames and backing walls. 2.1.1

Resistance to Loading

Loading general

Withstand loading from inside and outside the building determined in accordance with CP3 using a basic wind speed V=35m/s and terrain appropriate for the location. Transmit all the design loads to the building structure via the anchors as designed with an adequate margin of safety appropriate to each material and product

Gravity loading

Support the self weight of the metal cladding and transmit this weight safely back to the supporting structure without overstressing or permanently deforming any components

Wind loading

Support the design dynamic pressure and transmit these loads safely back to the supporting structure without overstressing or permanently deforming any of components. Account shall be taken of all applicable local pressure coefficients. Sustain no permanent damage to panels, framing members or anchors when tested at both positive and negative applications of the design wind loads multiplied by a factor of 1.5. Framing members shall not be buckled. Panels, beads and capping pieces shall remain securely held and gaskets shall not be displaced. Permanent deformation to framing members shall not exceed 1/500 of the span measured between points of attachment to the structure after loading.

Determination of design pressure

Determine cladding design pressures and other loadings to be used in the design of metal cladding in accordance with procedures established in agreed Codes and Standards. Submit cladding design pressures to the SO for review.

Impact loading

Satisfy the requirements of Tables 3 and 4 of BS 8200 "Design of non-loadbearing vertical enclosures" for category B in table 2. The maximum visually acceptable dent in the metal surface is 10mm in diameter and 3mm in depth.

Maintenance loading

Sustain and safely transmit a static load of 500 N applied horizontally through a square of 100 mm side on any framing in vertical or near vertical metal cladding. Sustain and safely transmit a loading of 0.25kN/m² or 0.75kN applied to all canopies and sunshades with a dimension greater than 600mm.

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Sustain and safely transmit loads at BMU restraint points as advised by BMU manufacturer (or a default value of 3.5kN) in any direction.

Barrier loading

Where the metal cladding or its sub-frame provides protection to a fall, sustain and safely transmit safely each of the following static horizontal loads acting separately: 0.75 kN/m for all occupied spaces acting in all directions at a height of 1.0 m above finished floor level, A uniformly distributed load of 1.0 kN/m² and a point load of 0.5kN acting on any part, up to and including 1.0 m above finished floor level. Sustain and safely transmit crowd loading if requirement confirmed by SO.

Loading from temporary conditions

Sustain and safely transmit any temporary loading that may arise from lifting, storing, transporting, hoisting and installing metal cladding or other Works that may affect the metal cladding.

Combinations of loading

Sustain and safely transmit combinations of loads determined in accordance with the procedures set out in B(C)R.

Metal cladding framing deflection limits for serviceability under load

Determine the positive and negative design loads in all directions from the most onerous combination of loads. Achieve serviceability deflection limits under the combined design loads not exceeding 1/200 of the span of the member measured between points of attachment to the building, or 20 mm, whichever is the lesser. All framing members are to recover fully from the above deflections when the loads are removed. Horizontal panels – dead load deflections to be less than L/180. 2.1.2

Structural design of metal cladding

Design codes

Design metal cladding in accordance with the following codes and standards: a. BS 8118 Aluminium b. BS 8200 Design of non-loadbearing vertical enclosures" c. BS 5950 Steelwork Undertake the design to achieve the performance requirements with appropriate factors of safety as required for the materials and components used. Submit calculations to the S.O. for review Submit calculations endorsed by a PE for onward statutory submission.

Fixing, Anchor and Bracket Design

Take account of any reduction in safe working loads in fixings due to their spacing, location in areas of tension, near edges or proximity to cast in inserts/existing fixings, or thickness of shims.

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Design anchors and their connection to the building structure in order to resist loading. Take account of structural and metal cladding tolerances to determine loading and eccentricity. Identify requirements for any cast in anchors and pass this information to the concrete contractor for incorporation in structure.

Cast-in anchor design

Design cast-in anchors and their connection to the building structure in order to resist loading. Take account of tolerances in structure and metal cladding to determine loading and eccentricity Provide calculations verifying that cast in inserts will resist the loading as follows: No permanent deformation of the insert at 1.5 times design load No failure of the insert at 2 times the design load No failure of structural concrete at 3 times the design working load Identify locations of cast in anchors and pass this information to the concrete contractor for incorporation in structure.

Components subject to the full wind load

Design the air seal and all components external to this to resist the full cladding design pressure.

Vibration and repetitive loading

Resist working loose of anchors and other components due to the effects of vibrations, or cyclic effects of load, deflections and thermal expansion.

Locked in stresses

Avoid the introduction of locked-in stresses that may be detrimental to the performance of the metal cladding. 2.1.3

Resistance to climatic and environmental conditions

Weather resistance

The cladding in combination with any backing wall will prevent leakage of water into the interior of the building from the outer face of the assembly, resulting from wind pressure kinetic energy, gravity, surface tension, or capillary action with any combination of wind and precipitation likely to be experienced, up to and including 600 Pa static pressure for any period of 5 minutes, and 900 Pa dynamic pressure, for 3 second periods at random intervals. Prevent water entering into those parts of the metal cladding that would be adversely affected by the presence of water. Limit air infiltration through the metal cladding to not more than 1.5 cu m/hr per square metre cladding There shall be no region of concentrated airflow through the cladding system or at any interfaces. Maintain weathertightness under reasonably anticipated imposed loads and thermal, structural or other movements.

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Thermal performance and solar gain

Achieve a U-value for the complete wall assembly including metal cladding of 1.1W/m²/°C or better. Achieve at least the performance levels as indicated in the PSD.

Condensation performance

Resist the formation of condensation on visible surfaces, interstices or locations where it is unable to drain.

Design for thermal and condensation performance

Use insulation of appropriate performance to provide adequate level of performance without localised cold bridging where insulation must be locally reduced in thickness such as anchor positions Use vapour barriers as necessary to eliminate condensation around the metal cladding. Assess the heat transferred through metal cladding by 2-dimensional numerical analysis. Use software validated against benchmarks. Summarise the results of the assessment as thermal transmittance (U-values) for the central and perimeter zone of each relevant cladding type. Calculate overall U values for each relevant cladding type as a weighted average of constituent areas, with the weighting method defined. Take into account the internal and external surface heat transfer resistances. Quote these resistances and the parameters that affect them. Take into account the effects of any air spaces, porous materials, and the thermal interaction between elements of the facade.

Climatic Data

Assume: Ambient temperature range Radiant temperature range Relative humidity range Environment

16°C to 40°C 16°C to 80°C 90%±10% Coastal

Gather any additional climatic data required from the Singapore Meteorological Observatory. Submit for review to the SO any additional assumptions concerning temperatures, humidity levels, etc. 2.1.4

Building Movements and Structural Tolerance

Structural Movement and Movement Between Works by Others

Accommodate the following movements in combination; without any reduction in the specified performance, refer to the SO for further guidance and data for calculation input: a. Deflections and movements of the structure and building wall under design loads. b. Changes in dimension and shape of building elements arising from building movements, including settlement, shrinkage, elastic shortening, floor beam

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deflections, creep, wind sway, twisting and racking and thermal and moisture movement. c. Changes due to movement of any joint in the supporting structure or building frame. d. Deflection of framing members under design dead loads and live loads. Incorporate these calculations in the design. e. Thermal and moisture-induced movements of the metal cladding. Incorporate these in the design based on maximum range of temperature and humidity. Propose nominal, minimum and maximum joint widths accounting for tolerances and movements for the SO’s acceptance. Refer to the PSD for design movements and deflections to account for.

Structural Tolerances

Accommodate construction tolerances on structure and back up walls as indicated in the PSD.


Fire and smoke performance

Non-combustible materials

Do not use materials in the metal cladding that readily support combustion or add significantly to the fire load or give off toxic fumes.

Surface spread of flame and fire propagation

Achieve Class O classification when tested in accordance with BS 476: Parts 6 & 7 internally and externally.

Fire and smoke stopping

The complete perimeter wall construction shall prevent the passage of smoke from floor to floor by the insertion of a smoke stop at each floor level in accordance with the requirements of the BCA. The design of the smoke stop is to be approved by the SO. 2.1.6

Acoustic and noise performance

Acoustic performance

Achieve the following STL values against noise break-in: Frequency (Hz)







STL (dB)







Achieve resistance to flanking and floor to floor sound transmission of STC40 unless indicated otherwise in clause 3.1.


Eliminate drumming, creaking, rattling, whistling and any other noises from the metal cladding audible to occupants. Where noted in clause 3.1, use anti-drum backing applied to rear face of metal cladding panels to absorb rain impact noise.

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Achieve the mandatory geometry presented on the Architect’s drawings. Achieve colours and appearances presented on the Architect’s drawings. Achieve an appearance of visually flat panels. No ‘oil-canning’ or visual distortion. No grinning through of stiffeners.

Maintenance and replacement

Design metal cladding to permit removal and replacement of individual assemblies without affecting adjacent assemblies or supporting framework.


Design and install so that drainage of rainwater is predominantly at the outer face. Provide internal drainage within all framing members in order to provide continuous and sequential secondary drainage of any water passing the outermost seals under gravity. Provide means for drainage from all items in the cavity to prevent collection of water or to direct water further inwards. Provide drainage to the outside for all internal cavities. Maximum vertical spacing between flashings to be 12m. Provide continuity at watertightness within internal gutters at all splices between framing members and changes of direction, whilst at the same time allowing for movements concentrated at these positions due to thermal expansions and contractions Ensure continuity of weathertightness to adjacent roof waterproofing finishes and upstands. Ensure disposal of rainwater from metal cladding into rainwater disposal system by providing gutters where necessary to prevent run off over pavements. Ensure no ponding occurs on horizontal surfaces.

Security performance

Resist wilful dismantling in order to gain unauthorised entry or vandalism.


Resist attack or infestation by micro-organisms, fungi, insects, reptiles, birds or bats and rodents. 2.1.8


The system shall be designed to maximise prefabrication. Factory finished elements to be erected directly with minimal site works. Elements of the sub-frame shall be prefabricated and no site welding or tack welding to be permitted, unless incorporated into the design and clearly identified on submission drawings.

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Lightning protection

Meet or exceed the requirements of SS CP 33. Co-ordinate as necessary between the metal cladding and the main lightning protection systems for the building and shall propose appropriate connection points. No external tapes will be accepted. Design the cladding system as a whole to be electrically continuous to earth. 2.1.10

Design for Durability

Do not use carbon steel in locations subject to wetting or condensation or where this will result in corrosion; shortening their design life or compromising safety, however long-term; or, causing rust staining; or, establishing a bimetallic cell with other metals or carbon.

Identify materials and components which under normal service conditions cannot meet the specified design life and design to allow their monitoring and replacement

Identify any recommendations for attic stock.

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Types of Metal Cladding Refer to the PSD for the types of cladding and component requirement for this project.


General Material Requirements 3.2.1

Volatiles in Materials and Components

All materials and components shall be free from volatile components that may migrate with time, or evaporate and re-condense onto other components. 3.2.2


Materials shall be selected, designed and installed to prevent bimetallic corrosion. All materials shall be compatible with the other materials around it within its range of influence for the service life of the metal cladding. 3.3

Aluminium 3.3.1


Designation 6063, temper T6 of BS 1474 unless otherwise agreed with SO Comply with BS EN 486, BS EN 573-3 and BS 1161. Minimum wall thickness in structural parts of 2.5mm. Platforms, webs, flanges, races and screw flutes of sufficient size to satisfy all structural requirements and eliminate distortion of elements in the metal cladding. 3.3.2

Sheet, strip and plate

Not less than 3mm for panels. Not less than 3mm thick for other components exposed to view or to impact. Not less than 1.6mm thick for hidden flashings. Alloy 5005 H24 as appropriate. Isolate all components in direct contact with, but not totally encased in, cementitious surfaces with thin dense PVC or EPDM isolation packs. The use of bituminous paint shall not be accepted. 3.3.3

Composite aluminium panels

Composite aluminium panels shall be: a. Not less than 4mm thick overall. b. Two skins of 0.6mm aluminium sandwiching a solid core of fire retardant thermoplastic material. c. Formed in a continuous thermal bonding process (i.e. are cores not glued to skins with adhesive). d. No voids or debonds in core material.

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All internal and external corners are to be ‘V’-cut and folded with an aluminiumreinforcing angle bonded internally. Minimum bond strength (ASTM D-1781-76) Allowable bending strength Coefficient of expansion (ASTM E228) Tensile yield stress (ASTM D-638-82a)


178 Nm/m 79N/mm² 2.36x10-5 mm/mm/°C 44N/mm²

Aluminium Finishes

Concealed aluminium in wetted areas to be anodised. Applicator is to be approved by the coating manufacturer. Apply PVF2 coating to exposed aluminium in accordance with the coating manufacturer’s instructions. 3.4

Stainless Steel 3.4.1

Stainless steel components

Stainless steel components shall be austenitic, complying with BS En 10088 grades: X2CrNi18-10 (formerly 304 S11) for concealed locations only. X8CrNi18-9 (formerly 304 S31) for concealed locations only. X2CrNiMo17-12-2 (formerly 316 S11) for exposed locations only. X2CrNiMo18-14-3 (formerly 316 S13) for exposed locations only. 3.4.2

Plate, Sheet and Strip

Stainless steel in plate, sheet and strip to comply with BS EN 10029, BS EN 10048, BS EN 10258, BS EN 10259 and BS EN 10088 as appropriate.

Unless noted otherwise, grade 1.44xx (formerly 316) shall be used for visible components, in all other circumstances grade 1.34xx (formerly 304) shall be used.



1G/2G (3A) Ground: Coarse, unidirectional texture; low reflectivity. 1J/2J (3B or 4) Brushed or dull polished: Unidirectional texture; smoother than 1G/2G; low reflectivity. 1K/2K (5) Satin polished: Smoother than 1J/2J. Suitable for marine and external architectural applications. 1P/2P (7 or 8) Bright buffed/polished: Nondirectional finish with high degree of reflectivity. Achieved by mechanical polishing. Note the references in brackets are the nearest equivalent finishes to the superseded BS 1449-2. The finish is achieved on the exposed surface only unless specified otherwise.

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Welding of Stainless Steel

Comply with BS EN 12356 and BS 2901: Part 2: 1990. Use electrical fusion metal-arc method. Carbon-arc or gas welding will not permitted. Undertake in a thorough manner, with edging rod of same composition as sheets or part welded. Weld completed welds, strong and ductile, with excess metal ground off and joints finish smooth to match adjoining surface. Welds shall be free of Mechanical imperfections such as gas holes, pits, runs, crack etc. and shall have same colour as adjoining surfaces. All sheets shall be continuously butted welded together with welds ground smooth and polished. Butt welds made by spot welding strips under beams and filling in the voids with solder and finishing by grinding will not be acceptable Wherever welds occur on surfaces not finished by grinding and polishing, such welds and the accompanying discolouration shall be suitably coated in the factory by means of metallic base paint to prevent the possibility of progressive corrosion to such joints. 3.4.5

Fixtures and Fastenings

Fixings and fasteners shall comply with BS EN ISO 3506-1 and BS EN ISO 3506-2. Unless noted otherwise, grade A4 shall be used for visible fasteners, in all other circumstances grade A2 shall be used. Propose suitable fastener property class for the SO’s acceptance to meet the performance criteria specified. 3.5

Profiled Sheeting


The materials of metal sheeting shall comply with SS 370 and SS CP 89, with the following metallic coating: Zinc aluminium alloy coating Aluminium coating Zinc coating (Galvanised)

Minimum Base Thickness

The MBT of metal roof sheets shall comply with SS CP 89 (2001).

Coating System

Comply with SS 370 and SS CP 89. The following common types of coatings are acceptable: a. PVF2 b. XPD c. XPD Pearlescent Steel d. Polyester e. XRW f.

XRW Ultra

Other types of coatings may be acceptable subject to the SO’s agreement.

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Cladding Protective Coatings 3.6.1


Apply coats after completion of fabrication and drilling of all fixing holes. Remove all burrs and sharp amses prior to coating. 3.6.2


Galvanizing shall be to BS EN ISO 1461. Provide all necessary vent and drain holes in approved locations and seal to approval after galvanizing. 3.6.3

Electrolytically Zinc Coating

Electrolytically zinc coated cold rolled steel flat products such as ‘zintec’ shall be to BS EN 10152. 3.6.4

Cadmium/Zinc Plating

Cadmium/zinc plating of steel to BS 1703. 3.6.5

Chromium Plating

Chromium plating shall be to BS 1224. 3.6.6

Vitreous Enamelling

Vitreous enamelling to steel surfaces shall be to BS 3830. 3.6.7


Anodizing to aluminium surfaces shall be to BS 3987 for external applications and to BS 1615 to general internal applications. 3.6.8

Externally Painted Steel

Refer to section A1-80-3 “External Painting and Coating” clause 3.1. 3.6.9


Comply with AS1231 thickness grade 25. 3.6.10


Wet applied fluoropolymer to comply with AAMA 2605-2 1998. Resin content minimum of 70%, minimum coating 25 microns. Coating shall be supplied by a single applicator. PVF2 coating shall (be / have) a. Dense and consistent b. Minimum cured coating thickness 25 microns. c. Fully cured d. No seeding

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e. Free from flow lines, streaks, pin holes, blisters, ‘orange peel’, tears, damage, contamination, inclusions and other defects and surface imperfections when viewed from a distance of 1meter under normal diffused daylight. f.

Neither be significantly thicker or thinner than adjacent areas nor be split at changes of angle.

g. No exposed areas of uncoated metal.


Polyester Powder Coating

Comply with AS3715. Minimum thickness 50 microns. Propose suitable thickness for the SO’s acceptance. 3.7

Structural Steel Supports 3.7.1

Carbon Steel Components

Refer to structural specifications for requirements relating to secondary steel framing. The use of carbon steel shall only be permitted where the component is readily accessible for regular inspection and maintenance. Where used, it shall be one of the following: a. Hot rolled steel complying with the requirements of BS EN 10025. b. Hot rolled sections to BS 4: Part 1, BS EN 10210-2 and BS EN 10021-1, tubes to BS 6323: Parts 1, 2 & 3 and angles to BS 4848: Part 4. c. Cold formed pre-galvanised steel sections to BS EN 10142, BS EN 10143, BS EN 10147 d. Steel sheet to BS 1449: Part 1.


Steelwork Corrosion Protection

For general requirements refer to structural specifications.

Hot Dip Galvanising

Hot dip galvanise all carbon steel components after forming and drilling in accordance with BS EN 1461 for items less than 5mm thick and BS 5493 for items more than 5mm thick. Isolate all galvanised steel components in direct contact with, but not totally encased in, cementitious surfaces with thin dense PVC or EPDM isolation packs. The use of bituminous paint shall not be accepted.

Paint Finishes

Refer to structural specifications. Colours and gloss levels of any exposed items to the SO’s direction. Finished surfaces shall be: a. Dense and consistent b. Free from flow lines, streaks, pin holes, blisters, tears, lumps and other coating defects or surface imperfections when viewed from a distance of 1 metre under normal diffused daylight.

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Fixings and Fasteners 3.8.1


Stainless steel

Use stainless steel fixings and fasteners with stainless steel and aluminium, or with non-metallic components wherever wetting may occur. Stainless steel fasteners may have hardened tips of other composition for self-drill and self-tap screws only. Use grade A4 to BS 6105 where visible, may be reduced to grade A2 to BS 6105 where not visible.

Carbon steel bolts with carbon steel components

Ordinary bolts and nuts to BS EN 24032, BS EN 24033, BS EN 24034. All plain and tapered washers to BS 4320, Form E. Nuts to BS 4190 for grade 8.8. The use of zinc plating to BS 1706 – Fe/Zn 8 is acceptable where serrated fixings are used. 3.8.2

Cast-in Anchors

Use Cast in anchors unless otherwise agreed with SO, Post-fixed anchors will not normally be accepted. Where used, post-fixed anchors shall be stainless steel or sheridised / galvanised mild steel. 3.8.3


Use stainless steel or aluminium brackets and stainless steel fixings wherever wetting may occur (including condensation) Brackets shall (have / be): a. Resist all loads, movements and dimensional changes that may occur in the building due to thermal changes, deflections, settlement and creep. b. Resist all loads, movements and dimensional changes that may occur to the metal cladding. c. Allow for construction tolerance in the all components and structure. d. Adjust by small increments in and out, up and down and side to side e. Use lock nuts to prevent loosening due to movements and/or vibrations. f.

State the torque values for tightening all bolts on the Contractor's drawings

g. State the maximum allowable shim dimension on the Contractor's drawings and verify the capacity of the bolt by calculation for this case. Shimming shall not be greater than 10mm. h. Shims shall be of the same metal as the bracket.


Insulation Thermal insulation, where included, shall (be / have):

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a. Inert, durable, rot and vermin proof, CFC and HCFC free. b. Not support mould fungal or bacteria growth. c. Maintain the specified performance throughout the service life of the metal cladding. Allow for reduced performance of insulation due to the effects of moisture and ageing. 3.10

Membranes Membranes within the metal cladding shall (be / have): a. Butyl or EPDM b. Mechanically fixed c. Formed into shapes compatible with the building interfaces d. Achieve necessary continuity by vulcanising the seams. e. Seal all joints and penetrations. f.

UV resistant

g. The necessary tensile strength and elasticity for their application h. Water vapour permeability appropriate for their application.


Gaskets All gaskets shall (be / have): a. Extruded EPDM complying with the provisions of BS 4255. b. Cellular profiled gaskets shall comply with ASTM C509.


Sealants Select and install in accordance with BS 6213. Use in accordance with the manufacturer’s directions, particularly relating to the use of primers. Sealants shall (be / have): a. Non-gassing polyethylene closed cell foam backing rods b. Primers and joint preparation materials as recommended by the sealant manufacturer. Silicone sealants shall comply with BS 5889. Refer colour selection of any visibly exposed sealants to the SO.


Fire stopping Fire stops shall be based upon mineral fibre of appropriate density, held captive by metal trays mechanically fixed to the underside of the slab and allowing for movement.

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NPQS A1-40 Metal Cladding


Prefabricated Metal Cladding Systems Where indicated in the drawings or clause 3.1, propose prefabricated metal cladding systems for SO’s acceptance. Metal cladding systems shall (be / have): a. Drainage system for any water passing the outermost panels or condensing within the cavity to drain to the outside b. Internal air seal and vapour barrier c. Replacement without the need to dismantle the primary framing members d. Stainless steel pins where panels hook onto pins e. Horizontal and vertical cavity zoning


Backing wall Back up walls may be in situ concrete, blockwork, brickwork, steel stud and panelling. Where noted in clause 3.1, design and install back up wall to achieve airflow not more than 1.5 cu m/hr/m² at 600 Pa. There shall be no region of concentrated airflow through the background wall or at any interfaces. The backing wall is to withstand the full design wind pressure. Do not attach framing members, rails or fixings to non-structural back up walls unless the wall has been designed to carry these loads. Compartment the cavity between metal cladding panel and back up wall. Ensure that all flashings, fixings and other items within cavities shed water outwards. The wall shall incorporate appropriate water barrier appropriate to resist and control the expected water passing the cladding. Water barriers may include as a single layer or in combination render, membranes, water resistant coatings, etc.

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Fabrication and installation methods Submit method statements describing how it is proposed to fabricate and install the Works to the SO for review: Select methods used for fabrication and installation that will achieve the specified performance. Use jigs computer controlled tools and laser setting out equipment wherever appropriate to achieve accuracy. Use the correct tools for each task and equipment that is well maintained. Do not use blunt and worn tools. Carry out grinding, cutting, shaping and finishing materials using tools, techniques and ancillary materials that will not contaminate metal cladding components with particles or substances which could disfigure, stain or corrode them. Undertake the assembly of components under factory controlled conditions Do not Site weld.


Fabrication 4.2.1

Fabrication and installation marking

Mark components and materials clearly wherever this is required in order to identify strong points for lifting, permit assembly or installation in a particular sequence; or interlocks occur; or confusion could foreseeably arise between upper and lower faces, left and right handed pieces, top and bottom, or lengths close but critically different from one another. Mark in such a way as not to affect the performance of the Metal cladding with removable or marks that will be concealed when installed. 4.2.2

Fabrication of metal components

Metals should be mechanically cut and drilled wherever possible. Cut surfaces shall be true to line and level and free from burrs. The cut sections that form the contact surfaces of any joint shall be free of irregularities and unevenness and dressed for welding as necessary. No site cut edges shall be visible in the finished Works. 4.2.3

Factory Sealant Work

Apply and cure sealants in accordance with their manufacturer’s directions on minimum and maximum temperature and RH conditions. Achieve the depth to width geometry. Prevent three-sided adhesion. Use appropriate backer rods, tapes, surface preparation and primers as manufacturer’s directions. Tool off sealants neatly Use small joint sealant in crevices where extrusions mitre together.

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Fabrication tolerances

Metal cladding framework

Achieve the following maximum allowable tolerances for all metal cladding framework: a. ±1.5 mm on length b. ±1.5 mm on straightness c. ±2° accuracy on angles d. ±1mm on sides and ±2mm on diagonals of opening positions

Metal cladding panels

Achieve the following maximum allowable tolerances for individual panels a. ±2.0 mm on height and width b. ±1.0 mm on straightness of edges c. ± 2.0mm on flatness of panels including both panel warping and surface distortion


Erection 4.3.1

Line and level survey

Undertake a survey of line and level and condition of structure and openings to verify acceptability to receive metal cladding. 4.3.2

Site setting out marks

Use removable marking or place marks in locations where they will be concealed in the Metal cladding when installed. 4.3.3

Handling of materials and components

Handle metal cladding by designed strong points only. 4.3.4

Erection Tolerances

Install the metal cladding to the more onerous of the following permitted deviations: Horizontal and vertical position on elevation from site datum Line Level: Plumb: Plane: Intersection:

± 10 mm. ± 2 mm in any one storey height, or structural bay width. ± 2 mm in any one structural bay. ± 2 mm in any one-storey height. ± 2 mm in any one storey height or structural bay width. ± 2 mm in alignment in any direction between any two adjoining metal cladding

Construct joints between components to the following permitted deviations:

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Within the length of any joint (including in line continuations across transverse joints) the greatest width shall not exceed the least width by more than 10%. Any variation shall be evenly distributed with no sudden changes. The offset end elevation between nominally in-line edges across a transverse joint shall be not more than 10% of the width of the transverse joint or 2mm. The offset in plan or section between flat faces of adjacent panels across any joint shall not be more than 10% of the width of the joint or 1.0 mm whichever is lesser. 4.4

Installation 4.4.1

Installation of fixings

Install fixings in accordance with their manufacturer’s instructions and procedures. The strength grade combination of bolts, nuts and washers shall be as prescribed or recommended in British Standards. Use a torque spanner to achieve correct tightening of fixings to achieve correct tension load and avoid under / overstressing, Use lock-nuts to prevent loosening. At least one clear thread shall show above the nut. 4.4.2

Metal cladding anchors

Verify correct location and fixing onto the building structure. Clean out all cast-in anchors. 4.4.3

Site Sealant Work

Apply and cure sealants in accordance with their manufacturer’s directions on minimum and maximum temperature and RH conditions. Achieve the depth to width geometry. Prevent three-sided adhesion. Use appropriate backer rods, tapes, surface preparation and primers as manufacturer’s directions. Tool off sealants neatly. 4.4.4

Installation of fire and smoke stopping

Install fire and smoke stopping at all voids and penetrations between compartments at designated locations to achieve the specified fire and smoke stopping performance. 4.5

Protection and Cleaning Protect vulnerable coated surfaces; metal edges, corners and features. Apply temporary removable protection against damage from following trades or operations and the anticipated hazards. Materials used for temporary protection shall be compatible with and subsequently removed from the surface and finishes without detriment to the finish. The component suppliers and finishers shall approve methods for removal. Unless agreed otherwise by the SO protection should remain in place until all work potentially damaging to the components or their finish has been undertaken.

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Replace any damaged components in the metal cladding. Concession to this requirement will only be given if the contractors proposed repair procedure is authorised by the SO and complete and warranted repair of the damage is achieved.

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Submissions 5.1.1

Tender Submissions

Submit the following information with the tender: a. Outline strategic method statement covering the Works. b. Drawings and descriptions of principle components and assemblies. These must illustrate the generic principles involved in the system. c. Material descriptions for main panels and support system. d. The means of attachment to the building structure e. Typical detailing for the metal cladding system for penetrations f.

Name of Contractor’s Professional Structural Engineer

g. Independent Testing Authority to be employed by the Contractor for off site testing metal cladding specimen and on site hose testing h. Details of proposed metal cladding installer i.

Details of any components or materials that will not provide the expected design life together with information on how these materials will be replaced.


The name of the coating applicator

k. Draft warranty identifying warranty periods for the principal components together with any limitations on these


Work Submissions

Upon commencing the work, submit: a. Any outstanding submissions required at tender. b. The location and component referencing system for identifying metal cladding throughout the building c. Drawing list indicating the programme for the production of design information. d. Movements allowed for including provision for all live and dead load movements in the structure and metal cladding, thermal expansions and contractions, moisture induced movements, shrinkages in structure and metal cladding, creep effects or other source e. Typical detailing for the metal cladding system between metal cladding and openings for windows and louvres at head, sill and jamb illustrating junctions with adjacent structure, cladding and finishes roofs and pavements. f.

Metal thickness, jointing details and location of fixings

g. Position of weather and air seals h. Methods of ventilation and drainage of the metal cladding

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The Design Wind Load used (including all local coefficients and calculation method)


Shop Drawings

Prepare shop drawings, which shall include: a. Elevations at a minimum of 1:100 of all facades setting out the panels together with the support system, compartmentation and fire stops. All panels to be individually identified. b. Detail drawings at 1:10 of all panel types c. Details of all junctions at 1:2 d. Details of support fixings at 1:5 Fabrication shall not commence until shop drawings have been reviewed and permission to proceed has been obtained from the SO. Allow 21 days for SO review. 5.1.4

Certification of Materials

Provide the SO with certification from the manufacturer of the following materials/ components, certifying that the respective material is of the correct grade, strength, size, finish, etc, and is in accordance with the relevant codes and standards specified: a. Metal coating b. Metal panel c. Support brackets d. Support rails


Maintenance Submissions Include the following information in the maintenance manual and logbook: a. Cleaning methods for metal panel surfaces


Warranty Submit the warranty for the SO’s acceptance upon completion of the works.


Quality Control Plan Submission Prepare and submit the quality control plan for SO’s acceptance prior to starting work.


Samples and Mock-ups 5.5.1


Subsequent to acceptance of detail design and prior to production, fabricate and build at locations as directed a full size visual mock up for the SO to review. Undertake any modifications throughout the metal cladding system identified from the mock-up by the SO in order to meet the performance requirements and design intent. 27 Version 1.0

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Inspection No items.


Tests 5.7.1

Water-tightness Test to External Metal Cladded Walls


Carry out tests on 10% of the external walls directly facing the exterior.

Source of water

Water used to test the water tank prior to its sterilisation. Sterilise the tank after completion of the water test. Use PUB potable water only for re test.

Method of testing

Provide the following information to the SO for approval eight weeks before carrying out the test: a. The equipment set up to conduct the test b. Procedure of the water test c. Pump capacity to deliver the required flow rate d. Method to suspend the nozzle Fix nozzle 1800mm-2000mm away from the surface of the wall, at an incline of 30º to the external wall as shown in the drawings. Deliver 300 litres of water for 2 hours. Place the nozzle so that it covers the whole wall panel. The panel will be considered to have passed the test if no dampness or seepage appears on the internal surface of the wall panel or adjacent areas during the spraying and within half an hour of completion of the spraying.

Further testing

Should more than 20% of the panels fail the test a further 10% of the panels are to be tested. Should more than 20% of these panels fail all other panels are to be tested.

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