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 wind load imposed on a roof structure is taken to apply perpendicularly to the roof cladding over a nominated area. The design wind load is affected by the pitch of the roof and is modified using factors called pressure coefficients. Wind design load is measured in kilopascal (kPa); 1 kPa equals 1 kN/m².
AS/NZS 1170.2 and NZS 3604 contain the basic wind speed regions for New Zealand and the modifying factors that govern the design wind load. The predominant wind speed for New Zealand is 45 m/s. The exceptions are either side of Cook Strait and areas in the lee of mountainous areas.