Do I need to build my house to a higher standard than a normal house?
If your building site is in a ‘bushfire Prone Area’, and is rated at BAL-12.5 or higher, your house is required to be constructed to a higher bushfire resisting standard than a non-rated house. (Refer to the separate headings below for further information on ‘Bushfire Prone Areas’ and ‘BAL ratings’).
The level of additional upgraded materials and/or prevention measures will increase as the BAL rating increases. This in turn will increase the cost of the building.
Affected areas are limited to the exterior of the building. In general these include the upgrading of exposed timbers to more fire resistant species, to fibre cement or steel; the strengthening of exterior glazing and flyscreening, and in some cases the inclusion of shutters; the sealing of all exterior gaps for the prevention of ember entry; and the upgrading of wall cladding materials and soffit linings to more heat resistant materials.
What can Paal do to help?
Paal Kit Homes can help guide you through this process. In most cases we can assist you with an initial understanding of your bushfire attack level (BAL rating), and can provide you with an indication of the costs and obligations.
Paal Kit Homes has an extensive understanding of the house construction requirements necessary to meet your BAL rating. This includes BAL ratings up to the highest level of BAL-FZ (Flame Zone). Paal will ensure that the materials supplied will meet or exceed the level required.
Typical material upgrading can include -
- Steel verandah posts and verandah post beams
- All external timber trimming supplied in fire resistant timber or fibre cement
- All external entry doors and door frames are ungraded
- Improved verandah and Alfresco linings
- Improved window construction, including thickened toughened glass
- Sealing of all roof ridges, hips and valleys to prevent entry of embers
Note that the amount of upgrading required will depend on your actual BAL rating, Paal can advise on your exact requirements once the BAL rating is known.
What is a BAL rating?
BAL stands for ‘Bushfire Attack Level’. The number following the BAL prefix indicates a measurement of the ‘radiant heat’ the constructed building is required to withstand. For example, a figure of BAL-12.5 indicates a residence needs to be constructed in a way that it can withstand radiant heat up to a level of 12.5 kilowatts per square.
There are various standard BAL categories – BAL-Low, BAL-12.5, BAL-19, BAL-29, BAL-40 and BAL-FZ. When you are constructing in a ‘Bushfire Prone Area’ your Council or Certifier will require your house to meet the construction standards of one of these categories.
In all cases the actual flame contact from a fire is not taken into consideration until the highest level of BAL-FZ is encountered. However, the closer the building is to the fire source the higher the radiant heat levels will be.
The various levels of bushfire resisting construction exist because radiant heat has the ability to weaken and/or set fire to building materials at varying levels of radiant heat. This may result in embers gaining entry to the building which could then set the building alight. This can occur even though the flame from the bushfire has not actually come into contact with the building.
How is a BAL rating determined?
The BAL rating is determined by a number of factors. These include –
- Your proximity to the bushfire threat, i.e. the closer you are, the higher the radiant heat level will be in the event of a bushfire.
- The type of vegetation that poses the threat. For example, higher heat levels can be expected from dense eucalypt forest than from open woodlands or rainforest.
- The slope on which the vegetation exists. Fire races up a hill with more intensity, speed and flame length than fire coming down a hill. If your building site is located at the top of a vegetated slope you will be required to build to a higher BAL rating than someone building at the bottom of a vegetated slope.
All of these factors are measured and placed into a table that is in Australian Standard AS3959 – ‘Construction of Buildings in Bushfire Prone Areas’. This is the National reference document for specifying construction materials required in Bushfire Prone Areas. The table determines your individual BAL rating based on the above factors.
The State of Victoria produces a handy guide to understanding this process. A copy of the guide may be found here.
What is a Bushfire Prone area?
A Bushfire Prone area occurs where residential building sites are located within close proximity to a potential bushfire hazard. A bushfire hazard is generally identified as an area of unmanaged native Australian bushland.
The various State Government Authorities throughout Australia produce mapping services which identify the bushland areas which are likely to impose such a threat. The mapping services indicate areas of native vegetation and a ‘buffer zone’ (usually 100m wide). If either the native vegetation or the buffer zone crosses over your building allotment, your property will be deemed ‘Bushfire Prone’.
If your property is ‘Bushfire Prone’ you are required to construct your residence to a higher level of bushfire resistance then would otherwise be the case. You will also be required to submit a bushfire assessment report with your building application.
Note - the mapping services only identify areas of bushland threat, however open grassland areas may also pose a threat. For this reason many rural properties will be required to meet a minimum standard regardless of the mapping indication.
It is also worth noting that the State of Victoria applies a minimum standard of BAL-12.5 on all properties regardless of your proximity to a bushfire threat.
How do I find out what my BAL rating is?
First step is to check if your site is bushfire prone. You can do this on-line, or through your local council or bushfire authority. If you type into an internet search engine “is my property in a bushfire prone area NSW” (substitute your own State accordingly), you will quickly be directed to the mapping service for your State.
If your site is designated as ‘Bushfire Prone’ you may determine your BAL rating by one of the following methods. Note that the requirements vary from State to State so not all methods may be possible in all States.
- You may do it yourself (not recommended unless you have previous experience or are well researched).
- The local bushfire authority may assist you with the calculations, or in some areas may actually determine it.
- Your Council or Certifier may assist you with the calculations, or in some areas may determine it.
- By employing the services of a Bushfire Consultant or an experienced building practitioner to assess the site and prepare a report.
Note that in some cases the Bushfire Buffer Zone may cross your property, and therefore deem your land ‘Bushfire Prone’. However if your actual building site is located outside of the Bushfire Buffer Zone or areas mapped as native vegetation, you may be designated ‘BAL-Low’. If so, you do not need to provide any specific bushfire building requirements. Although you may like to consider some precautionary measures, particularly to prevent the entry of embers.
Other precautionary measures
In addition to preparing your new residence for possible Bushfire attack, you will also need to budget for some additional measures.
It is often necessary to retain water on site for firefighting purposes. This is usually stored in a rainwater tank with a dedicated capacity for the purpose. You will need to allow this in addition to any water supply you otherwise intend to hold on site. Often it is also necessary to have a petrol/diesel firefighting pump.
Attention may also be required with the landscaping on your site, in particular if your site is a larger allotment. This may include management and/or clearing of native vegetation to establish an Asset Protection Zone (APZ) around your house. Clearing may also extend to the widening of access driveways and turning bays for firefighting vehicles.