Side Lap Fixing Between Purlins
When side lap fixing GRP to metal, an oversize hole should be pre-drilled in the GRP and a coarse thread Type 17 screw used with a profile metal washer and EPDM seal.
When fixing GRP to GRP, a rubber-nut or grommet can be used and installed from the top side of the roof sheet using a 35 mm long, 4.5 mm diameter, aluminium or stainless steel gutter bolt and a 20 mm diameter metal and EPDM sealing washer.
Alternatively, if Bulb-Tite rivets are used a clearance hole is required, and care should be exercised when setting the rivet to avoid stress at the connection. This fixing is not suitable for use in high design wind load areas.
When fixing tray decking profiles and using matching roof lighting sheets, there are several fixing options depending on the configuration of the profile. The independence of the metal and plastic sheeting should be maintained with all profiles to allow for their differing rates of expansion.
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