Understanding Bushfire Attack Levels (BAL) in Victoria, Australia

Bushfires are a stark reality in Victoria, Australia, where dry landscapes and extreme weather create perfect conditions for devastating fires. To protect communities, the Bushfire Attack Level (BAL) rating system was introduced, ensuring buildings in high-risk areas are designed to resist bushfire threats. In this blog post, we’ll dive into what BAL ratings are, why and when they were implemented, and how they shape construction in Victoria, with visual aids to bring the topic to life.

What is a Bushfire Attack Level (BAL)?

A Bushfire Attack Level (BAL) is a standardized way to measure a building’s potential exposure to bushfire risks, including:

Ember attack: Burning particles carried by wind that can ignite structures.
Radiant heat: Intense heat from nearby flames that can damage buildings.
Direct flame contact: Flames directly touching or engulfing a structure.

The BAL system categorizes risk into six levels, each tied to specific construction requirements under the Australian Standard AS 3959-2009 (Construction of Buildings in Bushfire Prone Areas). These levels are:

BAL Rating	Risk Level	Description
BAL-LOW	Minimal	Insufficient risk to require specific construction measures, but ember attack is still possible.
BAL 12.5	Low	Significant ember attack risk, requiring basic protective measures like sealed roofs and windows.
BAL 19	Moderate	Increased ember attack and radiant heat, with burning debris possible.
BAL 29	High	Higher radiant heat and ember attack, needing more robust materials.
BAL 40	Very High	Flames may intermittently contact the building, requiring advanced fire-resistant designs.
BAL-FZ	Flame Zone	Building likely to be engulfed by flames, demanding the highest construction standards.

These ratings are determined by factors like the Fire Danger Index (FDI), land slope, and surrounding vegetation, which influence a bushfire’s intensity and spread.

The History of BAL Ratings

The BAL system was born out of tragedy. On February 7, 2009, Victoria experienced the Black Saturday bushfires, one of the worst natural disasters in Australian history. The fires claimed 173 lives, destroyed over 2,000 homes, and left communities reeling. The Victorian Bushfires Royal Commission, established to investigate the disaster, identified critical gaps in building regulations for bushfire-prone areas.

Key recommendations from the Commission included:

Designating Bushfire Prone Areas (BPAs) across Victoria to identify high-risk zones.
Implementing a standardized system to assess and mitigate bushfire risks for new constructions.

In response, the Victorian government introduced the BAL rating system, with BPA mapping first gazetted on September 7, 2011 (Bushfire Prone Area Mapping). These maps are updated regularly, with changes recorded as recently as September 10, 2024, to reflect new data on weather, topography, and vegetation. The BAL system ensures that buildings in BPAs meet minimum safety standards, starting at BAL 12.5, to withstand ember attack.

Why Were BAL Ratings Implemented?

The primary goal of BAL ratings is to save lives and protect property. Before 2009, Victoria lacked consistent building standards for bushfire-prone areas, leaving many homes vulnerable. The Black Saturday bushfires exposed this weakness, as many structures were unprepared for ember attack or radiant heat.

BAL ratings were implemented to:

Standardize construction: Provide clear guidelines for builders to follow in high-risk areas.
Enhance resilience: Ensure buildings can resist bushfire threats, from embers to direct flames.
Adapt to local risks: Tailor construction requirements to the specific bushfire hazards of each site.

By requiring all new homes in BPAs to meet at least BAL 12.5, the system ensures a baseline of protection, even in areas with lower immediate risk.

How BAL Ratings Shape Construction

Each BAL rating corresponds to specific construction requirements, designed to increase a building’s resilience. For example:

BAL-LOW: No mandatory measures, but general bushfire safety practices are encouraged.
BAL 12.5 to BAL 40: Increasingly stringent standards, including:
- Non-combustible materials for walls, roofs, and cladding.
- Ember-resistant screens on windows and vents.
- Sealed gaps around doors, windows, and eaves.
BAL-FZ: The most rigorous requirements, often involving:
- Fire-resistant structural elements.
- Specialized materials to withstand direct flame contact.
- Additional features like sprinklers or reinforced designs.

For instance, a home in a BAL 19 area might use double-glazed windows and non-combustible cladding, while a BAL-FZ structure could require fire shutters and concrete foundations. These measures are outlined in AS 3959-2009, ensuring consistency across Victoria.

Ongoing Management of BAL Ratings

The BAL system is dynamic, adapting to new scientific insights and environmental changes. The Victorian government is exploring ways to prescribe BAL levels based on the likely revegetated state of areas after bushfires, accounting for how regrowth can alter fire risks (Bushfire Prone Areas). This forward-thinking approach ensures that standards remain effective over time.

Additionally, the minimum BAL 12.5 requirement for all new homes in BPAs reflects a commitment to consistent safety, even in areas where the immediate risk is lower. Regular updates to BPA mapping, based on factors like weather and vegetation, keep the system relevant.

The Bushfire Attack Level (BAL) rating system is a cornerstone of Victoria’s efforts to protect communities from bushfires. Born from the lessons of the 2009 Black Saturday bushfires, BAL ratings ensure that buildings in bushfire-prone areas are constructed to withstand embers, heat, and flames. By setting clear standards and adapting to new risks, the system helps save lives and property. Whether you’re a homeowner, builder, or business like Vivid Skylights, understanding BAL ratings is essential for safety and compliance in Victoria’s fire-prone landscapes.

VIVID SKYLIGHTS HAS A BUSHFIRE ATTACK LEVEL RATING OF BAL – 29 Skylights may require additional accessories such as ember guards during installation, check with local building authority prior to installation depending on what BAL rating your site is.