Design defenses | Architecture & Design

Since the 1983 Ash Wednesday fires in South Australia and Victoria, CSIRO has surveyed every significant house loss to bush fires. Those 26 years of research, along with large-scale laboratory investigations into the performance of buildings under fire, have led to the reform of the Australian Fire Authorities Council (AFAC) and now form the basis of the fire and emergency services.

Over 90 per cent of all houses lost to Australian bushfires occur without flame and radiation from the fire front, CSIRO’s research found. Houses are often so susceptible to fire that embers or high heat alone will start a blaze.

While the Building Code of Australia (BCA) should provide a minimum temperature that homes must be able to withstand, the Australian Fire and Emergency Service Authorities Council (AFESAC) have criticised it for being too low. The fire temperature proposed in the draft national building code assumes that a bushfire has a temperature of 1,000 Kelvin (or 727 degrees Clesius) but, AFESAC claims, that temperature should be 1090 Kelvin (817 degrees Clesius). If approved next month, the lower 1,000 Kelvin model could be included in every state and territory building act.

But bushfire resistant design can be crucial in protecting homes from fires, the Fire Protection Association Australia (FPAA) claims. To beat the flames, architects can design to these principles:

Roofs

Should be pitched with a slope either side and the valley should be kept to a minimum. Timber shingles are not recommended, instead metal or fibre cement materials are recommended, or if the roof is tiled it should be fully sarked to prevent embers from entering.

Location

Don’t build on the top of hills or north-facing slopes. A minimum of 20-metres’ clearing is needed around a house if the adjacent woodland is at land level. For a five-degree slope, this rises to 25 metres; for 10 degrees, 34 metres; for 15 degrees, at least 57 metres plus the highest standard of bushfire resistant design.

Windows

Timber window frames should be treated with fire retardant. Windows should be toughened glass and leadlight windows should be covered with a sheet of toughened glass or non-combustible shutter.

LPG tanks

LPG tanks should ideally be installed away from the building. If an LPG tank is located next to your house, vents should face away from the property.

Walls

Timber should be fire retardant treated. PVC cladding should not be used. Gaps should be sealed.

Water tanks

You must ensure there is water in the tank, even if it involves purchasing water. Fire brigade fittings on tanks are advisable. A diesel pump for pumping water is necessary, to ensure the pump will still operate without electricity.

Bunkers

Should not be under the house.

While clever design can reduce the effect of fire it is important to remember that design alone will not save a property or a life. “In the event of a bushfire you must have a plan and know the correct procedures for protecting yourself and your property,” FPA Australia Technical Officer, and CFA Captain, Sharon Merritt said.

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