A Chat with a Bushfire Hazard Consultant – Part 2

Bushfire Hazard Consultant

Continuing our chat, and discussion with Bernie Trembath from Queensland Bushfire Planning about the role of the Bushfire Hazard Consultant in a renovation project.

If you haven’t already, Check out Part One here 

Have you seen our video chat? If not, or if you want to check it out again…Watch the video here

In this part we will cover, topics like ‘How the Bushfire Overlay works’, ‘Where the Bushfire Overlay applies’, ‘Things you should consider if you are in the Bushfire Overlay’ and much, much more..

So with no further adue…


Our chat with Bernie continues

How does the Bushfire Overlay Work

BT    Brisbane City Council, along with every other local authority is now obliged under the State Planning Act to actually address natural hazards, and by that I mean,  flood, significant landscape vegetation and particularly bushfire. All local authorities have actually mapped the bushfires within their local area. So if you look at the map, the bushfire categories will normally show up as a high, medium or low rating. So you look at that particular map and particularly look at where your block is actually located.

For the record, most local authorities have the interactive map and you can actually go there and have a look for yourself.

So let’s take Brisbane City Council for example.. It will just have a high, medium and low rating. Understanding that these are very broad brush ratings. So where the Council map says there is a particular hazard doesn’t necessarily mean it exists and the Council says that within its City Plan that it needs to be ‘ground truth’ to determine that the actual hazard does or does not exist. 


Buildit123    Ground Truth’? Can you explain what that is?


BT     Ground Truth’ is what I do.  I go out (on site to the property in question) and actually do the vegetation assessment on the actual block of land where you’re going to build. I do the vegetation assessment based on what I can actually see and using the information that I have. I can then compile my report and say  that either ‘yes’ there is a hazard here or in some cases I can come back to you and say ‘no’ there is no hazard here so there’s no requirement for you to address the Australian standard. (Note- that every site identified in the bushfire overlay needs to be assessed so you can understand exactly what it means for your project. This is a site by site exercise)


Buildit123    So just to clarify  – We’ve done the search, we’ve checked and the property in question falls within the Overlay.  But this doesn’t mean to say that they have to act on it. It really means that a physical site inspection & assessment needs to occur to determine what if anything needs to be addressed.


What is the purpose of the Bushfire Overlay? Why does it exist?

BT      The Australian standard AS 3959 2009 is there to provide a level of protection to people, which is obviously the most important thing and also a level of protection to the property. 

But the idea being, that in the event that someone is caught in their house in a bushfire, and they haven’t been able to get away, that that house will actually provide some protection for them until the fire front passes. 

That’s not to say that it won’t catch fire or that it won’t burn down but it’ll be more resistant to catching fire. And so they can provide that level of protection until the forefront passes. 


What sort of measures do people typically need to take if they are in a Bushfire Overlay?

BT    The Australian Standard sets out the level of assessment impact that might apply to any particular situation.  This is called a BAL rating – Bushfire Attack Level. 

This rating system starts at low, then 12 .5 then goes to 19 then 29,  40 and then goes to FZ. FZ stands for flame zone and that’s probably something we’ll touch on later but 12 .5 , 19, 29, 40,  those figures represent Heat flux impact. So 12 .5 represents 12 .5 kilowatts within a square meter of actual heat impact getting kicked out of here. 

So  up to a point there’s a requirement that your certified or your builder will then go to the Australian standard. Within the Australian standard it says. ‘For structures with 12.5 BAL rating, these are the things that need to be done.  Initially it’s generally about screens on windows and the actual glazing itself, nothing too onerous. . Yeah but obviously as the standard goes up to 18 and 29 and so forth, then the requirements start to increase. 

So the Bottom line is that these things cost money. [So the higher the BAL rating the more construction requirements under the AS which typically means a higher cost.]


ADDITIONAL INFO ABOUT BAL RATINGS ( not in the interview but talked about …)

The Australian Standard AS 3959 -2009 Construction of Buildings in Bushfire Prone Areas sets out the methodology to determine Bushfire Attack Level (BAL) that will impact a building.  BAL is a means of measuring the severity of a building’s potential exposure to ember attack, radiant heat and direct flame contact.


There are six  levels of BAL : LOW; 12.5; 19; 29; 40 & FZ (Flame zone).

The figures represent the heat flux exposure that a building would be subject to given as Kilowatts /m2 .


The main inputs into a BAL Assessment are :

  • Vegetation type and fuel Loads (Tonnes/Ha) It takes into account specific Queensland vegetation types
  • Horizontal distance to the classified vegetation
  • The slope of the land under the classified vegetation
  • The slope of the land between the classified vegetation and the site
  • Other factors – FFDI/ flame temp/ heat of combustion

The BAL classifications are:

LOW    No construction requirements

BAL 12.5    Ember attack

BAL 19    Increasing level of  embers and burning debris increasing heat flux

BAL 29    Increasing level of  embers and burning debris increasing heat flux

BAL 40    Increasing level of  embers and burning debris increasing heat flux with the likelihood of exposure to flame.

BAL FZ     Direct exposure to flames from a fire front + heat flux & ember attack



Photo Credit www.bushfireprone.com.au


The BAL level determines the specific construction standards for the building. 

The construction standards are designed to improve the ability of buildings in designated bushfire prone areas to better withstand  attack from bushfire and give a measure of protection to the building occupants (until the fire front passes ) and the building itself.

There is no guarantee that the application of the AS3959 -2009 will ensure a building surviving s bushfire event on every occasion.


Continuing on with our chat


When does the Bushfire Overlay apply?

Buildit123     We’re all about planning and One of the things that we were talking about  earlier was that people can get caught out when they’re well into the process with these types of things. 

So when does the Council essentially say ‘Hey wait a sec Bill, You’ve been zoned this and you need to invest some money in your house to be compliant against this overlay?


BT      Well in normal situation if you’re renovating or extending an existing house or even if you’re doing a new build on a residential lot,  once you have your development approval, the Council no longer has an input, 

It is your Building Certifier and that’s that’s who I prepare my reports for every day. I prepare my reports for a Certifier. The Certifier wants to see a report to says ‘this is what the BAL rating is’ and know that the report has been prepared and signed off on by a qualified professional. And we’ll usually include a Form 15 as well. [for the record, a Form 15 is a Compliance certificate for building design or specification)  In the case of where you’re doing a Material Change of Use or Reconfiguration of a lot, Known as a one into two  or a splitter then The Bushfire Hazard report needs to go in as part of your development application to Council. 


Buildit123     So then that comes part of your D.A.


BT     Yes  exactly.. So initially an individual build, or a small renovation,  those sorts of things will go to a Certifier who will determine what needs to occur. The Council doesn’t have any interest in that. Well not a direct interest. A Material Change of Use or Reconfiguration of a lot  it goes as part of the Development Application. 



The BAL assessment will determine the potential impact on the building. If there is a BAL impact, the AS 3959 – 2009 will be triggered and must be complied with. 

The construction standards are contained within the AS3959 -2009 –Construction of buildings in bushfire prone areas. Your building certifier will advise of the additional works required. 


Does this overlay typically apply only in the bush?  or does it also apply in the city?

BT      If you look at the Brisbane City Council mapping, you’ll find that places where there are fairly large retained areas of bushland like Seven Hills bushland reserve, in south Brisbane and those sorts of places where houses are surrounded by bush. That bushland actually has an expressed impact on houses. Those houses already exist there.  but in many cases now, the current trend is that people are renovating or extending these old houses. As part of that process, even though the house may have been built quite some time ago, any new work has to meet the Australian standard. 


Buildit123     So that’s a tip there really  – Just because you haven’t had to do it in the past, once you once you start doing some work on your house and probably trigger any town planning approval then these things will come up as part of the renovation works proposed.


BT      Or change. Yes. And as I just said , we were talking earlier about Material Change of Use or a Reconfiguration of a lot. Once you get to that level and type of development, it’s not only doing a BAL Assessment, Council will also require a Bushfire Hazard Assessment which is where you actually demonstrate that what you’re doing meets all the requirements in the City Plan. It cites things about access to water supply, emergency services, all those sorts of things. This is  a larger report generally not so much for one entity or reconfiguration but if you were suddenly going to develop maybe ten or twelve or 50 lots, this would be the requirement.

If you’re doing a bigger development,  your will want to make sure that you’re not placing people at risk. And when you do build there that there is access for better services. adequate water supply available,  emergency exits for the people who are in need. Things like that. But that’s more the commercial end.


Are fire ratings the same or similar Australiawide?

BT     Well it’s covered by an Australian Standard – AS 3959 -2009  Construction of buildings in bushfire prone areas and the Australian standard obviously says it applies right across Australia. 

The only difference is that the big impact in terms or the big potential impact is what sort of vegetation is involved.   We’ve recently seen examples and we’ve seen footage of the fires in South Australia, Victoria and southern New South Wales and we know that the vegetation there is much different and their fires have a lot more intensity than ours.  So the Australian standard takes into account the different types of vegetation that apply in different locations. We have the information from Queensland vegetation so that we can apply Queensland vegetation to our assessments.


What are the main things renovators should be aware of?              

BT      Well from my perspective there’s only one thing that people need to look at, and be aware of and that is ‘Am I in the  Bushfire Overlay or am I not’ and If I am under a bushfire overlay ‘What do I have to do’ Then they talk to their Certifier. who will either certify it or say you need to go away and find someone like myself who will prepare a Bushfire Attack Level report for you.

Once i’ve been briefed, then I work on that depending on what it is, I will then tell you what you have to do.


Buildit123 .    I think that’s the key here  –  Just because you’re in an overlay doesn’t mean to say you have to do something. knowing what you need to do to find out your responsibilities is key.


BT     It means you have to do something that may not necessarily mean that the impact will be onerous.


In Summary

Buildit123      So in summary all this needs to come into the planning of your whole renovation. So you’re not caught out at the end, This really what we’re trying to express here today – is that renovators are not caught at the end of it.  Being prepared is one of the main ways to avoid renovation disaster.

At Buildit123, as part of what we do,  we make sure that you know these things early, that you know to engage experts like Bernie when it’s required and just so as a renovator you don’t get caught short.


Buildit123     Bernie, we really appreciate your time out here today. It sounds like Bushfire can be a complex little beast and obviously that’s why you do what you do. For the average renovator, It’s about awareness and planning and. doing these things early, and ultimately about family safety and family protection.


BT     Yes s it’s there. It needs to be done. So you have to do it but it is it’s about protecting people and property issues.

Be aware any non compliant building work must be rectified before you can get you Building Approval.


Steps to take if you are in a Bushfire Overlay

Find out if you are the Overlay by either:

1.   Go to your Local authority planning scheme;  information and mapping will be available to  provide you with all the constraints that apply to a particular property i.e. Flood, landslip, fire, environmental etc.


2. Talk to a Building Certifier or a Town Planner or other professional like Buildit123.  It is their job to be aware of possible impacts or constraints that you may have to consider and budget for.

If you are the Overlay:

Engage a Bushfire Hazard Consultant to assess your proprerty and prepare a BAL Assessment report.

The BAL level will determines the specific construction standards required for fyour propsed building work.


Wrap Up

Our thanks to Bernie for taking the time to talk to us and share his knowledge and expertise.

If you have questions or need expert Bushfire advice contact Bernie directly at Queensland Bushfire Planning.


Remember, Knowledge is power and knowing and understanding easrly is one of the key factors of renovation success.

Research and knowing when you need expert help will save you time , money and minimise the chance of you being caught out.




While every effort has been made to provide accurate information, The Zen Reno does not guarantee that this blog article is free from errors or omissions or is suitable for your intended use. It is for information purposes only and expert advice should be sought regarding how this issue might affect your particular project.

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