Roofing and Ceiling

Roofing 

a)  General 

1. See that  timber is of correct species, of natural  growth properly  seasoned and of correct dimensions. Check moisture content. 
2. Check the  assembled truss and its joints in detail before hoisting. See that proper contact surfaces are provided for supports. It is impossible to examine trusses after erection. A single bad joint  in a Truss is sufficient to cause failure a roof and may result in a serious accident. Trusses passed should be  marked so that it can be checked even  after erection. 
3. See that holding down bolts are in position and are properly fixed and than trusses are properly  secured to them. 
4. Check if wedges  and cotters have been provided so as ro allow  possible adjustment later and  that the truss has adequate camber. 

b)  CGI/CI Sheets 

1. See that corroded sheets are not used. 
2. See that proper galvanized hook bolts, coach screws and washers are provided  and that these are set in white  lead. 
3. Holes must be made in the ridges  and  not in the valleys of the corrugations. These holes must be punched from the underside or drilled. 
4. The side overlap must not be less than 1% corrugation. The end  overlap must not be less than 15 cms. 
5. See that sheets are concretely aligned so that the ridges and valleys of the corrugations of the sheets are in straight lines. 
6. See that  stitch bets are provided where specified. 
7. Ensure that the portions of CI sheets covered by the  laps are painted before the sheets are assembled and fixed. 
8. Lay the sheets starting from the side opposite to that of the prevalent monsoon wind  and ensure proper flashing of ridge caps, aprons and louvers. 

c)  AC Sheets 

1. See that no broken or cracked sheets are used. 
2. Study carefully the chart issued by ACC sheet manufacturers showing the number and position of hook bolts, the correct method of fixing and fitting AC sheets. See that these instructions are carefully followed and bitumen and  diamond washers are used as specified. Try to arrange sheets so that where corners have to be cut, sheets with  damaged corners are used first. Where sheets have to be cut, use cracked sheets so as to obtain the maximum salvage value from damaged sheets. 
3. Warn all concerned before laying AC sheets that sheets are not to be screwed or bolted down too tightly. If they are too light, breakages are bound to occur in the hot weather on expansion of the sheets. 
4. See that all holes are drilled on the ridge and that the diameter of the hole is 3 mm larger than the diameter of the  hook bolt,coach screw. 
5. Ensure that the length of the hook bolt/coach screw is adequate in relation to the depth of purlins and situation of the sheets as intermediate sheets c~r  corner sheets. 
6. Ensure that where four corners are coming at point, two sheets are mitered. 
7. See that the end lap between the sheets is at least 15 cm. 
8. See that the sheets are correctly aligned with reference to purling so that the hole in the sheet is 7.5 cm from the edge and that purlins are straight. 
9. See that  hook bolts/screws are staggered in the semi-corrugated sheets for the intermediate corrugation. 
10. See that cat  ladder or roof  board is used by workman  working on the roof to avoid damage to sheets. 

d) Tiles 

1. See that no broken or cracked tiles are used. 
2. See that nibs or lugs rest  fully on the supporting batten  at lower level of tiles. 
3. See that all tiles fit closely to adjacent ones and that overlapping is to the full depth. 
4. See that rows are even, straight and paralled to the ridge. 
5. Where hales are required lo be pointed, plastered, set in  lime or cement mortar or  require filling of ends, these shall be soaked in water for two hours before use and cured subsequently. 

e)  Flat Roofs 

1. See that correct slope is given in  the slab and padding concrete as per drawings and specification. 
2. See that smooth surface or paper is provided under the ends of slab.