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Regions
You can select Regions A, B, C or D for any building.
The Region required for any building will generally be dictated by the local council for the area in which it is to be built.
Region Definition:
Wind regions are pre defined for all of Australia by Australian Standard 1170.
The Wind Region has nothing to do with surrounding topography or buildings.
Most of Australia is designated Region A which indicates a Regional Basic Wind Velocity of 41msec.
Some areas are designated Region B (49msec). Local authorities will advise if this applies in your area.
Region C areas (57msec) are generally refered to as Cyclonic and are generally limited to northern coastal areas. Most Region C zones end 100km inland.
Region D (69msec) Australia's worst Cyclonic Region between Carnarvon and Pardoo in Western Australia.
A note on W values:
The W system was introduced years ago as a simplified way of describing the wind capability of buildings. Since then it has been dropped by the Australian Standards as being too arbitary and possibly misleading.
However many builders, shed companies and even authorities still cling to using it.
There is no direct relationship between W values and the currently ASA approved Region/Terrain Category system because the W system was derived from an earlier system which included allowance for a Return Period amongst other things which is no longer used in the standards.
The best way to deal with requests for W value buildings is to explain that you use the currently approved method of describing a buildings capabilities in terms of Region and Terrain Category and design for the applicable Region and Terrain Category as described.
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