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.
NZS 3604 Timber Framed Buildings is an acceptable solution to comply with the NZBC for light timber frame buildings not requiring specific design.
It contains prescriptive dimensions for purlin spacing and fasteners, based on maximum design wind speeds of Low (32 m/s), Medium (37 m/s), High (44 m/s), Very High (50 m/s), or Extra High (55 m/s). The load calculations for NZS3604 were based on a simplified interpretation of AS/NZS 1170. These values can be used for calculation of loads on the cladding of structures designed using NZS 3604.
Some of the limitations in the scope of NZ S3604 are:
- Timber frame construction.
- Height from lowest ground to the highest point on the roof may not exceed 10 m.
- A snow load may not exceed 1.0 kPa, although Section 15 of NZS 3604 does provide additional criteria for 1.5 kPa and 2.0 kPa snow loads.
NZS 3604 includes:
- private dwellings, hostels, hotels and nurse's homes;
- factories with restricted floor loadings; and
- institutional and educational buildings with restricted floor loadings.
NZS 3604 excludes:
- buildings dedicated to the preservation of human life;
- buildings which may host crowds;
- publicly owned buildings containing high value contents; and
- curved roof construction.
Classification of Wind Zones in NZS 3604 are specific to the site. Because the buildings covered by this standard are limited in size, design tables (but not design wind speed) include a local pressure factor of 1.5 kPa over the entire structure, rather than varying factors according to the position on the roof as required by AS/NZS 1170.