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.
