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Type of Fasteners:
One of the following three types of screw fastener shall be used as indicated for the fastening of metal siding, roofs and Interior walls. They shall be stainless steel and of adequate strength.
Type A: Type A sheet metal screws are those having pointed ends and wide pitch threads. This type of screw is used for connecting gauge metal to gauge metal
Type B: Type B self tapping screws are those having flat ends and close pitch threads. This type of screw is for used connecting gauge metal to structural member.
Type AB: Type AB self tapping screws are those having pointed ends and close pitch threads. This type of screw is used for connecting gauge metal to structural member.
Material: Shall be approved stainless steel with cadmium plated finish or acrylic painted and the heads painted to match colour of siding. They shall be of adequate strength.
Size of Fasteners: No 12 or larger size screw fasteners.
Length Fasteners:
The length of type A screw shall be sufficient to engage the gauge metal sheets together with a minimum projection of 1.0 cm beyond the sheet surface.
The length of the type B or type AB screws shall be such as to engage sufficient thickness of supports to which they are attached, to develop the full capacity of fasteners.
After approval or comments by the Owner/Engineer, all drawings shall be stamped as "Final Drawing Approved for Construction". Only drawings identified as such will be released on site for construction.
Drawings shall provide all information required at site for construction and shall include full details regarding dimensions, recesses, openings, embedded parts, etc.
As-built drawings related to the works shall be submitted with soft copy.
The Contractor shall provide an experienced supervisor to ensure that the materials are erected to the manufacturer’s instructions and working drawings.
Wherever possible the sheeting to complete elevations or other areas of cladding forming a defined feature shall be carried out as part of a single operation; all sheets being fixed in an approved sequence continuously from one end to ensure tight fitting at end and side laps.
The sheets forming the cladding shall be erected in a sequence to ensure that there is no noticeable variation in colour and they shall be fixed plumb and level with all fixings accurately lined. All dirt and grease shall be removed from the surfaces of sheeting as the work proceeds.
Sheets having a nap or other texture which necessitates fixing in one direction only shall be clearly marked to indicate the top and bottom of the sheet. Lines formed by horizontal laps and fixings shall be continuous and shall occur at the positions indicated on the working drawings. Approval shall be obtained from the Engineer before sheets are cut on Site.
Where profiled cladding is required to be bent to radius, all bending shall be executed by cladding manufacturer using suitable equipment. Aprons, closures, flashings and other similar fittings shall be formed before delivery to the Site.
Rainwater gutters and supports shall comprise steel sheet plates and must be protected by being hot dip galvanized with minimum weight of zinc coating of 0.250 kg/m2.
The outer surface shall complete with an applied protective coloured finish same as exterior flashing to match the siding.
The layout and sizing of gutters and roof drains shall be designed for the maximum anticipated rainfall intensity at the site, but not less than of 3 mm in 1 minute.
Each dewatering section shall be provided with at least two roof drains and one overflow pipe.
All sheet metal items shall be rigid, true to line and neat in appearance. They shall be designed and manufactured in such a way that both soldering work on site can be reduced to a minimum, and neat and easy installation will be allowed.
Provision shall be made for separating sheet metal items from wood boards and/or concrete/plaster surfaces by means of adequate roofing felt.
Longitudinal slope of gutter bottoms shall not be less than 0.5%.
Box gutters shall be adequately supported and be designed to support rigidly the loads and below permanent flow of water.
Gutter outlets of diameters between 15 cm to 20 cm of UPVC type shall be provided for connection to rainwater downpipes.
Basket strainers of non-corrosive wire for loose installation in gutter outlets shall be provided.
Overflow pipes of 10 cm diameter and of lengths between 50 cm and 80 cm shall be provided. The projecting part from the outer alignment of exterior walls and/or siding shall not be less than 25 cm. Overflow pipes to be routed through concrete and/or masonry parapet walls shall be wrapped by means of adequate roofing felt.
Provision shall be made for expansion joints in box gutters, wall flashing and cap strips etc. The expansion joints shall be adequate for the type of work specified. They shall not be spaced more than 10.00 m.
2. NON- CORROSION RESISTANT COATINGS for architectural applications such as airports, schools, commercial centres…
Steel Sheets Roofing, Wall and Accessories
Cladding to roofs and walls shall consist of Urethane TF top coat ( PVC resin coatings are not allowed) over Versacor flexibilized epoxy barrier coat applied over primer to galvanized steel sheeting (G90, ASTM A653) of the thickness and types specified hereafter. It should be designed to withstand the loads and climatic conditions prevailing at the site and to give a standard warranty of fifteen (15) years.
The colour of cladding shall be selected to comply with the overall architectural concept of station development and shall be subject to the Engineer’s approval.
The cladding to the walls and roofs of the buildings shall not be erected until such times as the concrete pavements within and around the buildings have been completed.
Insulated composite roof panels shall consist of factory finished steel sheet and thermal insulation by approved manufacturer. The panels shall be manufactured using the following materials.
General
The panels shall be of a width and a thickness chosen from the manufacturer’s standard range to meet the specified insulation requirements. The panels shall be manufactured in precise lengths to suit the structure in order to minimize end laps.
Weather tightness
All completed siding and roofs shall be weathertight, watertight
Provision shall be made, in the design of insulated siding, to drain to the exterior of the
siding any condensation taking place within the assemblies.
The roof slope shall be as shown on the drawings. In no case shall it be less than 4o.
External Weathering Sheet
External wall cladding Panel: Exposed fastener type cladding system, 914mm cover width with bottom flutes of 104mm and top flutes of 35mm. Total cladding thickness approximately 38mm.
External roof cladding Panel: Exposed fastener type cladding system, 914mm cover width with bottom flutes of 104mm and top flutes of 35mm. Total cladding thickness approximately 38mm.
External surface coating of cladding: A multi-layered system with a nominal 35 microns Urethane TF top coat, with a nominal 75 microns Versacor flexibilized epoxy barrier coat primer coat applied to min. 0.76 mm thick galvanized steel base metal. Total coating thickness to external surface shall be not less than 110 microns.
PVC resin coating system on the external surface is not acceptable.
The coating system performance shall be complying with the following standards:
· Humidity Resistance Test: No effect should be measured after exposure in a humidity
chamber and exposed to 95% - 100% relative humidity for 1500 hours at 30oC with
unprotected edges, all in accordance to ASTM 4585.
· Salt Fog Test: No effect should be measured after continuous surface condensation
exposure of 5% salt fog at 30oC for a minimum 2000 hours. Each panel is scribed with an
“X” prior to commencement of the test procedure and edges are protected by wax, all in
accordance to ASTM B-117. Evaluation of the results is to be inspected in accordance to
ASTM D-714.
· Abrasion Resistance Test: The ‘Falling Sand Method’ in accordance to ASTM D-968 to a
minimum of 510 litres.
· Colour Change Test: Measured by QUV test method, a value of 3.92 in accordance to
ASTM D-2244 after cycles at 4 hours UV at 60 oC and 4 hours condensation 50 oC for
2000 hours.
· Pencil Hardness of paint on coating to be Scratch Hardness 2H and Gauge Hardness of
HB in accordance to ASTMD3363.
· Kesternich Test :After 30Cycles of Acid Rain and Cyclical Test, there is no
significant blistering ,colour change or loss of adhesion in accordance to ASTM G-87.
· Acid and Alkaline Test in accordance to ASTM D-1308-87(1993)
Thermal insulation shall be rockwool or fibreglass, with a thickness chosen from the manufacturer’s standard thickness range to meet the overall coefficient of thermal transmission U for insulated siding, roofs and interior walls shall not exceed 0.75 W/m2/oC in still air. The installation shall be non-hygroscopic and fire retardant and shall resist attack by micro-organism, fungi, vermin, insects and mildew.
The internal sheet shall conform to the following:
ii) An epoxy, anti corrosive zinc and primer shall be applied to the internal face to a dry film thickness of 5 microns.
iii) A grained off-white silicon polyester finish coat shall be applied to the internal to a dry film thickness of 15 microns.
Single skin steel cladding shall comply with the requirements of Clause 25.2 external weathering sheet.
Shape of Steel Sheet
i) Roof – Trapezoidal corrugation shape
ii) Wall - Trapezoidal corrugation shape
Exterior flashings shall be fabricated from materials of the same material, colour and finish as described from the external weathering sheet of the composite roof panels. They shall be formed so that the prospective coating are not damaged or impaired.
Internal flashings shall be fabricated from materials as described for internal sheets. Corrugation closures shall be installed as recommended by the composite roof/wall panel manufacturer to form a weather tight installation.
Type, application and positions of sealant shall be as recommended by the composite roof/wall panel manufacturer. In general, all site and end laps shall be sealed with butyl mastic or equivalent during the course of erection. Filler strips shall be provided at both ends of all sheeting runs and shall consist of PVC form plastic. All material used shall be suitable for the climatic conditions prevailing at the Site.
i) The substrate shall be same as the external weathering sheet. |