Poor building code ‘put people at risk’ from bushfires
26 August 2009
published by www.theaustralian.news.com.au
Australia — Shortfalls in the new national building code for new houses in bushfire prone areas left occupants potentially at risk, the Black Saturday royal commission was told today.
CSIRO bushfire research scientist Justin Leonard said the new standard, hastily introduced after February 7, did not cover the number of exits from a house or whether the exits led on to wooden decks or stairs.
This could leave occupants trapped because the only way out of a house was on to a burning deck or wooden stair case.
Mr Leonard said other shortfalls included no provision for enclosing sub floor spaces, which were particularly vulnerable to ember attack, and allowing gaps of up to three millimetres in outer walls, which would also allow burning embers to enter.
The new Australian standard for building in bushfire prone areas, introduced in March, also did not take into account other crucial factors, such as the siting of the house, water supplies, surrounding vegetation types and whether other easily combustible structures such as fences or sheds were placed nearby.
A building standard isnt particularly effective in isolation, Mr Leonard told the inquiry into the Black Saturday fires, which killed 173 people and destroyed more than 2000 homes.
The building code was also designed to only protect a house during the relatively short time it took for a fire front to pass, when in reality there was a quite extended time frame when occupants might be at risk if they went outside.
Mr Leonard was critical of the methods used to test the combustibility of building materials under the new code, which did not include bushfire factors such as ambient temperature, wind speeds, humidity and the moisture content of the materials.
The maximum temperatures used in the tests were also lower than those that could be expected in a major fire front.
And the new standard only covered buildings at risk from bushfires and not grassfires, Mr Leonard said.
Surveys conducted after previous bushfires found the most common ignition points in houses during bushfires were timber decks, timber facia boards, timber window and door frames and timber stairs.
Mr Leonard said there was no evidence that houses spontaneously exploded during bushfires. Rather they caught fire and slowly burning material inside the house gave off combustible gases, which eventually exploded.
The weather conditions that increased bushfire risk also made houses more likely to burn, as low humidity and high temperatures dried out the materials used in the structures, he said.
Mr Leonard said he was not opposed to backyard bushfire bunkers, but they would have to be carefully sited, have adequate air supplies and people would need to be educated in their safe use.