Fastners

Researches executed on causes of steel building failures worldwide indicate that almost 80% of failures start from the fasteners. Since fasteners, used on cladding and structure together, constitute roughly 6-8% of the entire project cost, several builders have the tendency to neglect this vital aspect of their project. Fasteners used on steel Roof and Wall Cladding must be of good quality and properly galvanized conforming to IS: 730 standards. This will go a long way in providing a weather proof and long lasting roof. Different components of good quality fasteners are depicted below in Figure-8.
There are various kinds of hooks and screws available in the market depending upon the material and type of purlins on which sheets need to be fixed (Figure-9). G.I. Hook Bolt should be used for fixing sheets to angle Iron purlins. G.I. Crank Bolt should be used for fixing sheets to channels or rectangular/square tubes purlins. G.I. Coach screw (square head) should be used for fixing sheets to wooden purlins only.
The rubber washer should be 25 mm in diameter and 3 mm thick with 6 mm bore to suit 8 mm diameter bolts. This bond between rubber washer and bolt ensures water proof sealing. The G.I. flat washer is 25 mm in diameter (if it is a round washer) and 1.60 mm thick with central hole to suit 8mm diameter fixing bolt or screw. The sheets are fastened to purlins (in case of Roof Cladding) or side girts (in case of Wall Cladding) by minimum 8 mm diameter hook bolts at a maximum pitch of 375 mm.