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What’s a Wind Rating and Does My Home Have One?

30 September 2020

As like everything else in 2020, this year continues to throw curveballs our way as we prepare for the increased likelihood of a La Niña weather event majorly impacting the Northern and Eastern areas of the Australian continent. As of Tuesday, 29 September 2020 the Bureau of Meteorology have now advised that we are in a La Niña weather event and this will likely be ongoing until April, 2021.  Weather patterns like this that see the increased likelihood of cyclones, rain events and strong winds serve as a poignant reminder about the necessity and importance of understanding wind ratings.

As a brief introduction, all modern homes constructed post 1980’s have a wind rating. The wind rating is dependent on where your home is located, the topography of the area, the built environment surrounding it and the speed and likelihood of wind gusts expected in bad weather. This rating is the cornerstone of your home’s engineering and ensures it meets the Building Code of Australia.

South-East Queensland is located within a Zone (or Region) B; Non-Cyclonic region. The following categories are the most commonly used system to provide a wind rating on properties in South-East Queensland:

  • N2 Wind gusts of up to 120 kph – Predominately built up urban areas less exposed to high winds. Think Paddington, Bardon or Red Hill in the protected valleys and flats.
  • N3 Wind gusts of up to 150 kph – Urban fringe areas, coastal areas and exposed ridges. Think Moreton Bay, Ipswich, Logan and higher parts of inner Brisbane.
  • N4 Wind gusts of up to 180 kph – Highly exposed escarpments subject to severe updraughts. Think Mt Tamborine, Mt Glorious and Toowoomba Range.

Most homes in South-East Queensland fall into the N2 and N3 categories – however, there are some outlying suburbs that fall into N4. These numbers can be located on your home building or architectural plans.

In Central and Northern Queensland, these wind ratings play a vital role in mitigating and minimising damage caused by tropical cyclones. In cyclonic conditions, wind can apply inward pressure and outward suction to different external surfaces of a home. It places pressure on the wall facing the wind (windward wall) and suction on all other walls and the roof. Wind pressure tends to push the windward wall into the home, while suction tends to pull the other walls and roof outwards and upwards. These pressures act directly on the external cladding materials and are transferred by nails, screws or bolts to the structural elements underneath them.

Obviously, the likelihood of cyclonic winds are traditionally significantly reduced in South-East Queensland, however that does not exclude our region from experiencing sporadic wind events. In 2019, as part of an insurance repair allocation, our office attended a property in Peachester at the edge of the Sunshine Coast Hinterland after wind gusts reached 100km/h – completely severing the insured’s pool shade sail and lifting their cemented-in Hills Hoist straight out of the ground.

As licensed builders and preferred insurance repairers, it’s our business to know the Building Code of Australia and to ensure our works comply with all Australian codes and standards. Poorly performed remedial works that include poor wind rating compliance put you and your home at risk during storm season. As mentioned, with La Niña now upon us, the importance of correct wind ratings is now more important than ever to ensure the strength and durability of your home to withstand extreme conditions – and being Queenslanders, we know ‘extreme conditions’ all too well.

By Jason Russ

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