Code of Practice v3.0 Online
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.
Exposed flashings are typically manufactured using the same base metal material as used for the roof and wall cladding. If flashings are required to match the colour of the profiled cladding, it is necessary for the pre-painted flat sheet or coil to be made by the same manufacturer, using the same process. When it is not possible, or if different materials are intended or specified, the alternative materials should be compatible considering both contact and runoff. (See 4.9.4 Compatibility Table)
All flashings must be fabricated from a ductile material and designed for lateral strength by folding, stiffening, or ribbing on external edges, with a maximum unstiffened width of 300 mm.
Vertical faces of flashings such as barges and fascia can exhibit oil canning. This can be minimised by using heavier gauge material, by forming stiffeners, or by providing clip fastened attachment systems which allow for thermal movement. In critical visual areas, the COP recommends a maximum unstiffened depth of 200 mm on the vertical face.
Metal flashings must have a bend radius complying with the minimum radii prescribed in 4.10.8 Microcracking.
The minimum thickness for metal flashings must be:
- Coated steel — 0.55 mm,
- Aluminium — 0.70 mm,
- Copper — 0.60 mm,
- Zinc — 0.70 mm,
- Stainless steel — 0.45 mm.
Proprietary EPDM penetration flashings are detailed in 9.5 Boot Flashings.