Last Updated Apr 12, 2017 · Written by Rob Schneider
Cyclones are low pressure systems that produce high winds and heavy rainfall. In Australia, they primarily occur in Queensland, the Northern Territory and Western Australia. Before 1985, standards were not introduced to prevent damage to homes in cyclones. Since more stringent standards were adopted, far less damage has happened to newer houses built to cyclone standards, but many homes are still in danger.
According to the Cyclone Testing Station, Category C cyclones occur in Queensland, the Northern Territory and Western Australia. A Category C cyclone has wind speeds of up to 252 kilometers per hour (km/hr). Category D cyclones have wind speeds of up to 317km/hr. Category D cyclones occur mainly in a coastal area of Western Australia.
Wind is not the only thing to worry about. Heavy rains cause flooding and storm surges in coastal areas can create giant tidal movements that flood coastal areas. A house must be built to sustain high winds, flooding and storm surges to be cyclone-proof.
A truly cyclone proof house will be built from the ground up to withstand cyclones:
Home footings and foundations must be set to a recommended depth and weight to avoid collapse.
Waterproof seals and water-resilient cladding prevents moisture from entering the home.
Doors must be reinforced with barrel bolts.
Windows should be made from shatterproof glass. Shutters and mesh screens are also recommended.
Guttering must be securely fastened to the house.
Roofing that is angled on four sides resists cyclones best. Roofing materials must be screwed or clipped down. Nails easily rip out during a cyclone.
Vents in the roof or eaves can reduce wind pressure if a door or wall fails.
Trees should be planted well away from the home. Trees fall in cyclones and can destroy a roof.
Wind speeds in Category C areas are measured in increments:
C1 equals wind speeds of up to 180km/hr
C2 wind speeds are up to 220km/hr
C3 equals up to 266km/hr
C4 equals up to 310km/hr
If you comply with minimum standards, you may face a more severe cyclone and your home won't be able to withstand the force of the wind. It's better to expect the worst and build a home that will withstand higher wind speeds.
Even if your home complies with standards, you need to keep it maintained. Studies of homes damaged by cyclones have revealed several causes related to maintenance issues. Even minor maintenance oversights can have a snowball effect and create greater damage.
Rusty fastening are a major cause of damage from cyclones. Look in the ceiling cavity and around the house for signs of rust. If metal roof coverings, battens, batten straps, bolts, fixing plates, screws, nails or other metal fixtures or fastenings are rusty, replace them. Rust can't stand up to cyclonic winds and downpours can lead to severe leaking through rusty roofs.
Untreated timber can rot. Termite damage, too, weakens timber. Both of these will make fastenings easily tear out during cyclonic winds. Look for rotten timber and termite damage. Replace rotten timber and have your home treated for termites. Replace termite damaged timber.
In tropical climates, timber will expand and contract. This is normal, but continual expansion and contraction will loosen fixings. Look for any loose fixings and tighten them. You may also want to add extra fixings to be sure your house is safe.
If you have an older home, you can take precautions to minimise damage to your home.
The main cause of damage is damage to the roof. Even partial damage to a roof can be catastrophic because the combination of high winds and torrential rains will damage the inside of your home. You may need to have a local builder inspect your roof and upgrade it to conform to the more stringent standards put in place after 1985.
Some of the things the builder might do include inspecting and fixing:
Roof sheet and batten connections
Batten to truss or rafter connections
Truss or rafter connections to wall connections
High winds will find any weakness in your roof. All roof connections should be firmly fixed to minimise the chance of roof damage.
Gables are subject to tremendous forces during a cyclone. The wider your gables are, the more force they will have to endure. Gables may not stand up to cyclonic winds. While your builder fixes your roof, they should also inspect your gables and reinforce them. They should have extra bracing and anchoring to withstand cyclonic winds.
Doors and windows, too, are vulnerable in high winds. If you have standard doors, have them reinforced with barrel bolts. If you have standard windows, replace them with windows that won't shatter. You can also buy impact resistant screens to protect your windows and shutters will give you extra protection.
Garage doors can sustain damage during a cyclone. Garage doors cover a wide area and cyclonic winds can push them in or suck them out. This can cause further damage to the interior of the garage. If your garage is attached to your home, the damage can extend to your home interior.
Any home attachments such as patio roofs, carports and other attachments can be lifted and carried by high winds. They can easily damage your home or even a neighbouring property. A good builder with knowledge of local weather conditions can reinforce them so they won't fly away during heavy winds.
Even flashings can lift. If they aren't torn off the roof, they can allow water to leak into your home. According to the Cyclone Testing Station, loose flashings are a major contributor to home damage. Make sure all flashings are installed for cyclonic conditions.
Almost anything left outdoors can create damage during a cyclone. Outdoor furniture, satellite dishes, solar panels, antennas and other outdoor items can become like missiles in high winds and damage your home or even fly into a neighbouring property.
Not to be underrated is leakage. In a cyclone, heavy rain combined with high winds can find its way into your home. Wind driven water can damage your walls, ceilings and carpets. The water can find its way through any gap in the roof, windows, doors or vents. Wherever there is a chance of leakage, you should fill the gaps to minimise the risk to your home interior.
We've covered most of the basics you need to know about cyclones, but more information is available. To find out more about cyclones and steps you can take to protect your home, visit James Cook University Cyclone Testing Station. The website includes a pamphlet for homeowners and a video. The more you learn about cyclones, the more prepared you will be.
It will cost money to cyclone proof your home, but the cost will be far less than the cost of damage to your home. The money you spend on your roof alone may save you from having to replace your roof and repair the damage caused to your home interior.