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.
The periphery of all roof planes should be sealed with a flashing.
Longitudinal flashings must cover one or two crests according to requirements. There should be a gap between the downturn and the adjacent rib to prevent capillary action and to allow for pressure equalisation. Both vertical and horizontal faces of the flashing should be fastened to other cladding or preferably, through the cladding to the structure.
Transverse flashings may be notched over the ribs of the profile, or for lower trapezoidal profiles or corrugate they can be fitted with a soft edging which is dressed into the pan of the profile. All soft edging must be colour matched to the roof before installation. Soft edging can be solid aluminium, solidly backed, or perforated to allow ventilation. The leading edge of transverse flashings must be through fastened to the primary structure, not riveted to the cladding.