A1-50 Architectural Precast Concrete Cladding
A1-50 Architectural Precast Concrete Cladding
A1-50 Architectural Precast Concrete Cladding
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CONTENTS
Page
1. GENERAL 3
1.1 Scope 3
1.2 Related Sections 3
1.3 Standards 3
1.4 Trade Preamble 4
2. PERFORMANCE REQUIREMENTS 7
2.1 Contractor’s Brief 7
4. WORKMANSHIP 19
4.1 Design and Selection of Architectural Quality of Finish 19
4.2 Fabrication 19
4.3 Fabrication and Installation - Handling 23
4.4 Pre-cast Concrete Panel Installation 23
4.5 Site Sealant Work 24
4.6 Installation of Fire and Smoke Stopping 25
4.7 Site Repairs 25
4.8 Siloxane Treatment 25
4.9 Protection and Cleaning 25
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1. GENERAL
Read with the General Requirements section, and all other contract documents.
This document is supplementary to Section A1-50 Architectural Precast Concrete
Cladding of the NPQS, and sets out Project Specific data, in the same clause
headings as in the NPQS. All modifications and additions noted in this document take
precedence over clauses noted in the NPQS.
1.1 Scope
This section covers the requirements for architectural aspects of precast concrete
cladding including elements such as façade panels, screens and sunbreakers. It
covers mainly the finishes aspect of the precast elements. Requirements for concrete
and reinforcement are set out in the structural specifications.
Use in combination with section A1-20 when precast units incorporate windows
installed at the precast yard. Use in combination with section A1-60 when precast
units incorporate stone claddings.
1.3 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
SS CP33 Lightning protection
SS CP81 Precast concrete slab and wall panels
SS CP65 Structural use of concrete
SS 26 Ordinary Portland cement
SS 31 Aggregates
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1.4.1.5 Methods
Propose method of fabrication, erection/installation.
1.4.1.6 Weather/waterproofing
Propose details of weather/waterproofing.
1.4.6 Warranty
Provide a ten-year warranty in accordance with contract conditions for the entire
cladding system including all components and accessories for the specified
performance.
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2. PERFORMANCE REQUIREMENTS
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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.
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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
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 precast 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 PSD for design movements and deflections to account for.
Where the window adjoins the main structural frame or is adjacent to a vertical
movement joint account for design movements and deflections as follows:
Maximum Edge Beam Deflection due to:
Self Weight mm or L/500
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2.1.8 Functionality
2.1.8.1 Appearance
Achieve the mandatory geometry and presented on the architectural drawings.
Achieve colours and appearances presented on the architectural drawings.
Submit sample panels to illustrate the proposed surface colour, texture and variability.
2.1.8.2 Drainage
Design and install so that drainage of rainwater is predominantly at the outer face.
Provide secondary drainage at panel joints.
Provide continuity of watertightness within internal drainage routes at all panel
junctions.
Ensure that drainage provision does not permit insect entry into drainage routes.
Ensure continuity of weathertightness to adjacent roof waterproofing finishes and
upstands.
Ensure disposal of rainwater from precast concrete panels into rainwater disposal
system.
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2.1.8.3 Infestation
Resist attack or infestation by micro-organisms, fungi, insects, reptiles, birds or bats
and rodents.
Have no openings in or around the precast concrete cladding that permit entry of
insects, reptiles, birds or bats and rodents.
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2.3 Concrete
2.3.1 General
Refer to structural specifications for requirement of concrete constituents and mix
design.
2.3.2 Retarders
Submit name, source, type, dosage and justification for use to SO for review.
2.3.3 Cement
Obtain all cement from a single source for the whole of the Works.
Deliver and store all cement in sealed containers.
Do not use super-sulphated or high alumina cements.
2.3.4 Water
Obtain water from PUB.
2.3.5 Pigments
Comply with the requirements in BS EN 196.
2.3.6 Sulphates
Do not exceed Total acid soluble sulphate (SO3) content of the concrete mix of 4% of
the mass of the cement in the mix.
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a. Cream emulsion,
b. Neat oil with surfactant added
c. Chemical release agent
2.3.8 Reinforcement
Refer to structural specifications on Reinforcement.
2.4 Moulds
Refer to structural specifications on Precast Concrete works. Take account of the
architectural finish required. The following are probable finishes:
a. Smooth off form
b. Water washed
c. Honed or polished
d. Sandblasted
e. Acid etched
f. Bush hammered
g. Form liners
h. Brick or tiled face
Retain specialised moulds for 1 year after completion.
2.5.1 Stone
Refer to section A1-60 clause 3.3 for selection and testing of stone. Refer to clause
2.2 for selected stone.
Determine stone thickness and submit calculations
Determine stone panel layout and joint widths to meet architectural design intent and
tolerances on stone.
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2.5.3 Sleeves
Use Polychloroprene sleeves around pins and clips in stone.
2.7 Insulation
Thermal insulation shall (be / have):
a. Inert, durable, rot and vermin proof, CFC and HCFC free.
b. Not support mould fungal or bacteria growth.
Allow for reduced performance of insulation due to the effects of moisture and ageing.
2.8 Waterproofing
2.8.1 Membranes
Membranes within the precast concrete 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.
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2.8.2 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.
2.8.3 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.
c. Silicone sealants shall comply with BS 5889.
Refer colour selection of any visibly exposed sealants to the SO.
2.8.4 Baffles
Use polychloroprene baffles, hung from stainless steel pins and draining sequentially
outwards.
Size baffles to accommodate joint tolerances and building movements.
Refer to SO for colour.
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Isolate all galvanised steel and aluminium 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.
2.10.1 General
Comply with 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.
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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.
2.12.1 General
Use stainless steel fixings and fasteners to BS EN ISO 3506 wherever wetting may
occur.
Use carbon steel bolts with carbon steel components in dry locations only.
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.
2.12.2 Brackets
Use stainless steel 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
precast concrete cladding.
Allow for construction tolerance in the all components and structure.
Adjust by small increments in and out, up and down and side to side
Use lock nuts to prevent loosening due to movements and/or vibrations.
State the torque values for tightening all bolts on the drawings submissions.
State the maximum allowable shim dimension on the drawings submissions. This
shall not be greater than 10mm.
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Allow for resulting dead and applied loads in precast panel and fixing bracket, anchor
design.
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3. WORKMANSHIP
3.2 Fabrication
3.2.5 Concreting
For assembling reinforcement cages, casting, curing, and striking, refer to structural
specifications on precast concrete works.
3.2.6 Finishes
Remove spacers and surface contaminants / debris trapped in face.
Apply any post applied surface treatments required to achieve the architectural
quality finish.
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3.4.1 General
Install in accordance with BS8297, section 11 and the Architectural Cladding
Association “Code of Practice for Safe Erection of Pre-cast Concrete Cladding”.
3.4.4 Tolerances
Achieve tolerance of erection as specified in BS 8297, section 11.5.
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3.4.6 Fixings
Install fixings in accordance with the requirements of clauses 11.3.4 and 11.3.5 of
BS8297 to correct torque and in accordance with their manufacturer’s instructions
and procedures.
Ensure the strength grade combination of bolts, nuts and washers as specified.
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.
Ensure allowance for movement where required at fixings and dowels.
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3.10 Submissions
Read in conjunction with submission requirement of structural specifications on
precast concrete works.
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3.10.4 Installation
a. Proposed locations for hose test.
b. Site hose test results and certificates.
c. Proposals to address any shortcomings identified in hose testing.
d. Site hose test reports and remedial measures.
3.10.6 Warranty
Submit the warranty for the SO’s acceptance upon completion of the works.
3.11.1 Samples
Submit samples, prototypes and demonstrations of fabrication and installation as
required by SO.
Following review of samples, prototypes and demonstrations all subsequent materials
and workmanship are to be the same or better standard.
Four sample panels to illustrate the major junctions of the elevation.
3.11.2 Mock-up
Refer to the PSD for requirement of mock-up panels for the project, if any.
Provide the following mock-ups for the project:
Sample/Mock up Requirement/locations
3.12 Inspection
SO to inspect all pre cast panels before they are delivered to site.
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3.13 Tests
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