The sheet shall be of best quality of approved manufacturer. The sheet shall be free from cracks, chipped edge or corners or other edges.


Purlins

The sheet shall be laid on the wooden or steel purlins as per drawing. The maximum spacing of purlins shall be 1:6 m in the case of 7 mm thick sheet and 4 m in the case of 6mm thick sheets. The upper surface of the purlins shall be in a one plane so that the sheets shall rest on the purlins without forcing down.





Laying

The sheet should be laid with smooth side upward with a minimum side lap of half corrugated 4.5 cm and minimum end of 15 cm. The side lap should be laid on the side opposite the prevailing monsoon wind. The free overhang of the sheet should not exceed than 40 cm.


Fixing

The sheets shall be fixed to the purlins by nearly of 8 mm diameter galvanized hook bolts and nuts providing a bitumen washer and galvanized iron washer for each bolt and nut before the nut is screwed. Roof ladders or planks should always be used when laying, fixing the sheet to avoid the damage of sheets.





Slope

Roof slope should not be flatter than 1 in 5. The normal slope shall be usually in 1 in 2. In case of roof slopes flatter than 1 in 2 1/2. The end overlap should be 25 cm or more.


Ridges

Ridges should be of the type specified such as plain wing adjustable “serrated adjustable” etc. Ridges shall be of the same manufacturer. The ridges are usually in pairs having the required overlap. The ridges shall be fixed with same galvanized iron J or L bolt and nuts with purlins. Hips if required shall be of un-serrated hips of the same manufacturer.


Wind tiles

Wind tiles should be of 40 mm x 6 mm and shall be fixed at the each ends of the sheets. The fixing shall be done with the same hooks bolts which secure the sheets to the purlins.





Measurements


The measurement shall be taken of the laid finished flat surface in meter square. The laps at the ends and sides shall not be measured. The ridges and hips shall be measured in running meter for the finished along the centre line of the ridges and hips shall be measured in running meter for the finished along the centre line of the ridge or hip. Wind tiles shall be measured under a separate item. The rate shall include all materials and labour, bolts and nuts, washer etc. The rate shall not include roof supporting members such as purlins, rafts etc. which shall be measured separately.