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what is a BAL rating



When starting on the journey of getting a new home – particularly in bushfire prone areas of Australia – at some point you’ll end up discussing the risk to the home of a bushfire. And in recent years, especially since Black Saturday February 2009, the term BAL Rating is used to rate this risk. So what is a BAL Rating?!


First up, BAL stands for Bushfire Attack Level. So a BAL Rating is a grade or ranking of how the house is going to be affected in a bushfire attack – high or low on a particular scale. Fairly straightforward, but let’s talk technical for a few minutes to help you understand the core principles that the rating is built on.


The unprecedented loss of life in the 2009 fires caused the authorities to substantially re-think things. Amongst them was housing design, and what became clear was that it wasn’t just the flames that were the problem, it was the embers jumping ahead of the flames – sometimes a long way ahead – that caused so many houses to be lost to the fire, which then continued to feed the fire.


So a BAL Rating is an assessment of the extent to which embers get inside your home and start a fire – it’s really as simple as that. Flames are dangerous, yes, but when it comes to house design, it’s ember attack that is sometimes more important.


The other key tenet in the rating is the location of the home. This may seem obvious, but there’s a few aspects to it that make it a bit trickier in practice –

1. The 30,000 foot view. Is the new home going to be in a region that has a lot of forest or woodland? Or is it in generally open country? Ok, bushfires can really start anywhere, but there are certain areas that are much more prone to bushfires due to the large amount of fuel. Land in these areas often have a planning overlay placed on them by the government that requires the owner to get special approval from the fire authority before building.

2. The localised view. Are there lots of trees nearby? Even though you might be in generally open country, there may be a plantation nearby which can pose a risk to the immediate vicinity. Anything within 100metres of the edge of the new home must be carefully classified as to whether it poses a risk. There are different levels of fuel (trees, woodland, shrubs, etc) and there’s a list of exemptions such as managed gardens, wind breaks, small clumps of trees that are apart from other trees, etc.

3. The gradient of the land around the home. Fire travels uphill a lot faster than it goes downhill – the opposite to most things. In fact, let’s put it another way, a bushfire can go right up a very steep hill in mere seconds, but a steep descent the other side can sometimes be enough to stop the fire. So if you’re building uphill from the source of a fire, such as a plantation or forest, then the risk increases – the steeper the gradient, the greater the risk.


So the authorities developed a scale. It’s all in the Australian Standard AS3959-2009. Here’s a brief overview of the scale with some of the wording taken directly from a table in the Standard –

  • BAL LOW. There’s insufficient risk to warrant any specific construction requirements on the home. Mostly only applies to sites in urban areas.
  • BAL 12.5. Technically, this means there’s less than 12.5 kW/m2 heat flux exposure to the home within 100 mtrs from vegetation, and is all about ember attack alone. Most of regional Victoria is automatically classified as BAL 12.5.
  • BAL 19. From 12.5 to 19 on the heat flux index, but with increasing levels of ember attack and even burning debris ignited by windborne embers.
  • BAL 29. Basically the same situation as BAL 19, but just getting higher on the heat flux index.
  • BAL 40. Getting more serious – this is like a BAL 29, but with the increased likelihood of exposure to flames along with an even greater heat flux.
  • BAL FZ. This stands for Flame Zone and includes the direct exposure to flames from a fire front in addition to heat flux and ember attack. Bad news, and almost impossible to build a home for this scenario.


But what does all of this mean for the home itself? A lot! There’s 2 things – how and where embers can get in, and the properties of the materials that these embers – or in the case of BAL 40 and BAL FZ, the flames – land on.


There are many things around the outside of the home that this affects, but here’s a brief list of the main items. Bear in mind that the impact on the home increases as the rating goes up, and one thing that’s become obvious is that it increases exponentially. This means that the impact from BAL 12.5 to 19 wont be the same as from BAL 19 to 29, etc – it jumps up exponentially each step.

  • Joins. This includes where the roofing overlaps the gutter. And any flashings or capping overlap the roofing. And where the windows meet the cladding or bricks. And where the eaves sheet meets the fascia. Etc. Any joins are to be minimised to prevent embers getting in. This item has affected the construction of homes in bushfire areas the most.
  • Windows. Depending on the rating, this can be affected minimally to dramatically, including the glass type and thickness, the material the frames are made out of and even the flyscreens.
  • Cladding. An obvious one, but when using weatherboard instead of brick there are things that need to be changed for the higher ratings. And also the concept of preventing embers entering at any point.
  • External Doors. Similar situation to the windows, this requires changes for the higher ratings such as being made from fire-resisting timber and the glass type.
  • Verandahs and decks. This can be a big one for BAL 29 upwards, and it can include significant changes – and costs – to get the verandahs and decking to comply. In fact, in the very high ratings, decks and verandah may have to be considerably reduced or even eliminated for the home to meet the requirements.
  • There are other sundry items such as exposed plumbing pipes, balustrading, and even garage doors.


Something we want to say at this point in the blog – we believe that the BAL Rating Standard isn’t just some government initiative to mitigate their exposure to law suits – it’s a real and valid requirement that will help save a home and its occupants in a bushfire.


We’ve heard people argue against it and say it doesn’t work. We’re not here to try and validate something the government has done, but we’ve personally heard stories of the way homes just ignited well ahead of the fire front, and anything that is done to mitigate those pesky embers getting in is only going to help. There’s no perfect system, and we’re not saying it will definitely save the house, but we’re saying it will help save the house. Don’t throw the baby out with the bathwater!


So when you’re working through the process of getting a new home, at some point, someone will visit the site to conduct a BAL assessment, and then create a report that shows that assessment. That report is then signed, and when everything’s submitted to the building surveyor for the building permit, they check this and either accept or reject it – at which point it gets amended as needed.


Most builders will have a way of identifying a likely rating early on in the process and can base their scope of works and pricing around this while the final rating is being determined.


There are additional costs associated with building in higher BAL Ratings, but that’s another story for another day!


As always, feel free to reach out for more information.
Disclaimer. This blog is our opinion only. The information provided in our blogs is accurate and true to the best of our knowledge, but there may be omissions, errors or mistakes. The information presented in our blogs is for informational purposes only and we are not professionals, so the content we provide shouldn’t be taken as legal advice. We strongly recommend consulting with a professional before taking any sort of action. We reserve the right to change how we manage our blog and we may change the focus or content at any time.

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