Keep your roof on this cyclone season

Cyclonic winds can batter a house with uplift forces at a typical roof truss connection equivalent to the weight of a car, which is good reason for homeowners to ensure their dwellings are up to scratch for the cyclone season, says David Henderson, the manager of James Cook University's (JCU) Cyclone Testing Station.

"During a cyclone, your house is not only being pushed sideways but is also being lifted up by its roofing," Henderson said. "These high-uplift forces are transferred down through the roof fixings to the battens, then to the truss or rafters and into the walls and down to the foundations."

Henderson said new homebuyers should be aware of the building standards applicable in cyclone-prone areas. He said existing homes should be inspected regularly to ensure they would stand up to winds of 250 km/h, which was what could be expected during a category 4 cyclone.

"Everyone gets regular servicing on a car. Typically, a home is our largest investment and does require ongoing maintenance. "If you are replacing your roof then the batten, rafter and wall connections should also be upgraded." Henderson said building certifiers, such as those at city councils, could provide detailed inspections and advice for the homeowner or homebuyer.

"Part of the work of the Cyclone Testing Station involves post-disaster investigations after cyclones and severe thunderstorms and we see the unnecessary damage that occurs when houses and properties aren't properly prepared for cyclones," Henderson said. "Things such as cladding, timber and garden sheds really can become airborne missiles. They can break a window resulting in large pressures inside the house which greatly increases the load needed to be resisted by the structure and increases the probability of failure."

JCU's Cyclone Testing Station is a world leader in engineering research into the wind effects on low-rise structures such as houses, stadiums and bulk-storage and industrial buildings. The Station is collaborating with the Bureau of Meteorology and the Queensland Department of Emergency Services in making an extensive assessment of the likely damage to coastal communities from severe cyclonic winds.

Over the past 30 years, the Station has conducted post-cyclone damage investigations both in Australia and overseas as well as broken new ground in testing cladding fatigue, roof truss hold against high wind uplift, corrosion of roof fixings and wind driven debris damage criteria. Many of the research findings are incorporated into Australian and international building standards and codes of practice.