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 recommended overhang for roof cladding with a pitch between 10° and 35° is 50 mm, and 40 mm is regarded as suitable for a roof above 35°. When the ends of the ribs are not baffled by a spouting and the pitch is below 10°, the overhang should be increased to 70 mm to avoid blow-back.
Underlay must not overhang the gutter line by more than 20 mm, or if eaves flashings are used, terminate on the upper side of the flashing. Do not drape underlay into the gutter.