What is a BAL assessment?

A BAL assessment is usually undertaken after a bushfire hazard level assessment has been conducted and provides a detailed assessment of risk. Land capability and suitability for development should already be determined by the time a BAL assessment is prepared.

A BAL assessment classifies land into six categories based on a combination of vegetation type (fuel type, load and structure), effective slope of the land, and the proposed building’s distance from predominant vegetation. The BAL descriptions and assessment methodology are located in AS3959, referenced in the BCA, and reprinted below:


BAL
    Description
       
BAL-
LOW
    There is insufficient risk to warrant any specific construction requirements but there is still some risk. Residents should still do basic property preparation.
       
BAL-
12.5
    Although the risk is considered to be Low, there is a risk of an ember attack. Attack by burning debris is significant with low levels of radiant heat (not greater than 12.5kW/m2). Radiant heat is unlikley to threaten building elements (i.e. unscreened glass). Specific construction requirements for ember protection and accumulation of debris are warranted (Level 1 construction standards). 
       
BAL-
19
    There is a risk of ember attack and burning debris ignited by wind-bourne embers and a likelihood of exposure to radiant heat. Attack by burnning debris is significant with an increased radiant heat levels (not greater than 19kW/m2) threatening some building elements. Specific construction requirements for protection against embers and radiant heat are warranted (Level 2 construction standards).
       
BAL-
29
    There is an increased risk of ember attack and burning debris ignited by wind-borne embers and a likelihood of exposure to an increased level of radiant heat. Attack by burning debris is significant and radiant heat levels (not greater than 29kW/m2) can threated building integrity. There are specific construction requirements for protection against embers and higher radiant heat are warranted. There is some flame contact which is possible.
       

BAL-
40

    There is much increased risk of ember attack and burning debris ignited by wind-borne embers, a likelihood of exposure to a high level of radiant heat and some likelihood of direct exposure to flames from the fire front. Increased attack from burning debris wih significant radiant heat and the potential for flame contact. The extreme radiant heat and potential glame contact could threaten building integrity. Buildings must be designed and constructed in a manner that can with stand the extreme heat and potential flame contact. 

Not supported by planning.
       

BAL-
Flame Zone

    There is an extremely high risk of ember attack and burning debris ignited by wind-bourne embers, and a likelihood of exposure to an extreme level of radiant heat and direct exposure to flames from the fire front. Radiant heat levels will exceed 40 kW/m2.

Radiant heat levels and flame contact are likely to significantly threaten building integrity and result in significant risk to residents who are unlikely to be adequately protected. The flame zone is outside the scope of the BCA and the NSW Rural Fire Service may recommend protection measures where the applicant does not provide an adequate performance solution. Other measures such as drenching systems and radian theat barriers may also be required.

Any permanent modification to vegetation type or structure or a development’s distance from vegetation may modify the BAL and therefore the required construction standard. The construction requirements are only formally applied to buildings and incidental structures in bushfire-prone areas at the building permit stage.

A BAL assessment is required for any development application on a site classified as having a moderate or extreme bushfire hazard level.


What is AS 3959?

AS 3959 is the adopted Australian Standard (3959) for the Construction of Buildings in Bushfire-Prone Areas. It specifies the construction requirements for each BAL Level.

My Property is shown as being in a Bushfire Prone Area. What does this mean?

If you want to build a new house, extend your existing house, or build a shed you will need to have an assessment done, by a qualified and experienced person, to determine the BAL that affects your property.

My property is shown as being in a Bushfire Prone Area, but I already have a house on it. Do I need to do anything?

No, you don’t need to do anything to your existing property. If you are in the process of extend and renovating your existing house, or build a shed or garage etc. you will need to comply with the requirements.

What is a Bushfire Prone Area?

It is an area identified as being subject to a bushfire risk. It includes all land that is subject to a bushfire hazard and a buffer of 100 m around the hazard. The scheme Amendment includes maps which show all Bushfire Prone Areas.

Who decides which areas are bushfire prone?

Currently the designation of bushfire prone areas is the responsibility of each local authority. Each local authorities planning department will be able to advise you if your property has been designated as bushfire prone. In the future, state-wide designation of bushfire prone areas is planned to be introduced.

Are there any measures I can take to reduce bushfire risk within my property?

The best measure to take to reduce bushfire risk within your property is to make sure you are complying with any fire management plans, fire break notices, or any other requirements applicable to you. Contact your local authority and ask if there are any fire management requirements in place.  DFES also provides standards to assist in creating areas of safely maintained vegetation around your building, see DFES Building Protection Zones. Note that approval to remove vegetation should be sought from your local authority where appropriate.

I have previously built without needing to comply with BAL requirements, why is this a requirement for building now?

AS 3959 (Construction of Building in Bushfire Prone Areas) was revised in March of 2009, and was brought into effect with the 2010 edition of the BCA. Local authorities have been working to identify and designate areas that are bushfire prone after this change, with different areas being designated at different times.

Can I do my own Bushfire Assessment?

Yes, however, if you get it wrong it could prove costly. Employing a bushfire consultant is recommended. Section 2 or AS 3959 deals with assessing Bushfire Attack Levels. There are two methods - a simplified method, and a detailed method.

Has AS 3959-2009 undergone any sort of cost benefit analysis to demonstrate that there would be savings versus the costs involved?

Yes, the Australian Building Codes Board (ABCB), the developer of the Building Code of Australia (BCA), conducted a comprehensive Reulatory Impact Statement (RIS) in December 2008 and their findings show that the 2009 edition of AS 3959 provides cost benefits when compared to the 1999 edition.

My proposed new home site is on a steep slope and I am concerned it would be a bushfire risk. What do I do?

The type of vegetation on the slope is very important. Australian Standard® AS 3959- 2009 limits the slope to 20 degrees; Slopes greater 20 degrees would need a special assessment. WA BAL will be able to specially assess your site to determine how much bearing the slope will have.