Four earthquakes zones - zone 1 to zone 4 - are shown on a map of the North and South Islands in Figure 5.4 of NZS 3604:2011 Timber-framed buildings.
The earthquake zones in BRANZ Maps are modified versions of those. The zones are modified so that they better align with NZS 1170.5:2004 Structural design actions - Part 5: Earthquake actions - New Zealand.
BRANZ Maps also include the changes to the zone boundaries in the Canterbury region introduced by the New Zealand Building Code clause B1 compliance document published in August 2011.
Three exposure zones - zone B, zone C and zone D - are shown on a map of the North and South Islands in Figure 4.2 of NZS 3604:2011.
The corrosion zones in BRANZ Maps are our interpretation of the exposure zones in NZS 3604:2011.
The zones relate to the severity of exposure to wind-driven salt, with B being low risk, C medium risk and D high risk.
Zone D includes:
- all offshore islands
- the area within 500 m of the coastline of New Zealand, including harbours
- the area within 100 m of tidal estuaries and sheltered inlets.
BRANZ has not attempted to define precisely what is or isn't a tidal estuary or sheltered inlet, so our maps are technically conservative in those areas.
Building Code compliance document E2/AS1 (2011) includes an exposure zone E, which is beachfront regions subject to rough seas and surf beaches. NZS 3604:2011 contains the comment: "For the purposes of NZS 3604, the corrosion protection requirements for structural fixings in exposure zones D and E are identical..."
Microclimatic factors need to be considered in all locations.
Wind regions and lee zones are our interpretation of Figure 5.1 in NZS 3604:2011.
Wind zones are an output from a 2014 research project at BRANZ. The project aimed to see if the calculation of wind zones (in accordance with NZS 3604:2011) could be automated using GIS (geographic information system) software. The method for calculating wind zones in NZS 3604:2011 is a simplification of the method described in AS/NZS 1170.2:2011 Structural design actions - Part 2: Wind actions.
Several approximations were made in the process of creating the map. Therefore, the wind zones must be treated as indicative and used only as a reference when calculating site-specific wind speed or only in the absence of more reliable data being available.
For example, an up-to-date council-wide wind zone map would be considered higher-resolution data, and a site-specific wind zone calculation would be higher still.
Initial user testing has shown that the wind zones in BRANZ Maps are likely to be inaccurate near escarpments or cliffs.
A description of the method used and a comparison with the few existing council maps can be found in Build 147.
Climate zones 1 to 6 are taken from Appendix C in H1/AS1 and H1/VM1 5th edition amendment 1. Climate zone boundaries consider climatic data and territorial authority boundaries. Appendix C has a map and a table showing which zone(s) apply to each territorial authority.
Rainfall intensity values are sourced from NIWA's HIRDS calculator and correspond to a 10-minute rainfall intensity with an annual probability of exceedance of 10%. These values can be used in conjunction with clause E1 of the Building Code. For other storm durations, consult the HIRDS calculator