How Easily Can A Roof Blow Away?
When Mother Nature is not in a good mood, storms happen!
During storm season the news is filled with dozens of cases of houses losing their roofing or suffering any other damages. You might even start wondering just how easily this could happen to your own home. Well, we have all the answers for the questions you might have!
What happens to my roof during a storm?
The flow of air changes the moment wind hits a building. When it blows over the roof of a house, the wind forms vortices. Because of the suction that this creates, the roof is easily lifted up. In addition, if a window or door is broken by debris during the storm, the air that blows inside creates a huge pressure.
Due to the pressure inside and the suction outside, the roof is blown away. Of course, the outcome largely depends on the strength of the wind, the material and style of the roofing, the height of the roof or the position of the house.
For example, a nearly flat roof will suffer larger uplift forces than those that have a pitched shape. This does not mean that it’s impossible for a certain shaped roof to be blown away. Before you start panicking, you should consult a professional about how would your roof fare in such kind of a situation.
Which areas are affected the most?
Severe storms can occur in any part of Australia. The Great Dividing Range in Eastern Australia is the most hail prone area in the region. The most cyclone-prone region is an approximately 50km wide coastal strip of the Northern territory, mostly Queensland, and a 50km wide coastal strip of Western Australia and some parts of the inland as well.
These areas are only affected in the time period between November and April. The strongest winds are always detected in the coastal area of Western Australia. They can reach even a whopping 317 km/hr! Of course the stronger the cyclone is, the higher is the chance that your house might suffer damage. A category 3 cyclone has gusts that blow 170-227 km/hr, here the roof and structure of older houses might get damaged.
A category 4 cyclone (225-280 km/hr) can cause severe roofing loss and damage to the structure of old houses. A category 5 cyclone, with winds reaching the speed of 280 km/hr and above, causes widespread destruction. South and South-Eastern Australia fall under the normal category of areas to be hit by cyclones or storms while intermediate storm levels are felt from Brisbane to Cairns.
Unfortunately, severe weather can happen anywhere on the continent, so even if you do not live in the above-mentioned regions, you should still be prepared.
What kind of buildings are in danger?
Old houses tend to suffer the most when there are storms. It might be because the materials used during their construction have lost their strength with age, or they were not up to standards to begin with. Those houses that have been built before 1985 should be checked in any region of the continent, especially in areas that are threatened by severe weather. These buildings might not be built with materials up to standard, so they will be prone to damage during a cyclone.
Their roof connections might not be strong enough to withstand the wind. Even if they are newly built houses, they still might suffer damage. When a super cell storm hit Canberra in 2007, a newly built shopping centre’s roof collapsed due to the weight of the ice that fell on it.
Are there any laws I should pay attention to?
In Australia every house is wind classified, so you should check the documentation you have at home. Buildings in the areas that are under the threat of cyclones should always be built stronger than those that are not.
This means that, for example, houses built on a hill are in more in danger than those that are built on flat terrain since they are shielded by neighbouring buildings. But if a house is standing by itself on a large, flat terrain, it is exposed to danger, too.
You should contact your local council in order to determine the classification. Also, checking the condition of the building is a must if you want it to withstand strong gusts of wind. If your fasteners and roof battens are rusted, they should be changed immediately. Rotten timber can also cause the roof to suffer damaged during storms.
Local authorities will most likely force you to make modifications to your roof if it’s not up to standards. After the damaged caused by Cyclone Tracy in 1974, residents of cyclone prone areas are obligated to attach the cladding on buildings, and also have the roofs tied to the foundations.
Who should I contact?
While you might think that it’s cheaper for you to check the condition of your roof by yourself, professional help is advised. Professionals tend to find damage even where you think that everything is all right. The specialists we recommend to you are:
- A building certifier
- A structural engineer
- An architect
- A builder
- Roof restoration professionals
Any of these specialists might help you with assessing the condition of your roof. They can advise you what parts of the roof needs to be changed or repaired so that you will be prepared for the next storm. If you are still adamant on checking it yourself, you have to pay attention to these parts:
- Roof sheet-to-batten connections
- Batten-to-truss or rafter connections
- Truss or rafter-to-wall connections
- Tile connections
Am I protected if I take these advice?
All in all, your roof will have a higher chance of survival if you take the advice given here. Of course, there is no cyclone-proof house or roof. Regardless of the shape of your roof, the material it’s made of, or even the position of your house, if a really strong cyclone comes, it might not be enough.
The forces of nature tend to surprise us, but this does not mean that we should not try to be prepared for everything. Even if some parts of your roof suffer damage, it might be lesser than what it could’ve initially suffered. Surveys have shown that those roofs built as per relevant Australian Standards’ recommendations receive less damage during cyclones.
Constant maintenance and professional consultation will certainly help you in the future, be sure to do check-ups before and after cyclone season!