The NZ Metal Roof and Wall Cladding Code of Practice is a comprehensive design & installation guide, and a recognised related document for Acceptable Solution E2/AS1 of the NZ Building Code.
On most pierce fixed roofs, mode of failure is likely to be pull-over. Where profiled load spreading washers are required to eliminate this, it is important that the specified washer is used. When fastening to light gauge steel purlins, thread strip out may be the lower failure point. The pull-out failure point is very dependent on drill point, thread shape, and pitch; it is essential in such cases to use a correctly specified fastener.