How to best design your new home to minimise bushfire risk

Photo: The Department of Fire and Emergency Services
Photo: The Department of Fire and Emergency Services

ARCHITECTURAL design principles can minimise the risk to property and lives during a bushfire, according to Archicentre Australia.

“Engaging with an architect when planning a new home or additions to an existing residence ensures that sound design principles are incorporated to minimise the bushfire risk,” director Peter Georgiev said

“This means that the home can appropriately respond to the environment.”

While legislation was in place in most states to regulate construction in designated bushfire-prone areas, Mr Georgiev said there were always opportunities to design beyond these standards and specific to the environmental circumstance.

Archicentre Australia has a number of recommendations for people intending to build, rebuild or renovate a home in a bushfire-prone area.

Siting

“Houses should be sited to minimise the risk,” Mr Georgiev said.

“This may mean keeping away from steep hillsides where the intensity of the fire can double for each 10 degrees of slope, or ensuring enough cleared land is available between the house and the bush.

“The extent of required cleared land varies according to the type of vegetation in proximity to the proposed dwelling.”

Mr Georgiev said where the available building area was limited, design issues for bushfire-prone areas become paramount and expert advice was required.

House design

Mr Georgiev said all bushfire design principles seek to protect the home from burning debris.

“The key differences between bushfire design and traditional architectural design are that bushfire design uses a plan with a simple roofline, a minimum of angles and a range of fire-resistant alternative construction materials,” he said.

“Good design for bushfire-prone areas seeks to protect the house and its occupants from the five major dangers: wind, radiant heat, direct flame, ember attack and smoke.

“Principles such as simple rooflines, uncomplicated layouts, window protection, inbuilt water storage, fire-resistant materials where necessary and sprinkler systems can be integrated to achieve good protection as well as good design.”

Construction and materials

Mr Georgiev said houses were classified through Australian Standard AS3959 as being in low, medium, high or extreme bushfire attack areas, or as being in the flame zone.

“There are always sensible design precautions to be taken regardless of there being few, if any, statutory requirements; i.e. no requirements for the low category, and the flame zone category is always subject to separate assessment by authorities,” he said.

“By way of brief guidance, for the medium, high and extreme categories of bushfire attack, the National Constriction Code and AS3959 set out levels of acceptable construction.”

Mr Georgiev said non-combustible materials were generally acceptable, with the use of timber restricted to certain fire-tested species.

For floors, timber was acceptable in most categories, however if the floor was not enclosed, or for homes in the extreme category, it must be sheeted underneath with non-flammable material or constructed using fire-retardant treated timber.

Timber species that generally met the criteria included blackbutt, spotted gum, merbau, turpentine, red ironbark, red river gum and silvertop ash.

Mr Georgiev warned treated timber did not have any fire-retardant value and fumes from burnt treated timber could be toxic.

External doors must have weather strips or draught excluders and tight-fitting metal flyscreens.

In the high-risk category, aluminium mesh cannot be used and leadlight windows must be protected by non-combustible shutters or toughened glass.

In the extreme category, timber doors must be fire-retardant treated, have a non-combustible covering, be protected by non-combustible shutters or be solid core doors at least 35mm thick.

For the medium risk category, fascias may be timber but for the high risk category, fire-retardant treated timber must be used.

For decks, there must be a separation between timbers and the rest of the house to prevent the spread of fire into the building.

Landscaping

Landscaping features can slow the momentum of a bushfire.

“These include rivers, lakes, dams, swimming pools, irrigated or green summer crops, orchards, vegetable gardens, water-rich tree species, sporting ovals or tennis courts,” Mr Georgiev said.

“Some tree species, including native and imported species, have been classified as bushfire-resistant and can be used as wind breaks and barriers.”

Archicentre Australia has prepared a bushfire design guide available at www.archicentreaustralia.com.au/wp-content/uploads/Bushfire-Design-Guide.pdf.

In addition, the organisation recommends people check with the Department of Planning or their local council before starting any design work.