The material and performance of the fastener is not something that we would generally specify or make any specific recommendations on other than following recognised good industry practice.
It is generally now accepted that for cladding systems and rooflights incorporated into them to meet their long-term non-fragile expectations of up to 20 years and longer, then good quality stainless steel product should be used.
For further guidance on fasteners, sealing washers etc, and their suitability for the application, please refer to the appropriate fastener manufacturers.
