AUSTRALIA’S national building code for constructing houses in bushfire-prone areas could only minimise the risk of people being killed or injured, not eliminate it altogether, the Black Saturday royal commission has been told.
“There is only so much the building code can do in this area,” the general manager of the Australian Building Codes Board, Ivan Donaldson, said.
“We are not dealing with absolutes. There are no absolutes here.
“This is about mitigating risk, about dealing with the risk. The notion that the ABCB, the building code (or) planning laws can eliminate the risk is another matter entirely.”
Mr Donaldson said the building code introduced by his board had never been promoted as offering a solution in its own right to the threat of bushfires and it was reasonable that the community “understand that risk exists”.
The inquiry into the Black Saturday bushfires, which killed 173 people and destroyed more than 2000 homes, was told earlier yesterday that shortfalls in the revised code for building in bushfire areas, hurriedly introduced after February 7, contained potentially fatal shortfalls.
CSIRO bushfire research scientist Justin Leonard said the revised standard did not cover the number of exits from a house or whether the exits led on to wooden decks or stairs.
That could leave occupants trapped because the only way out of a house that was on fire might be on to a burning deck or wooden staircase, which research showed were prime ignition points during bushfires.
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 3mm in outer walls, which would also allow embers to enter.
The revised standard for building in bushfire-prone areas, introduced in March, did not take into account other crucial factors, such as the siting of the house, water supplies, vegetation types and whether other easily combustible structures such as fences or sheds were placed nearby.
“A building standard isn’t particularly effective in isolation,” Mr Leonard said.
The building code was designed to protect a house only during the relatively short time it took for a firefront to pass, when in reality there was a “quite extended timeframe” 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 revised standard, which did not include bushfire factors such as ambient temperature, wind speeds, humidity and the moisture content of the materials.
The maximum flame temperatures used in the tests were also lower than those that could be expected in a firefront, and the new standard covered only buildings at risk from bushfires and not grassfires, Mr Leonard said.