Site Analysis
Understanding all the features of a site, using and protecting the best, and minimising the impact of the worst.
New Zealand Climate/Environmental Zones
Three climate zones are used in climate-related NZ Building Code compliance documents (for example, compliance document H1/AS1 on energy efficiency). These climate zones are based on average temperature data and take in to consideration territorial authority boundaries. It is useful to be familiar with these zones.
Zone 1, covers Northland, Auckland and the Coromandel Peninsula
Zone 2, the rest of the North Island other than the Central Plateau
Zone 3, the Central Plateau of the North Island and the whole of the South Island.
For example, in climate Zone 3 – the colder regions of the country – designers must provide greater levels of thermal insulation in the buildings.
See climate zone maps from Standards New Zealand.
Wind, earthquake, and snow zones
The country is also divided zones based on other features. Under NZS 3604 Timber framed buildings, every site in New Zealand is classified into different wind, earthquake, snow load and corrosion zones.
The simplified and generally conservative classifications for a particular site provided by NZS 3604 may be in the LIM report available from the local council. Designers must also factor in site specific wind strengths and design accordingly.
NZBC Clause E2 External moisture includes compliance document Acceptable Solution E2/AS1 which provides a means of assessing weathertightness risk factors associated with a building’s design. One factor considered is the wind zone from NZS 3604.
AS/NZS 1170 Structural designs has methods and maps to determine wind, earthquake, snow and ice actions for a specific building/site from engineering first principles. More economic structural designs should result in some cases if the more detailed provisions are followed. A registered engineer will be required to undertake design to this standard.
Corrosion zones
Definitions of corrosion zones are provided in both NZS 3604 Timber framed buildings and AS/NZS 2428. Under NZS 3604 a building site is classified as being in one of four zones or in a sea spray zone depending on its location. This classification defines the severity of exposure to wind-driven sea salt or to geothermal gases.
This means that you will need to consider durability of building materials, especially claddings, flashings and metal fastenings. For example in the seaspray zone subfloor fixings are generally required to be stainless steel.
For cladding use in corrosive environments refer to a product appraisal or the specific manufacturers product information.
A LIM report may identify the corrosion zone as determined by the local council.
NZS 3101 Concrete structures has exposure classification maps which indicate coastal corrosivity zones and typical wind speeds and directions for New Zealand together with enlarged maps of the major cities.