We’ve all seen the devasting impact cyclones and tropical storms can have on both individual homes. It’s therefore essential that your home is built to withstand any challenges the weather and environment may throw at it. Wind classification ratings indicate how easily you are a means of determining the structural requirements of a new house to stay safe in a specific region. For example, homes on the Northern Queensland coastline will have to be able to withstand stronger winds than houses down south.
In this article, we’re seeing which way the wind blows when it comes to wind ratings for new homes! We’ll take a look at the possible classifications and what each means, how wind ratings are determined and what a wind classification means for you and your home.
What are the different wind classification ratings?
On the Beaufort scale, wind classes can be separated into non-cyclonic (N) and cyclonic (C) zones. Different regions will have different gust wind speeds and this is signified by a number (for example, N3 or C4). Below is a quick rundown of the different wind classifications, what each wind class indicates (gust wind speed) and both serviceable wind speeds and the ultimate limit of each rating.
| Normal Zone | Cyclonic Zone | Serviceable Wind Speed (km/h) | Ultimate Wind Speed (km/h) |
| N1 | 86 | ||
| N2 | 86 | ||
| N3 | C1 | 115 | 180 |
| N4 | C2 | 140 | 219 |
| N5 | C3 | 169 | 266 |
| N6 | C4 | 198 | 310 |
What are the Australian standards for wind rating for new homes?
There are currently two standards that are the basis for wind rating classification in Australia which are:
- AS 4055:2012 (this usually applies to residential housing — is the standard from which a wind rating is based.)
- AS/NZS 1170.2:2011 (used when the geometric limits of AS 4055 are exceeded. For example, a roof height is over 8.5m — this will help create a design that is suitable and safe.)
How is a wind classification rating determined?
Wind region
Australia is an enormous country and therefore weather and climate can be quite different depending on where you are. To reflect this, Australia is divided into four regions for wind classification. These are simply called A, B, C and D. The vast majority of Australia falls in Region A. Region B is considered an intermediate zone. Region C covers Northern Coastal areas where tropical cyclones are much more likely, while Region D is a portion of the Western Coast that is especially vulnerable to severe tropical cyclones.
Region A: Normal
Region B: Intermediate
Region C: Tropical Cyclones
Region D: Severe Tropical Cyclones
To help you visualise these regions, here is a map:
Terrain category
The terrain surrounding your building plays a major role in affecting wind speed and flow. For example, wind blowing through a flat plain will have a different speed and flow to wind blowing in a mountainous, forested area. Below are the categories your site can fall into.
Category
1 (TC1) Open and plain terrain
1.5 (TC1.5) Mostly open and plain terrain with bodies of water
2 (TC2) Open terrain with some scattered trees and some isolated structures (between 1.5m and 5m high). Around 2 structures or trees per hectare.
2.5 (TC2.5) Open terrain with some scattered trees and isolated structures
3 (TC3) Open terrain with little to no isolated trees or structures
Shielding factor
Large trees, hills, structures or other obstructions may provide a shield to your home, and thereby minimize the impact of a wind. This can ha
Full Shielding (FS): 10 houses per hectare or
Partial Shielding (PS)
No Shielding: Your house has few or no structures or trees to shield it.
Topography effect
A house built on top of a hill is going to cop more from strong winds than a house built in a valley. This doesn’t mean the house in the valley is impervious, simply less vulnerable. Engineers can conduct a topographic survey to better understand your landscape and how it will interact with various climates.
Why is a wind rating essential for a new build?
A correct wind rating serves a similar purpose to other site works, such as a soil test or topography survey, in it provides insight into what needs to be considered for your next build. Buildings need to factor their environments into their design to make them viable. Knowing the wind rating of a site helps determine which home designs are viable and which are not.
How will a wind rating impact a new build & design considerations?
An accurate wind classification helps your builder and structural engineer know which specific design considerations and building elements need to go into your home to ensure it is stable and safe. Houses in regions C and D will need additional support in the house design.
The bracing design may need to be specifically designed to suit your wind rating. This can affect your choice of material types, spacings, fixings, bracing unit per frame and wall cladding. Elements like windows and trusses are also an important consideration in vulnerable regions, as they’ll need to withstand hurricane winds. Your builder should be aware of the necessary design precautions they’ll need to take to build a safe house in the area.
Will a wind rating impact property value?
Possibly, but it depends on a variety of factors. A high wind rating is unlikely to improve your property value, but if there are enough other desirable factors about your property, it won’t be a deal breaker. Land in areas that are in Region C or D tends to be cheaper than those in capital cities due to a range of factors, including demand, travel distance to various facilities, etc.
Will a wind rating impact home insurance?
When purchasing insurance for your new home, it’s vital you sign up for a policy that will provide adequate coverage for your living situation. If you’re building a house in an area vulnerable to extreme weather conditions – whether it’s bushfires, floods or indeed, tropical cyclones – you’re insurance prices are likely to rise. Therefore, a higher wind rating will likely add to your overall insurance costs, however, it’s best to talk to your financial advisor to find the best deal and policy to suit your needs.
Buildi is here to help you throughout your building journey!
Ready to build your new home, but feel a little overwhelmed with the whole process? This is to be expected even if you’ve done this before. Luckily, Buildi is here to help you every step of the way. Whether you’re looking for a builder for your next project or want someone on your side during meetings, we’ve got you covered!
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