In accordance with recommended industry practice, and to ensure that the expected non-fragile rating is achieved, sufficient overlap should be allowed for on-site tolerances so that the fasteners can be installed a minimum of 50mm from the sheet end. For site assembled rooflights, we normally recommend that the sheets be ordered to provide a 150mm minimum overlap to the outer sheets and 100mm minimum for the liners.
Composite panel rooflights, or FAIRS, are best ordered with provision for a 150mm overlap, and purlin spreader plates or ledger angles provided to ensure adequate support of the panel ends. Please see fitting instructions for site-assembled and composite panel rooflights.
