What You Need to Know About BAL-Rated Timber

For builders and trades working in bushfire-prone regions, choosing the right decking material is important for safety and compliance. While timber decking can pose a fire risk, there are a number of timber species that meet Bushfire Attack Level (BAL) standards, offering a balance of durability, performance and natural beauty.

This blog discusses BAL ratings, the timber decking options available and what to consider when installing decking in a bushfire-prone area.

Understanding BAL Ratings

A Bushfire Attack Level (BAL) rating measures the building’s exposure to bushfire conditions, including ember attack, radiant heat and direct flame contact. BAL ratings are determined during site classification and impact what building materials can be used in construction.

The BAL ratings includes:

BAL–LOW: Minimal risk. No special requirements for decking materials
BAL–12.5: Low risk from ember attack; materials should resist ember penetration
BAL–19: Moderate radiant heat; some timbers restricted
BAL–29: Moderate to high heat exposure; only BAL-tested and rated timbers permitted
BAL–40: High radiant heat and ember exposure; very limited timber use allowed
BAL–FZ (Flame Zone): Extreme conditions with direct flame contact; only non-combustible materials or tested systems may be used.

Understanding your project’s BAL rating is the first step in ensuring decking compliance under AS 3959: Construction of Buildings in Bushfire-Prone Areas. This Australian Standard sets the construction requirements, categorised by BAL ratings, to improve the building’s resistance against possible bushfires.

BAL-Rated Timber Species

Several durable Australian hardwood timbers have natural bushfire resistance and are approved for use up to BAL–29. Common timber species include:

Merbau; BAL 29
Blackbutt; BAL 29
QLD Spotted Gum; BAL 29

These species offer exceptional strength and aesthetic appeal, while meeting compliance requirements for many bushfire zones.

Decking Options for BAL–40 and Flame Zone (FZ) Areas

In higher BAL zones, traditional timber decking is typically unsuitable. Builders can instead consider non-combustible or composite alternatives, such as:

Fibre cement decking: Low maintenance and fully non-combustible
Aluminium decking systems: Durable, fire-safe and ideal for high-risk sites
BAL-rated composite decking: Composite decking is engineered to mimic a timber appearance with added fire resistance.

Installation Considerations in Bushfire Areas

Trade installing decking boards using correct spacing & ventilation.

Under AS 3959, correct installation is just as important as building material selection. Builders should pay attention to:

Board spacing: Limit gaps to prevent ember from entering the subdeck or subfloor
Fixing methods: Use compliant fasteners to ensure the deck remains in place longer
Subframe materials: Ensure supporting structures also meet BAL requirements to prevent the spread of the fire.

Follow the Australian Standards and the guidelines of the BAL area you’re working in to ensure compliance.

BAL-Rated Decking Solutions at Bowens

Bowens offers a wide range of BAL-rated decking options, including Merbau decking, Blackbutt timber decking, Spotted Gum decking, and White Mahogany decking.

For more guidance on BAL-rated building materials, feel free to contact your local Bowens store or drop by for a chat in one of our Melbourne or regional Victorian stores. For more products, explore our range of decking and decking screws to find the right product for the job.

Timber Decking in Bushfire Zones

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