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ACC Sheet Roofing
ACC Sheet Roofing
An asbestos sheet is a type of Construction material that is made from asbestos Cement. It was used in residential, commercial and industrial Construction applications. ACC Sheet Roofing typically used as roofing or siding.
Asbestos cement sheet roofing have to contain whether corrugated sheets or semi corrugated sheets as specified. The sheet must be with approved quality and should ensure IS: 459. The sheet is free of cracks, damaged edges or corners along with other damages. The slope of the roof is not less than 1 to 5. Typical slope adopted commonly is 1 to 3.
Layout of ACC Sheet Roofing
★The sheets must be laid on Purlins as well as other roof members as advised in the drawing.
★The lines of corrugations are truly parallel to the sides of the area to be covered. Purlins spacing should not exceed 1.65 meters.
★Each sheet must be laid by using a minimum lap of 15 cm at the ends.
★For corrugated sheets the side lap must be half a corrugation whereas for semi corrugated type it must be one corrugation.
★The sheets must be placed on smooth side.
★The sheets must be attached to Purlins by way of galvanized hook bolts or crank bolts of approved type and size.
★The diameter of bolts must not be less than 8 mm.
★The holes for bolts are drilled (not punched) in the ridge of corrugations while sheets are on the ground.
★The holes are not drilled in valleys.
★Hole-diameter is actually 3 mm more than bolt diameter.
★Each galvanized bolt must have a bitumen washer and a galvanized washer placed over sheet prior to the nut is screwed down from above.
★The nut must be tightened to make the joints leak proof.
★Wind ties should be provided on ACC sheet roofing in order to save it from disaster etc.
★Proper ridges must be provided where it is required based on the site condition.
★For drainage of rainy water through pipes proper valley gutters should provided in case of multi span sheet roofing.
Layout of Asbestos cement sheet roofing
Common Defects during erection of A.C.C. Sheet Roofing
⚙Sheets are punched instead of drilled to make holes into bolts.
⚙Wrong holes are created at some places and they are not closed in later.
⚙Lap length of sheet is not proper.
⚙Cracked sheets are used.
⚙Hooks’ bolts are loose.
⚙Length of hooks’ bolts is not according to specification.
⚙Bitumen and G.I. limpet washers used are of below standard.
⚙Bitumen washers are not provided at some places.
Benefits of A.C.C. Sheet Roofing
👍It is cost effective.
👍It covers more space with less intermediate supports.
👍It stays cool as it observes less heat.
👍It takes less time for fixing when compared with RCC roof.
Disadvantage of A.C.C. Sheet Roofing
✎Problem of damage and leakage
✎It can’t be used for second storey.
✎This is not so safe against disaster.
Raw Materials used for A.C.C. Sheet Roofing
✓ACC sheet
✓Hook
✓Bolts
✓Bitumen and Steel Washers
✓Nuts
✓Frame /‘Purlins’
✓Ridge and Hip Cap
✓Metal Valley