Building in Bushfire Prone Areas, Considerations for Construction
Australians have a fundamental connection to the bush. Much of our cultural folklore surrounds Australia’s beautiful bushland areas. It is of little surprise then that many of us share a desire to build our dream home in such an area. In addition, the increasing urban sprawl of most major Australian cities is leading to increased residential construction in areas that have a high chance of bushfire.
The frequency and severity of bushfires in Australia as result of climate change is increasing, this was clearly evident by the tragic events of Black Saturday on 7 February 2009 in Victoria as well as many significant bushfire events since including the Blue Mountains fires in 2013. These events have led to a number of revisions in building codes and standards in relation to bushfire construction in Australia, in order to reduce the potential impact of these events in the future.
All of this leads to significant need for rigorous and safe bushfire construction measures to be implemented in a consistent and nationally harmonised way, and then be applied in a uniform manner by designers, certifiers and builders. This article will detail some important considerations when designing and constructing residential houses in bushfire prone areas for builders and property owners.
Understanding the legislative framework for bushfire construction in Australia
The construction of buildings in bushfire prone areas throughout Australia is generally governed by both the land use planning and building regulatory frameworks. In New South Wales , as an example, development for residential purposes on bushfire prone land must comply with the Environmental Planning and Assessment Act including Planning for Bushfire Protection published by the NSW Rural Fire Service or where applicable State Environmental Planning Policy (Exempt and Complying Development Codes) 2008. Each state and territory will have its own requirements in this regard.
As readers of this publication would no doubt understand, construction in Australia is prescribed by the National Construction Code. Notwithstanding any land use planning requirements, standalone residential housing construction in bushfire prone areas is specifically controlled by part 3.7.4 within volume 2 of the Building Code of Australia “class 1 and class 10 buildings.” This part generally calls up some or all aspects of Australian Standard AS 3959-2009 Construction of Buildings in Bushfire Prone Areas as the primary reference document for construction requirements.
In New South Wales AS 3959-2009 is called up as the Deemed to Satisfy solution with the exception of Section 9 for Flame Zone construction. Buildings that are assessed as requiring Flame Zone construction are required to comply with Planning for Bushfire Protection including any specific measures required by the Rural Fire Service through a Bushfire Safety Authority which forms part of the Development Approval for the land.
While the standard is generally applied across all states and territories in Australia, the way it is implemented may vary based on the requirements of various pieces of relevant legislation. These state based regulations primarily vary the planning requirements / instruments required for applying the standard and may tweak elements of the Standard, however, as a general rule the overall the requirements of AS 3959 are fundamentally the same across Australian jurisdictions.
An important component of construction in bushfire prone areas is determining the Bushfire Attack Level (BAL). The BAL is determined via combining the values of a range of measurements including the Fire Danger Rating for a given area, the vegetation classification, distance of proposed building site from vegetation and effective slope of the land proposed for development. There are five Bushfire Attack Levels as follows: BAL-12.5, BAL-19, BAL-29, BAL 40 and BAL-FZ. The numbers associated with each BAL level denote anticipated levels of radiant heat by kilowatts, while BAL-FZ stands for Flame Zone, the highest bushfire attack rating.
Bushfire rated construction materials
AS 3959-2009 is primarily concerned with improving the ability of buildings to better withstand attack from bushfire thus giving a measure of protection to the building occupants (until the fire front passes) as well as to the building itself.
Of significance to AS 3959-2009 was the publication (in 2007) of the AS 1530.8 series of standards that set out methods of test for building materials, elements of construction and systems subjected to bushfire conditions.
The publication of these standards provides confidence to builders and consumers that the use of products that have been demonstrated to meet specific test requirements will result in a safer building. The Standards also provide manufacturers with a standardised process and allows for fair and consistent evaluation of products.
AS 3959 -2009 allows for the use of tested materials, but it also allows for the use of other materials and components that have been deemed, but not tested, to withstand the assessed level of bushfire impact. FPA Australia believes that all products used in bushfire prone construction should be based on the results of testing.
Benefits of using tested construction materials
The main benefit of using a tested system or component is that only the specific materials and construction techniques used in the tested system can be deployed. This ensures that the final product when installed in the building will perform in the same manner as that originally evaluated by the Registered Testing Authority.
In contrast to a fully tested and certified system, use of a generic system or a non-tested product such as that detailed in Appendix I of AS 3959-2009 for roof systems does not allow for any control over the type of materials used or the method of installation.
FPA Australia considers that this makes a generic system or non-tested product far less reliable than a tested or certified system. This concern stems from the fact that there is no guarantee that the types of materials ultimately used on site will match those that were used in the testing and evaluation undertaken by the Registered Testing Authority.
FPA Australia considers that a generic system that uses different materials, or applies different construction techniques to those used in the testing and evaluation of an approved system may not pass the required test and therefore the building may be more venerable to the effects of a bushfire.
The selection of plywood installed as part of a generic system is an example of where different materials could be used. Plywood is a manufactured wood panel made from thin sheets of wood veneer. In Australia, plywood is widely available in many varying forms from numerous product manufacturers and importers. Plywood can be manufactured from softwood, hardwood and tropical timbers and the thin sheets of wood veneer can be bonded together using a variety of different glue products. Such variations in plywood production make it most unlikely that all brands of plywood will perform the same when tested under fire conditions. This is just one example of where product selection could influence the performance of a generic system.
New Technologies and Products
FPA Australia acknowledges that the initial application of AS 3959–2009 throughout Australia was troublesome for property owners, particularly those assessed as being subjected to a BAL-FZ rating. This was in part due to the unexpected adoption of AS 3959–2009 shortly after the Black Saturday fires. The rapid publication of the standard which included referencing of the newly developed AS 1530.8 standards, unfortunately meant that there was little opportunity for products to be developed and tested to comply with the new test standard.
Despite the problems associated with the initial publication of the standard, industry has responded by investing considerable funds to design and test systems to meet the new requirements. In fact the rapid release of the standard not only encouraged innovation, but defined an expected level of performance and an even playing field. This has resulted in an increased, yet appropriate level of protection for the community.
Referencing the AS 1530.8 series of standards as a benchmark requirement has created a demand for tested product that industry has responded to and continues to innovate towards. Multiple products that have been tested to and found to comply with the test standards are now available in the marketplace.
Home owners have a right to expect that design and construction to a particular assessed BAL level means just that. Any opportunity for a reduction in performance, inadvertently or otherwise through the use of generic systems or untested products should be very carefully considered to ensure consumer and community safety is respected as the priority when determining construction in bushfire prone areas.
Using Accredited Practitioners
All of the points outlined above highlight the importance of property owners and developers using trained, professional practitioners when bushfire reports are required during the planning, approval and development process when building in bushfire prone areas.
In order to meet this need Fire Protection Association Australia has developed the Bushfire Planning & Design Accreditation Scheme (BPAD). The Scheme accredits consultants who offer bushfire assessment, planning, design and advice services. BPAD practitioners meet criteria based on specific accreditation and competency requirements, including a detailed knowledge of the relevant planning, development and building legislation for each State and Territory. Through the Accreditation Scheme, BPAD Accredited Practitioners are recognised by industry, regulators, fire agencies, end-users and the community as providers of professional bushfire assessment, planning, design and advice services. The Scheme provides an enhanced level of confidence for government and the community that practitioners are accredited by a suitably robust scheme that is administered by the peak national body for fire safety.
Accredited practitioners are able to provide advice pre-construction and post-construction with respect to product selection, testing and compliance with AS 3959 -2009 and any required development approval. In addition an accredited practitioner can provide advice in relation to additional bushfire safety measures that are not prescribed as the minimum requirements. These measures can include the application of bushfire sprayer systems, construction and use of private bushfire shelters, emergency planning and bushfire survival plans and appropriate landscaping to reduce bushfire impact.
For more information about finding bushfire-tested building products visit www.fpaa.com.au/providers. for information about the BPAD scheme visit ww.fpaa.com.au/bpad or call the FPA Australia National Office on 03 8892 3131.
For more information, go to www.fpaa.com.au/bpad