- Functionality (such as provision of shade and protection from wind, screening of undesirable views and visual privacy),
- Suitability for the area,
- Drought resistance,
- Growth rate,
- Ability to support wildlife, and
- Appearance and character
Common Misconceptions
Another reason for lack of preparation for bushfires may be a number of misconceptions about buildings and bushfires. There seem to be several common misconceptions in circulation. Some of these could discourage people from doing anything to prepare, while others could lead them into doing the wrong thing (such as evacuating their house at the wrong time). Some of these misconceptions are listed below, together with their counter-facts.
Misconception 1
‘Bushfires are usually so severe that there is nothing you can do, and it is not worth the trouble and expense of preparing for them.’
Counter-fact 1
While many buildings are destroyed by bushfires, many others survive similar conditions, not just by chance but because all buildings perform in bushfire according to known scientific principles. Buildings and their surroundings can be designed according to these principles to improve greatly the chances of survival.
Misconception 2
‘The heat of the bushfires is so intense that buildings made in the usual way could not survive. Only a brick or concrete bunker could survive and I don’t want to live in that!’ Objects such as melted glass in the burnt remains of a building are taken as evidence to support this view.
Counter-fact 2
There is no denying that bushfires generate large amounts of heat and very high temperatures. However, in some cases such as the ‘melted glass’ it is the heat of the building itself burning that melts the glass, not the heat of the bushfire.
A building is usually a concentration of combustible fuel capable of sustaining an intense fire longer than the vegetation around it, except perhaps in some cases where the vegetation is a forest with a very heavy concentration of fuel.
Misconception 3
Many people understandably seem to have an intuitive belief, based on their limited experience with fire, that most things which catch fire are ignited by flame. This may lead to the belief that flames from the bushfire are the major threat.
Counter-fact 3
Research indicates that ignition of buildings is much more likely to be caused by wind-driven embers and other burning debris than by flames of the bushfire itself. These ignitions may be caused directly by embers and burning debris coming into contact with a combustible part of the building, or indirectly by embers and burning debris lodging in combustible litter or other debris and then igniting the building. Flame attack from the bushfire lasts only for several minutes during the passage of the fire front at the building. The attack of wind-driven burning debris may go on for hours, particularly after the fire front has passed, and embers will continue to be blown from piles of long-burning material and ashes.
Misconception 4
‘Buildings explode in bushfires.’
Counter-fact 4
There is no known scientific evidence to support the view that buildings suddenly explode due to the heat of the bushfire. The phenomenon reported as an explosion may be a ‘flashover’. Flashover occurs in an enclosed room when a stage is reached where combustible materials are heated sufficiently to produce flammable vapours. With additional air, such as may occur with the opening of a door or breaking of a window, the fire grows suddenly to give flames throughout the compartment. The fear that building may explode in a bushfire (except from known causes such as stored flammable liquid for example) could cause occupants to evacuate a building at the very time when conditions outside, from radiant heat especially, are such that they may be lethal, an it would be better for them to stay indoors longer.
Taken from ‘Landscape and building design for bushfire areas’ Caird Ramsay and Lisle Rudolph. CSIRO Publishing Australia