The extensive bushfires over the past six months have highlighted many of the issues involving environmental management, climate change, the adequacy of the fire fighting resources, and the construction standards of our houses.
Bushfire protection measures for residential construction were first introduced in New South Wales in 1999. These measures were extensively revised in 2009 with the introduction of Australian Standard AS 3959.
There are many misconceptions and fears regarding the increased cost of these bushfire measures. In this blog, we give a preliminary outline of the bushfire controls and the implications for the typical homeowner.
Compliance with the local government before purchasing or building
Each Council has maps showing the bushfire prone land within their local government boundaries. While the extent of designated bushfire prone land is surprisingly far-reaching, in most cases, the measures required are not onerous and are relatively easy to incorporate.
Every individual site within a bushfire prone area must be assessed for the level of bushfire protection required. The assessment includes an examination of the ground slope or gradient, the type and density of vegetation and the distance of the property from large areas of bushland.
From the assessment of the site and its surroundings, calculations are completed to determine the fire fuel load and the severity of a potential fire. From these calculations, the rating of the site is classified under a Bushfire Attack Level, or “BAL” rating.
The BAL ratings from the lowest (least dangerous) to the highest (most dangerous) are as follows: BAL 12.5, BAL 19, BAL 29, BAL 40 and lastly Flame Zone (FZ).
Determining your BAL rating
The State Government has an online rating form to enable a Home Owner to complete their own site assessment. We suggest that this Do-It-Yourself method only be attempted by people with some relevant technical knowledge.
There are serious consequences for property loss, family safety and insurance coverage if this assessment is found to be incorrect after a fire event – so we recommend an experienced and qualified bushfire consultant be employed to assess the BAL rating and other bushfire measures.
A consultant can give a more accurate assessment, recommend a range of alternative solutions, and liaise with Council and the Rural Fire Service if necessary. A consultant can also sometimes save money on the construction cost of fire protection measures through alternative solutions.
The cost of these reports varies from site to site commencing from $600 and increasing for remote and complicated assessments.
Potential bushfire protection measures
Depending on the BAL rating, the bushfire protection measures can range from:
- Upgrade insect screens from fibreglass to metal mesh.
- Inclusion of metal leaf guards to roof gutters.
- Enclosure of open underfloor areas.
- Certain hardwood timbers for external use.
- Tiled decks or verandahs in lieu of timber.
- Toughened glass in lieu of normal float glass.
- Restrictions on the type of cladding.
- Metal fencing in lieu of timber fences.
- Restrictions on landscaping adjacent the house.
- Provision of a cleared area Asset Protection Zone (APZ) surrounding the site or house.
- Fire shutters to windows and doors.
- Provision of designated water storage for fire fighting.
For many building products (windows, cladding, roofing, decking, etc) the manufacturers now include the approved BAL rating for their products. Sometimes for roof and wall construction, a composite system i.e. a combination of framing,
sarking, insulation, and cladding has been tested as a complete system to achieve a certain BAL rating.
Bushfire controls & new additions
Home Owners undertaking additions must be aware that the bushfire controls also apply to new work. While it may not seem logical, the existing house can remain as originally built, however, any new work must be compliant.
The regulators assume the new work, built to a higher standard, may offer refuge during a bushfire (this would appear to be an extremely optimistic hope rather than a realistic outcome).
Generally, the lower BAL ratings (12.5, 19 and 29) are not too onerous with the bushfire provisions best incorporated during the design stage.
The higher BAL ratings (40 and Flame Zone) present a bigger challenge with the provisions requiring construction systems and materials to be selected from a limited range of suitable products.
The Flame Zone provisions have been written primarily for remote properties where attendance by firefighters may not be possible. However, a Flame Zone rating can also be triggered in a suburban setting e.g. a house bordering a large nature reserve. It is the Flame Zone provisions that are difficult and expensive to incorporate.
When evaluating a number of possible house sites before purchasing a property, the buyer should consider the potential bushfire implications. Any lots close to large areas of bushland should be checked for the BAL rating prior to purchase.
Where possible any sites assessed as Flame Zone should be avoided.
Bushfire prevention and controls are not as expensive (or complicated) as you might think
In summary, the bushfire provisions do not impose a large addition to the cost of construction in the majority of situations.
Sites in remote locations or adjacent large areas of bush are those most likely to incur higher costs to meet the requirements. As Architects, we are familiar with the range of bushfire protection measures. We work closely with a Bushfire Consultant to minimise the cost impacts while still achieving attractive houses compliant with the controls.
We can help you with the preliminary assessment of the potential bushfire impact and what this may mean for your proposed development.