Why This Matters Before You Design Anything

If any part of your block sits in a designated bushfire-prone area, your Bushfire Attack Level rating shapes what you can build, what materials you can use, and how much it will cost, often well before a designer draws a single wall. This guide explains how the system works in WA. It is general information only, not a substitute for a site-specific BAL assessment or advice from a registered building surveyor, since bushfire risk is a life-safety matter that always needs qualified, site-specific assessment.

How to Check If Your Block Is Bushfire-Prone

Before you do anything else, check whether your block falls within a designated bushfire-prone area using the Department of Fire and Emergency Services’ Map of Bush Fire Prone Areas, available through Landgate. If any part of your lot is shown in pink on the map, additional bushfire construction requirements apply to a new dwelling, extension, or associated structure like a garage or deck. A block located entirely outside a pink area isn’t required to comply, even if a neighbouring lot is affected, though it’s still worth checking with your local council directly since designations are reviewed periodically.

Understanding BAL Ratings: From Low to Flame Zone

A Bushfire Attack Level rating measures the severity of a building’s potential exposure to ember attack, radiant heat and direct flame, expressed as a heat flux in kilowatts per square metre. There are six ratings: BAL-LOW carries no specific construction requirements, BAL-12.5 and BAL-19 reflect low to moderate risk primarily from embers, BAL-29 and BAL-40 reflect high to very high risk with increasing radiant heat exposure, and BAL-FZ, Flame Zone, is the most severe rating and means direct exposure to flame is possible. Each rating above LOW triggers specific, increasingly strict construction requirements under AS 3959.

What a BAL Assessment Involves

A BAL assessment is a site-specific evaluation that considers the slope of your land, the type and density of surrounding vegetation, and how close that vegetation sits to your proposed building. It needs to be carried out by a suitably qualified assessor, and for anything beyond the simplest sites it’s worth using an FPAA-accredited Level 1 BAL Assessor or Level 2 Bushfire Planning Practitioner, since your building surveyor will rely on this assessment to determine what construction standard applies. It’s generally required as part of your building permit application if any part of your lot falls within a designated bushfire-prone area.

How BAL Affects Design and Construction Costs

Your BAL rating directly determines which construction requirements apply to almost every exposed part of the building: external walls, windows and doors, roofing, decking, subfloor enclosures, and even gutters and evaporative cooling units. At BAL-12.5 and BAL-19 this generally means non-combustible or ember-resistant detailing at manageable extra cost, while BAL-29 and above start requiring toughened glazing, metal window and door screens, non-combustible external walls, and sealed roof and vent penetrations, which add up quickly. At BAL-40 and BAL-FZ, construction requirements become substantially more expensive and design options narrow considerably, so it’s worth having an indicative BAL assessment done before you commit to a design that may not be achievable, or affordable, on that particular block.

Bushfire Management Plans and the Planning Stage

Under State Planning Policy 3.7, some developments in bushfire-prone areas need more than a BAL assessment at the building permit stage; they require a Bushfire Management Plan prepared and approved as part of the planning approval, generally triggered by a BAL-40 or BAL-FZ rating, vulnerable land uses, or where vegetation needs to be modified to bring the rating down. A Bushfire Management Plan is prepared by an accredited Level 2 or 3 Bushfire Planning Practitioner and, once approved, its recommendations need to be implemented and maintained for the life of the development, not just at construction. Check with your local council early, since this planning-stage requirement sits alongside, and is separate from, the building-stage BAL assessment.

Retrofitting and Renovating in a Bushfire-Prone Area

Bushfire construction requirements generally aren’t retrospective, so an existing home doesn’t automatically need to be upgraded if the area around it is later declared bushfire-prone. That changes once you’re doing building work: renovations or extensions valued over $20,000, or any work that increases the risk of ignition, will typically need to meet current requirements even on an established home. Below that threshold, sensible low-cost retrofits, ember guards on gutters and vents, metal window screens, sealing gaps around doors and enclosing exposed subfloors, meaningfully improve a home’s resilience even where they aren’t strictly mandated.

For the construction detail behind each BAL rating, our guides to windows, insulation and the building envelope and eco-friendly building materials cover many of the same building elements from a thermal-performance angle. Always confirm current requirements against the DFES bushfire-prone areas map and with a registered building surveyor before finalising a design.