Australia has witnessed the catastrophic effects of bushfires, from the 2009 Black Saturday bushfires to the more recent 2019/20 Black Summer bushfires which destroyed in excess of 3000 homes. Seeing the increasing effects of climate change, CSIRO scientists have predicted more frequent and intense fire seasons, furthering the need for bushfire-compliant homes.
To help protect buildings in the event of bushfire, special construction standards apply to bushfire-prone areas throughout Australia. Any home within a bushfire-prone area must now be built to achieve a BAL rating of 12.5 to help withstand ember attack.
Working with Prebuilt you can enjoy peace of mind knowing that all of our pre designed modular homes are built to a BAL 19 standard – with sealed roofs, sealing around windows, doors and screening windows, non-combustible cladding and steel frames.
How do I know if my property is in a bushfire prone area?
For Victorians, you can find out if your property is in a bushfire-prone area using VicPlan’s free planning property report tool. Simply enter your address and create a report.
For NSW you can visit the NSW Rural Fire Service website to see if your land is in a bushfire-prone area and if there are any planning overlays on your site.
What do I do if my home is in a bushfire prone area
If your modular home is in a bushfire prone area you are in safe hands. Prebuilt has delivered a wide variety of homes that comply with BAL ratings up to BAL 40, which is considered to be a very high risk home for bushfires. Our partner architects will work with you to ensure that your custom modular home meets all of the compliance requirements for your site’s rating. The first thing you need to do is organise a BAL assessment for your site.
An accredited bushfire consultant can provide a BAL report that will assess the Fire Danger Index, slope of the land, types of surrounding vegetation and proximity to any building. This report is required as part of your building permit application. It allows Prebuilt and partner architects to accurately and appropriately select materials to be able to build to the BAL ratings of each site.
What is a BAL Rating?
BAL is short for Bushfire Attack Level. In general, a BAL rating is a way to measures the potential for ember attacks, radiant heat and direct flame contact, as well as their severity. The BAL rating is measured in kW/m2 in accordance with the radiant heat increments.
There are six BAL classifications to determine the necessary building processes for the site. These classifications range from BAL low which means there is no requirement for bushfire compliant process up to BAL flame zone, which builds for the possibility of an ember attack and direct exposure to flames.
At Prebuilt, all our homes are designed to achieve a BAL rating of 19 as a minimum, and include steel frames as standard, at no extra cost to you. For BAL ratings that exceed this, all the way up until the BAL flame zone, you will need to factor in some additional costs for cladding upgrades, glazing upgrades, and other material upgrades.
View our mini guide to material changes as BAL rating increases.
What Materials are used to accommodate for BAL ratings?
Timber Cladding
Hardwood timber is an extremely durable material that can be used as cladding to achieve different design intent. It can be painted, stained or left to patina over time.
Prebuilt can use the following fire-resistant timbers on our projects: Spotted Gum, Blackbutt, Merbau, Silvertop Ash, Red Ironbark, and Red River Gum. These can be specified on our cladding, decks, and window frames depending on the BAL rating. All timber should be maintained with oil to withstand the elements.
Windows, Doors & Glazing
BAL 12.5 to BAL 29 require aluminium mesh screens to window opening, with BAL 40 to Flame Zone requiring steel mesh screens.
Glazing for various glass types and thicknesses can be found here. Where double glazing is used, the requirements apply to the outer pane only.
Building Steel Framing
Steel is a non combustible material, meaning it naturally does not catch fire. This makes it a durable option for the structure of your house with longevity beyond that of a timber frame structure. Prebuilt builds all homes using steel framing, which meets Victoria’s minimum Bushfire Attack Level of BAL 12.5.
What factors will affect a properties BAL rating?
Location
The access in and out of the property and the number of directions from which a bushfire can approach will have an impact on the BAL rating.
Vegetation
There are seven possible types of vegetation classified on a site which are known as; forest, woodland, shrubland, scrub, mallee/mulga, rainforest and grassland.
Keeping in mind that the density of vegetation impacts the intensity of the fire zone, as all vegetation can burn in extreme fire conditions. Other considerations are if there is a mixture of vegetation including leaf litter there may be an increased risk of a fire taking hold as smaller matter can be used as a kindling effect to enable the fire to migrate and grow.
Proximity to vegetation
Historically, the closer the property is to vegetation, the greater the fire risk.
Mapping research conducted by Professor John McAneney and Dr Kepin Chen in 2004 & 2010 found that since the 1967 Hobart bushfires 85% or more properties lost were within 100 metres of the bush and that there was no record of buildings built further than 700 meters from bushland destroyed by fire despite embers being able to exceed this distance.
Slope of the property
The slope influences the rate, severity and level of radiant heat flux when a bushfire occurs. Bushfires tend to move rapidly uphill rather than downhill.
The ‘slope’ is defined by the slope under the vegetation in relation to the building, not the slope between the vegetation and the site.
Follow this link to see how a slope is defined.
What is a Bushfire Management Overlay?
A bushfire management overlay (BMO) is a planning permit in Victoria that may be required for development. Its main purpose is to ensure that bushfire risk, management and protection has been considered.
What do I do if there is a Bushfire Management Overlay on my site?
If you are in an area of extreme bushfire hazard, it is likely that your property will be in a Bushfire Management Overlay (BMO) and your council’s planning scheme will apply to its development and use. You will need to engage an experienced consultant to complete the Bushfire Management Plan consisting of a Bushfire Hazard Landscape Assessment, Bushfire Hazard Site Assessment, Bushfire Attack Level (BAL), and a Bushfire Management Statement Report.
You can find an accredited bushfire planning and design practitioner to help with this process at the FPAA website.
What does a BAL 40 Bushfire home design look like?
Daylesford BAL 40 Home
Prebuilt’s Daylesford home showcases a typical response to a BAL 40 rating, where all external materials must be non-combustible. Subfloors are built to include a cement sheet underlay while windows and doors are metal with glazing upgrades and/or the inclusion of BAL 40 rated window shutters.
The ability to interchange the cladding throughout the façade means our clients do not need to compromise on sleek and sophisticated design when complying to a BAL 40 rating. Our Daylesford pergola was built without timber components, utilising steel for the outdoor structure and non-combustible outdoor flooring with a tiled finish.
Daylesford images by Inkdfotogrfa
View more images of the Daylesford BAL 40 home
Explore Options for Bushfire Proof House Designs
Bushfires are an unavoidable part of Australian rural living; this doesn’t mean you have to change your lifestyle choices to protect your home. Let our prefabricated design process prepare your home in the best possible way against the threat of a bushfire. Contact the team at Prebuilt today to discuss how we can assist with appropriate BAL rated homes.