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About Purlins & Girts Now
A major benefit of cold formed purlins made from GALVASPAN®
steel is the ease with which cladding can be fixed.
The relatively thin material of the purlin flange means
that drilling and fixing is one simple operation, using
self-drilling, self-tapping screws with pre-assembled
In non-cyclonic areas, fixing may be through the crests
or valleys of the sheets. On roofs, valley-fixing introduces
some risk of leakage, but on walls it is the usual practice.
Check with BlueScope Steel or your sheeting manufacturer/supplier
for the recommended fixing method for the sheeting product
In cyclonic areas, some claddings should only be crest-fixed.
With the cyclic nature of the loading, thin hi-tensile
claddings can fatigue quickly due to a lack of flexibility
around the valley fixing. The sheeting fails by cracking
around the screw heads. (Again, check with BlueScope
Steel or your sheeting supplier on the appropriate fixing
The secret-fixed decks types of cladding are attached
to clips screwed to the purlins. From a structural viewpoint,
steel cladding properly fixed will always provide adequate
lateral restraint for the top flange. This may not apply
to metals or brittle sheeting materials.