AS 3959 explained: the standard for building in bushfire-prone areas
AS 3959 is the Australian Standard for building in bushfire-prone areas. Its full title is AS 3959:2018 Construction of buildings in bushfire-prone areas. It does two jobs: it sets out how to work out a site's Bushfire Attack Level (BAL), and it says how a building has to be constructed for each level, from BAL-12.5 to BAL-FZ.
What AS 3959 covers
The standard has two halves.
The first explains how to determine a site's BAL. It covers how vegetation is classified, how distance and slope are measured, and the two methods for combining them. The result is one of six levels, from BAL-LOW to BAL-FZ. BAL levels explained describes each.
The second half sets out the construction requirements for each level. It goes element by element through the building: subfloors, floors, external walls, windows and doors, roofs, eaves, gutters, verandahs and decks, and services like water and gas pipes. The requirements get stricter as the level rises. Each level's guide summarises them in plain English: BAL-12.5, BAL-19, BAL-29, BAL-40 and BAL-FZ.
What AS 3959 doesn't cover
It's a construction standard, not a planning document. It doesn't decide which land is bushfire prone, whether you can subdivide, how wide a cleared area around the house must be, or what access and water supply a site needs. Those come from each state's planning rules, such as Planning for Bush Fire Protection in NSW, the Bushfire Management Overlay in Victoria and State Planning Policy 3.7 in WA. The BAL calculator by state links to each.
Method 1 and Method 2
AS 3959 has two ways to work out a BAL.
Method 1 is the simplified procedure most sites use. The assessor classifies the vegetation within 100 metres of the building, measures the distance to it and the slope of the ground under it, and reads the BAL from tables that also depend on the region's fire danger index. It's quick and repeatable, but it only works within set limits, for example on ground under the vegetation that isn't too steep.
Method 2 is a detailed calculation. Instead of tables, the assessor models the fire's behaviour and the radiant heat reaching the building, using site-specific inputs. It's used where Method 1 doesn't apply, such as very steep ground, or where a more site-specific answer could give a lower level. It's specialist work, normally done by an experienced bushfire practitioner.
BAL Buddy uses Method 1 only. How a BAL is worked out goes through it step by step.
How AS 3959 links to the National Construction Code
AS 3959 isn't law on its own. It becomes a requirement through the National Construction Code (NCC), which the states and territories adopt through their building laws. For houses and other residential buildings in a designated bushfire-prone area, the NCC's deemed-to-satisfy pathway is to build to AS 3959, or for steel-framed houses to the NASH Standard for steel framed construction in bushfire areas. A building can also comply through a performance solution designed by a specialist.
States can vary how the NCC applies. NSW is the main example: there, the NCC points to Planning for Bush Fire Protection as well as AS 3959, and a site's BAL is set using that document's own method. Victoria removed its rule that every new home in a bushfire prone area be built to at least BAL-12.5 from 1 May 2026.
Which edition is current?
AS 3959:2018 is the current edition, with amendments since it was published. Standards Australia says a revision has been through two rounds of public consultation and is in the final stages of development. When the new edition is published, the NCC and each state will decide when it starts to apply, so for a while you may see both in use. Your building surveyor will tell you which edition your project is assessed against.
Where to get AS 3959
AS 3959 is a paid, copyrighted standard. You can buy it from the Standards Australia store. Most homeowners don't need the full standard: your designer, builder and building surveyor work from it. For a plain-English guide, Standards Australia publishes a free Homeowner's Handbook (SA HB 208.2) on preparing and maintaining a home in a bushfire-prone area, alongside a practitioners' handbook (SA HB 208.1).
Checking your likely BAL
A BAL assessment under AS 3959 is done by a bushfire practitioner. Before you pay for one, BAL Buddy gives you an indicative BAL using Method 1, so you can see where your site is likely to land and how far the building would need to move for a lower level.
BAL Buddy gives an indicative Bushfire Attack Level (BAL) only. It isn't a determination under any Act, and no council or building surveyor has to accept it. For a BAL you can rely on, use an accredited bushfire practitioner.
Questions people ask
What is AS 3959?
The Australian Standard for construction of buildings in bushfire-prone areas. It sets out how to work out a site's Bushfire Attack Level and the construction requirements for each level.
Is AS 3959-2018 the current version?
Yes. AS 3959:2018 (with its amendments) is current. A revision is in the final stages, and your building surveyor will tell you which edition applies to your project.
What are the BAL construction requirements?
They're set out in AS 3959 for each level, element by element. In short, the lower levels focus on keeping embers out and the higher levels add heat-resistant glazing, non-combustible materials and, at BAL-40 and BAL-FZ, tested systems. Each level guide has a plain-English summary.
Is AS 3959 free?
No, it's sold by Standards Australia. The Homeowner's Handbook (SA HB 208.2) is free.
Does AS 3959 apply in NSW?
Yes, for construction. But in NSW a site's BAL is set using Planning for Bush Fire Protection, which has its own method and tables, so a NSW BAL can differ from a straight AS 3959 Method 1 result.