Bushfire Prone Area Mapping in Victoria: BPA, BMO, BAL and AS 3959

What it is

Victoria runs two parallel bushfire controls for residential building. The Bushfire Prone Area (BPA) is a building control overlay shown on a state wide map. The Bushfire Management Overlay (BMO) is a planning scheme overlay applied to land of higher hazard. Land can be inside the BPA only, inside both the BPA and the BMO, or outside both. The two controls trigger different obligations and a builder needs to read both for any residential project on rural, peri urban or vegetated land.

Bushfire Prone Area

The Designated Bushfire Prone Area is the building control map gazetted by the Minister for Planning under section 192A of the Building Act 1993 (Vic) and clause 13.02 of the Victoria Planning Provisions. Properties inside the BPA are subject to the bushfire construction requirements of the National Construction Code (NCC) Volume Two, Part H7, which incorporates AS 3959 Construction of buildings in bushfire prone areas.

Any new home, addition or alteration that is a class 1, 2, 3 or associated class 10a building inside the BPA must be designed and built to a Bushfire Attack Level (BAL). The minimum applied across the BPA is BAL 12.5. Higher levels of BAL 19, BAL 29, BAL 40 and BAL FZ apply based on a site specific assessment of vegetation, slope and distance to the classified vegetation.

The BPA does not need a planning permit by itself, although other planning controls on the same land may still require one. The BPA is a building permit consideration enforced by the surveyor at building permit stage.

Bushfire Management Overlay

The BMO sits in clause 44.06 of the Victoria Planning Provisions. It applies to land considered to be at the highest bushfire risk and adds a planning permit trigger for most residential development. A permit is required to construct a building or carry out works for accommodation, including a dwelling, dependent person's unit, or extension that increases the floor area by more than 50 per cent.

A BMO application must address the bushfire planning provisions in clause 53.02. Clause 53.02 sets approved measures and bushfire objectives, including defendable space, water supply for fire fighting, access for emergency vehicles and a BAL of no greater than 29 unless the application meets the AMM2.2 exception in clause 53.02-5.

The clause distinguishes a single dwelling application from a settlement scale application. For a single dwelling, the application must address the bushfire objectives at clause 53.02-3, and meet the approved measures at clause 53.02-5 or demonstrate the alternative measures in clause 53.02-6.

BAL assessment under AS 3959

A BAL assessment is the engineering step that decides the construction requirements. AS 3959-2018 sets the method. Method 1 is a simplified procedure that uses site characteristics including the Fire Danger Index, classified vegetation, distance from vegetation and slope of land under the vegetation. Method 2 is a site specific bushfire attack assessment using radiant heat calculation.

The output is a BAL of LOW, BAL 12.5, BAL 19, BAL 29, BAL 40 or BAL FZ (Flame Zone). Each BAL has its own construction requirements in sections 5 to 9 of AS 3959, covering external walls, windows, doors, decks, roofs, sub floor spaces and gutters. BAL FZ requires construction for direct flame contact, which adds significant cost.

NCC referencing of AS 3959

The NCC adopts AS 3959 as the referenced standard for bushfire construction. NCC Volume Two Part H7 of the housing provisions requires that a class 1 building, an associated class 10a building or a deck attached to a class 1 building constructed in a bushfire prone area be designed and constructed in accordance with the BAL determined for the site.

The state appendix to the NCC for Victoria modifies how H7 applies, but the substantive AS 3959 obligation remains. Building surveyors check BAL evidence before issuing a building permit on a BPA site.

How the layers stack

A typical regional Victorian residential project sits inside the BPA only, with the BMO applying where vegetation hazard is highest. On a BPA only site, no planning permit is required for the bushfire control, but the building permit must satisfy AS 3959 and NCC H7. On a BMO site, a planning permit is required first, then the building permit. The planning permit conditions usually require a minimum BAL outcome and defendable space management, which the building permit and the long term occupation of the dwelling must maintain.

For builders pricing residential work in regional Victoria or peri urban Melbourne, run a Planning Property Report on the address before quoting. The report shows BPA status, BMO if applied, and the zone and other overlays. Carry the cost of the BAL assessment, the bushfire planning report if BMO applies, and the higher construction cost of the resulting BAL band in the early stage budget.