Bushfire construction requirements

This is general advice and may not apply specifically to your property. For more detailed information on your personal circumstances please contact the Rebuilding Planning Team on 9294 6999.

AS 3959 is the Australian Standard that applies to bushfire requirements when building properties in Victorian. 

As BAL ratings increase, the use of non-flammable materials and methods of construction becomes more important.

Ember risk

Embers can enter through gaps as small as two millimetres. It’s important that the products and materials used are high quality so there are no gaps or holes left through which embers can enter the roof space, walls or underfloor. At higher BAL ratings, both the underside of the roof as well as above the ceiling should be covered and sealed with non-flammable insulating blankets to minimise ember entry.

Glass and windows

Glass and windows become more expensive at higher BAL ratings (e.g. BAL 40 & BAL FZ), so think carefully during the design phase about where glass is going and whether you will use window fire shutters.

Materials

Manufacturers have developed a wide variety of building materials, products and systems of construction that are suited to building in bushfire prone areas. Your designer or builder can recommend products that best suit your needs.

Some common materials used for external cladding or primary construction include corrugated and other steel profiles, fibre cement sheet or moulded panels of the correct thickness, brick, cement, rammed earth, and some timbers in lower BAL categories. Fire resistant sarking, roof and wall insulation products and sealants are also available.

Piping

Plastic pipe may be exposed to heat and melt creating an entry point for embers. The construction standards regulate these materials at higher BAL levels.

Sprinklers

Fire sprinkler systems can be considered, but they do not replace the need for the basic construction to be suited to the level of bushfire risk. This is particularly the case for a new build where eliminating combustible materials from the exterior of the building will generally be more effective and cheaper than a sprinkler system.

There are a range of bushfire sprinkler systems that can be designed into the roof construction or retrofitted to an existing structure. Avoid any designs that can trap embers and other materials on the roof.

Shelters

Victorian planning and building requirements also allow landowners to construct a private bushfire shelter or bunker. The installation of a private bushfire shelter does not remove the need for the house to comply with all the other planning and building requirements.

Costs

At lower BAL ratings, there are no fundamental changes for materials and construction methods that go over and above a typical building project.

At higher BAL ratings (40 and FZ), glazing costs increase, as do costs if shutters or other methods are implemented. Siting your structure to achieve a lower BAL exposure can have a big impact on costs for windows and glazing.

The table below lists what construction requirements there are for subfloor, floor, external walls and external walls and external windows. BAL - LOW has no special construction requirements and is therefore not included in this table: