Why Houses Burn Down
Homes burn in bushfires for one of the following reasons:
1. Flames and radiant heat from burning vegetation and other bushfire fuels too close to the home cause it to catch fire. Homes exposed to too much flames and radiant heat begin burning as the bushfire passes by.
Homes with too much vegetation close to them are difficult to protect from bushfires.
2. Burning embers collect on combustible surfaces or blow through cracks in a home's external cladding.
Embers begin falling before the fire reaches the home, and may continue falling for several hours after the fire has passed. Often homes only exposed to this 'ember attack' don't burn down until several hours after the fire has passed. If residents are there, homes can be defended successfully.
Well-prepared homes that are only subjected to ember attack can be defended by able-bodied people in most bushfires.
Unattended homes are three times more likely to burn down than homes that are actively defended.
Tasmania Fire Service recommends that you should not plan to defend your home when the fire danger rating exceeds 50 (severe) in your area unless you have created a defendable space and ember-proofed your home.
Tasmania Fire Service recommends that you should not plan to defend your home when the fire danger rating exceeds 75 (extreme) in your area unless your home has a defendable space and has been designed and built specifically to withstand a bushfire.
Exceptions to these rules are when firefighters have assessed (triaged) your home on the day a fire is threatening it, and have advised you that it may be defendable. This recognises that even on days with severe, extreme or catastrophic fire danger ratings, some well-prepared and constructed homes may be defendable due to their location. For example, a home surrounded by several hectares of ripening crops, ploughed fields or heavily-grazed paddocks may be safe to defend.