Building for bushfire protection with Bluescope Steel
Bluesope Steel. Photo Credit: Lucas Dawson
Because of Australia’s inevitable urban sprawl, our desire to live close to nature, and our extreme weather conditions building designers continue to face rural environmental issues, not least that of bushfires.
Legislative provisions are in place to ensure appropriate bushfire protection measures are incorporated into the building and construction of new developments in bushfire prone areas; these vary according to the category of bushfire attack that a site falls into.
Well planned projects in these areas that make use of planning and development controls, construction standards (1), fire smart design - such as development position, layout, access and the use of non-combustible materials - and the provision of services, water supply and emergency management. They also include the creation of fuel reduced protection zones and suitable landscaping to help protect human life, property and environmental values from the impacts of bushfire events.
In Australia 80 per cent of homes destroyed by bushfire are built within 100m of bushland (2) however for most vegetation types, building more than 100m from the bushfire prone vegetation does not require any specific construction requirements. Regardless, building designers should provide basic measures of protection to minimise the chance of attack.
Most houses destroyed in bushfires survive the fire front but burn down during the following hours due to wind-borne burning debris.
Indeed, the two most common ways that houses are set alight are through embers or sparks that gain entry through gaps in wall cladding or roofing, and through radiant heat or direct flame which occur when something combustible is near the house - trees, scrubs, wood piles, for example.
During the design phase, consideration should be given to possible ember traps: where are the potential entry points; will there be enough trapped embers in vulnerable locations to cause ignition; and will ignition necessarily cause the loss of the building?
Commonly known methods of protection include window screens, gutter guards and the sealing of weepholes and external doors. In addition, the use of non-combustible materials can mean the difference between minor and major damage.
Colorbond steel products fare very well in conditions typically encountered during bushfires: embers, radiant heat and direct flame. Colorbond steel may be used wherever a non-combustible material is required, making it ideal for bushfire-prone areas.
The seamless nature of steel roofing and the way it’s fixed from the ridge to the eaves may help prevent the entry of spark and embers. Wall cladding made from Colorbond steel will provide a similar protective barrier.
Steel framing, made from Truecore steel, is also non-combustible so its use significantly reduces the amount of flammable material in a home. Additionally supported with non-combustible sisalations, insulations would add to the performance of Truecore steel in a fire.
Finally, the use of non-combustible barriers such as fencing, courtyards, fenced off areas for gardens, barbeque areas and the like, that can help to shield a home from the potential hazard, are strongly recommended.
In 2006, a CSIRO research study (3) found that solid steel fences provided a level of protection against bushfire attack that could be enough to prevent combustible items near the fence from igniting, thus reducing the chance of fire spreading into the inside of the property boundary.
For building designers a continued vigilance is needed when designing homes in high-threat areas where rural and urban land meets. However, the best planning can be undone by poor ongoing property maintenance and lack of forethought when landscaping a development. Thus future house protection ultimately depends on the homeowner.
Footnotes:
- The building requirements for each level of construction are set out in Australian Standard: 3959 (AS: 3959).
- NSW Rural Bushfire Service
- This project was managed by the Bushfire CRC and sponsored by BlueScope Steel. The Bushfire CRC is a national research centre developed in partnership with fire and land management agencies and research institutions, including the CSIRO, to reduce bushfire risk to the community. Results from this project add to growing efforts by the Bushfire CRC to help fire agencies and communities to better understand how to reduce bushfire risk.
22-May-2008