BAL 12.5 vs BAL 40 Materials: What You Can and Can’t Use for a Fire-Safe Home in WA

Bushfires, unfortunately, are a common occurrence in Western Australia. With rich vegetation and one of the driest climates in the country, our region has an environment that makes it easy for bushfires to ignite and spread. With 90% of WA deemed bushfire-prone, how do we ensure homes are built to safely protect their residents during such events? Ahead, we break down BAL ratings—specifically BAL 12.5 and BAL 40 requirements—and how materials and installation can differ across the levels.

What are BAL Ratings?

The Bushfire Attack Level (BAL) rating measures how severe a residential structure can be affected in the event of a bushfire. It takes into consideration the three main bushfire threats: ember attack, radiant heat, and direct flame contact. As risks are especially significant for WA homes, BAL ratings help ensure everyone’s homes are built to be fire-resistant and safe.

To determine your structure’s BAL rating, an assessor accredited by the Bushfire Planning and Design (BPAD) inspects your site. Your area’s Fire Danger Index is taken into consideration, as well as the following:

Slope: fire spreads faster uphill, so the surrounding slope of the land around the building is assessed
Proximity: the distance between other buildings and vegetation can affect how fast the fire spreads
Vegetation: the density of vegetation and its flammability are also considered, as they fuel the fire

BAL 12.5 vs BAL 40 Requirements & Risks

BAL ratings have an increasing degree of risk. Here’s a side-by-side comparison of BAL 12.5 vs BAL 40 and their varying levels of exposure to bushfire threats:

BAL 12.5 Risks	BAL 40 Risks
Considered low risk Small chance of radiant heat & ember attacks (below 12.5kW/m2)	Considered very high risk Increased exposure to ember attack, ignited windborne debris, and radiant heat (between 29kW/m2 and 40kW/m) Increased likelihood of exposure to the fire front flames

Your building’s BAL rating will dictate the construction materials and installation methods you can use, which will directly affect your design, plans, and budget. As your BAL rating increases, material choices will gradually become more restricted.

Given this, materials that may pass BAL 12.5 requirements might not be acceptable for BAL 40 requirements. Considered a low risk, BAL 12.5 construction requirements require minimal materials for basic fire resistance. Meanwhile, BAL 40 building materials will need to be more fire-resistant and follow specific installation instructions.

BAL 12.5 vs BAL 40 Building Materials

Below is a detailed guide to BAL 12.5 and BAL 40 requirements and allowed materials for the main parts of a home build based on Australian Standards 3959:2018.

Decking

BAL 12.5 Decking Requirements	BAL 40 Decking Requirements
No specific decking materials required for most decking boards If within 300 mm horizontally and 400 mm vertically from glazed elements (doors and windows), decking should be: Non-combustible bushfire-resisting timber or timber with a density above 750kg/m³	Decking boards should be: Non-combustible a cement sheet or a system compliant with AS1530.8.1

Cladding

BAL 12.5 Cladding Requirements	BAL 40 Cladding Requirements
No specific wall cladding material required above 400mm from the ground Within 400mm from the ground, cladding should be made from: non-combustible material Steel cement sheet 6mm and above or timber with a density above 750kg/m³	Cladding should be installed on sarked walls Cladding material should be made from: non-combustible material thick cement sheet (min. 9mm) Steel or a system conforming to AS1530.8.1.

Walls

BAL 12.5 Wall Requirements	BAL 40 Wall Requirements
No specific wall material required above 400mm from the ground Within 400mm from the ground, walls should be made from either: non-combustible material High-density timber	Required wall material should be made from non-combustible material (concrete, brick, etc.) at least 90mm thick

Insulation

BAL 12.5 Insulation Requirements	BAL 40 Insulation Requirements
No specific insulation material requirements for walls and underfloors, but non-combustible insulation material like glasswool is recommended If using sheet metal roofs, foil-backed insulation blankets can be used to help seal off the roof from potential ember attacks

Recommended BAL-rated Products for WA Homes

James Hardie Fibre Cement Cladding

When it comes to BAL-rated cladding, James Hardie’s products are always at the top of mind. Engineered from fibre cement, James Hardie cladding and flooring products offer the strength and fire resistance needed to withstand bushfire attacks. Offering up to BAL 40 cladding options, James Hardie fibre cement comes in a range of colours and finishes, allowing you to build bushfire-safe houses in style.

NewTechWood Composite Timber Decking & Cladding

Those who prefer a natural wood look for their cladding and decking can also opt for NewTechWood composite timber products. The innovative brand uses reclaimed timber reinforced by recycled plastic, making its cladding and decking weather-proof and resistant to fire, unlike regular timber materials.

Nasahi AAC Wall, Floor & Fencing Systems

For a fire-resistant home that’s BAL-compliant, Nasahi wall, floor, and fencing systems are highly recommended. Made from autoclaved aerated concrete or AAC, Nasahi’s products are lightweight, durable, and most importantly, non-combustible. A versatile material, AAC is a top choice for builders looking for BAL-rated materials in Perth that can be adapted to any application or design.

Siniat Fire-Rated Plasterboards

Lastly, if you’re looking for plasterboard to make BAL-compliant internal walls, Siniat Fireshield is a cost-effective option recommended for Perth homes. Unlike regular plasterboard, Siniat’s fire-rated plasterboard has high fire resistance that can help meet NCC requirements. When properly installed, Siniat Fireshield systems can achieve 30 to 240-minute Fire Resistance Levels, making them suitable for specific BAL-rated homes.

For a detailed list of recommended building materials that are BAL compliant, check out our blog here.

Ensure Your Building Plans are Compliant

Before proceeding with constructing houses, always consult with your assessors about specific requirements for your BAL rating. You can also check out the Government of Western Australia’s guide on building in bushfire zones or AS 3959:2018 for more information on full requirements and specifications for building BAL-rated homes.

Understanding the requirements beforehand will help streamline your construction process, avoiding costly retrofits or overhauls.

Get BAL-rated Building Materials You Can Trust

All set to build? Construct a home that is fire-safe by getting your building materials from suppliers you can trust. At Westgyp, the products we stock from brands like James Hardie, NewTechWood, and more have undergone testing to certify their performance in BAL-rated settings.

Contact us today to explore fire-resistant construction materials available for your build—whether it’s for meeting BAL 12.5 or BAL 40 requirements in WA, our expert staff are here to help.