Sealing a roof in bushfire prone areas of Australia has never been more critical.
In recent years, the bushfire season is seen to start earlier in spring. And more extreme bush fire levels during the summer are occurring worldwide.
In just the last 12 months, recognised flame zone areas such as Queensland and New South Wales were impacted early in October 2023. By late January 2024, Western Australia started experiencing out of control bushfires.
As bushfire conditions in Australia increase in frequency and become more dangerous, protecting a building’s exposure to high levels of of radiant heat means paying close attention to roof penetration.
Specifically, roof pipe penetration and roof flashing.
In this article: you’ll find out the all-important BAL roof flashing types available at a trade plumbing suppliers. Each is specifically made to latest Australian standards AS1530.8.1-2018 to protect against bush fire ember attack, radiant heat and direct flame contact.
Jump here to see our BAL rated roof kits
What is BAL and What Are the Risks Involved?
BAL stands for Bushfire Attack Level.
This is a construction and building bushfire rating the Australian government applies to how prone a property is to the specific risks of:
- Ember attack – embers can be clusters of burning twigs, bark, moss or leaves carried by the wind. Fires can soon spread ahead of the front line of the main fire. This is the 2nd highest attack level which can ignite debris on roofs, in gutters and windowsills or under raised floors.
- Radiant heat – mostly rises up in the air. High levels also radiate through the air at ground level, travelling in all directions. When reaching a combustible material, it will smoulder and eventually burn.
- Direct flame contact – from the front line of the main fire it’s the highest attack level. Having burned through the vegetation flames bushfire flames now reach and make direct contact with a building.
Let’s now look more closely at each level of BAL …
BAL and radiant heat levels – what you need to know
An Aussie bushfire can generate escalating levels of radiant heat, which spreads quickly across wider areas of ground.
Combustible gases are created from the burned vegetation, will ignite when mixed with oxygen. Flames from the resulting fire can hit temperatures of around 1600°C.
Radiant heat from intense bushfire flames can spread to an area covering 100 kW/m2, compared to the sun at midday in summer reaching only 1 kW/m2.
There are 6 levels of bushfire attack
Each is rated by:
Radiant heat exposure – according to the extent of area covered, which is measured in kilowatts (kW) per square metre (sq m).
BAL LOW Under 12.5 kW per sq m
- Negligible risk of ember attack but the presence of any radiant heat exposure will be under 12.5kW per sq m.
- No added construction / modifications needed.
BAL 12.5 0 to 12.5 kW per sq m
- Low-risk, wind-ignited embers and burning debris with potential radiant heat maximum of 12.5kW per sq m.
BAL 19 12.5 to 19 kW per sq m
- Moderate but greater risk of ember attack, burning debris and radiant heat exposure up to 19 kW per sq m.
BAL 29 19 to 29 kW per sq m
- High-risk potential of ember attack, burning debris and radiant heat exposure, potentially reaching 29kW per sq m.
- Extensive building / modifications will be needed.
BAL 40 29 to 40 kW per sq m
- Very high risk level with expected ember attack, burning debris with direct exposure to flames and radiant heat up to 40kW per sq m.
BAL FZ 40 kW per sq m and flame contact
- Extremely high risk rating of ember attack, burning debris and direct exposure to flames. Identical radiant heat exposure risk of 40kW per sq m.
How to know if a property is at a high risk or low risk of BAL
If a property lies within a designated bushfire prone area, the basic way to determine if it’s at high risk or low risk of BAL is to carry out a bushfire attack level assessment.
Known as the ‘Simplified Procedure’, the BAL rating complies with Australian Standard 3959 Construction of Buildings in Bushfire-Prone Areas (including Amendments No. 1, 2 and 3).
How it works
The horizontal distance is measured:
- Between the external walls of the building and all nearby areas of bushfire prone vegetation including, trees, shrubs and unmanaged grasses. But not lawns, gardens or recreation parks.
A building will be HIGH risk if sited:
- Under 100 metres from bushfire prone vegetation
Here, bushfire attack roof flashing should be rated for protection up to BAL 40.
Or LOW risk if sited:
- More than 100 metres from bushfire prone vegetation
A property with little to no risk will be assessed as BAL-LOW (under 12.5 kW per sq m).
But a property under 12.5 kW per sq m – but with a level of low risk attached – will need bushfire rated flashing.
Protecting your roof with bushfire rated flashing
The roof of a building is often the first point of contact by burning embers carried by the wind.
A full range of BAL metal flash kits can securely protect roof pipes of all standard sizes and diameters from the highest levels of bushfire attack.
Under Australian Standards AS1530.8.1:2018 – a refinement of AS3959:2018 – compliance tests on building materials, components and structures are carried out at certified laboratories.
Australian Standards state: “Any roofing materials, systems or accessories shall be (a) non-combustible, and (b) sealed.
As bushfire attacks levels rise, BAL protection standards for components are also reinforced.
BAL 12.5 – Roofs
BAL 19
BAL 29
- Roof vents – must be fitted with ember guards of 2mm mesh or perforated sheet in corrosive resistant steel, bronze or aluminium.
BAL 12.5 – Water Pipes
BAL 19
BAL 29
- Above-ground, exposed water supply pipes – to be made from metal.
BAL 40 – Roofs
BAL FZ
Roof penetrations – including roof lights, roof ventilators, aerials, vent pipes
and supports for solar collectors must be adequately sealed at the roof to
prevent gaps greater than 3 mm. Materials used to seal the penetration shall be non-combustible.
In a nutshell …
We All Need to Be Aware and Prepared for Fire Hazards
Bushfires in Australia are arriving earlier in Spring, and with greater frequency and intensity.
Protecting a building’s exposure from escalating levels of of radiant heat often starts with guarding against roof pipe penetrations where airborne ignited embers collect.
Carrying out the ‘Simplified’ BAL Assessment will determine how prone a building is to attack and the BAL rating to be applied.
An increasingly recognised recommendation is to install roof flashing components certified with a BAL 40 rating, the second highest level of protection currently available.
FAQs
Q: What is the latest Australian Standards to comply with BAL protection?
A: AS1530.8.1:2018, which provides methods for determining the performance of external construction elements when exposed to radiant heat, burning embers and burning debris.
Q: Which states in Australia are exposed to the greatest risk to people and property?
A: While many of the severest bushfires occur in Victoria and New South Wales, the most exposed states are also in urban areas where homes and other buildings are nearby to flammable vegetation. Different states are at risk at different times of the year:
- New South Wales and S.Queensland – Spring to Mid-Summer
- S.Western Australia – Spring and Summer
- Southeast Australia – Summer and Autumn
- NW Western Australia and Northern Territory – Winter and Spring
Q: What’s the main difference between BAL 29 and BAL 40?
A: While both BAL 29 and BAL 40 are rated for increasing levels of ember attack, burning debris ignited by windborne embers, and increasing radiant heat, BAL 40 is rated for possible direct exposure to flames.
Ensure you select the right BAL rated flashpipe sizes
