Bushfire attack levels

Building a new home in a bushfire Attack level (BAL) identified location.

Clients often ask us about bushfire attack levels/zones and how this might affect their build. In this blog we’ll cover off some of the key information you need to consider when looking to build in a bushfire rated location and how this might affect approvals process, build timings and budget.

Firstly, what is BAL or bushfire attack level?

A BAL or bushfire attack level is a means of measuring the severity of a buildings potential exposure to ember attack, radiant heat and direct flame contact. This is measured in increments of radiant heat and is traditionally expressed in kilowatts per square metre.

BAL ratings are the basis for identifying particular requirements for a build and consider a number of factors including; the area you live, distance from vegetation to your home, slope of the site and more.

There are 6 key bushfire attack level categories in accordance with the Australian standard - AS3959 Construction of buildings in bushfire prone areas. These categories can be seen in the graphic below (examples pasted in).

Bushfire attack levels
Bushfire attack levels

How does BAL affect my build?

There are a number of standards you must comply with based on your sites identified BAL rating. This will dictate aspects such as the home design, construction methods and also the materials used in the construction (among other considerations) and unfortunately, some of these aspects can have an influence on the cost of your build.

Some of these aspects include (but not limited to):

External Walls
From a BAL rating of 19 and upwards, external walls must be made from specific materials – namely, non-combustible material or bushfire resistant timber. For our Callala project which is in a BAL-FZ zone (the highest possible rating), the exterior walls utilise James Hardie Axon fibre cement cladding for its fire resistance and longevity.

Roofing
In the case of a BAL 40 rating, roofing materials need to be made of non-combustible materials such as steel. Where the BAL rating is 12.5 and up, roofs need to be fully sarked and the junction between the roof and walls must be completely sealed.

Penetrations through roofs or walls
When you have a higher BAL rating, you’ll need to take into account any openings that come through walls or the roof. This includes things like vents, extractor fans, and downpipes – all of which should be made from metal, rather than PVC to ensure they are more heat resistant.

Windows, shutters, and doors
Glass openings to your house, including windows and glass doors, can break during a bushfire from flying debris and heat. Thicker, toughened glass should be used along with frames made from materials that match the criteria of the BAL rating.
Tight-fitting window shutters can also be implemented to protect windows during bushfires. You can view an example of these in our Callala Beach Project in a BAL-FZ zone below.

Decks and under floors
Floors should be built low to the ground with a subfloor structure that is made from non-combustible materials. Decks should be made with non-combustible materials or bushfire-resistant timber, depending on the BAL rating.
Decks are built as standalone structures and not directly connected to the house – this ensures that in the case of them igniting that they can detach from the house as they burn rather than spreading fire into the main structure of the home.

Sealing gaps
All gaps between cladding and eaves, as well as doors and windows should be sealed to prevent embers from lodging in-between gaps and making the building catch fire. Sealing off these gaps also helps to create a more energy efficient home by preventing uncontrolled ventilation.

Rainwater tank for firefighting
In many bushfire prone areas the relevant fire authority in your area may require a water tank to be installed on site specifically for firefighters to access this water to defend homes when required. Fire fighting water tanks must be above ground, made from non-combustible materials and include a pump system suitable for fire fighting purposes.

More Information

If you want to find out more about building in a BAL area, here are some resources available online:

https://www.rfs.nsw.gov.au/plan-and-prepare/building-in-a-bush-fire-area
https://www.bushfireprone.com.au/faqs/

How we can help

Evolution Building Group specialise in design and construction within (list BAL levels EBG cover here) including;

  • approvals and planning: partner with local government and/or private certifiers to ensure that we are follow the appropriate approval pathway for your particular BAL
  • quality designers to ensure home designs meets and/or exceed all current BAL codes and practises
  • quality construction methods to ensure we meet and/or exceed all current BAL codes and practises
  • quality suppliers to ensure that their products are certified to meet and/or exceed BAL requirements
  • partnering with our clients to identify their BAL, what is required to ensure we not only meet the standard but also ensure the safety and structural integrity of new home and most importantly work within client budget

Evolution Building Group love to help people find their happy place. We hope this article has helped you understand more about what is inbolved in building a new home in a BAL location.

If you want to know more, we are here to help.

> Contact us via email, phone or come into our display home to discuss your questions.

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