By all accounts, Australia’s bushfire crisis has been devastating.
For now, priorities centre around supporting those affected.
Longer term, however, we need to think about how development controls and design/construction methods and materials should change in response to greater levels of fire hazard.
The importance of such issues was drawn out during Victoria’s Royal Commission into the Black Saturday Bushfires. Of 67 recommendations in that Commission’s final report, nineteen related to planning/development and construction.
This raises questions about how Australia is performing regarding bushfire protection in planning and building as well as how we can improve moving forward.
For answers, Sourceable spoke with two speakers from the Australian Bushfire Building Conference held in the Blue Mountains last October. These are Dr Grahame Douglas, Academic Course Advisor for Bushfire in the School of Built Environment at Western Sydney University who previously worked with the Rural Fire Services in community safety for fifteen years and Wendy Bergsma, director of building design practice Dream Design Build in the NSW town of Tathra.
As things stand, the main performance requirement in the National Construction Code (NCC) which deals with bushfire risk is Performance Requirement P2.3.4 of Volume Two in NCC 2019 (GP20 applies in relation to Volume 1). This applies to all Class 1 and Class 10a buildings (single-storey homes as well as private garages, carports and sheds) which are built within areas that are designated to be bushfire prone. It requires such homes to be designed and constructed to reduce the risk of bushfire as appropriate according to both (a) the potential for ignition to be caused by burning embers, radiant heat or flame as well as (b) the likely intensity of any bushfire attack.
To meet these requirements, buildings must either comply with Australian Standard AS 3959 (Construction of buildings in bushfire prone area) or use a performance solution which meets the requirements. To meet AS 3959, buildings must satisfy certain requirements which vary according to the Bushfire Attack Level (BAL) rating that the property in question is assigned. These requirements cover material specification, elements of construction and construction systems. They relate to areas such as floors, roofs, walls, windows, verandas and carports.\
Asked about current building and planning performance, Douglas says anecdotal evidence suggests that current controls are helping. In the 2013 Blue Mountains fires, for example, the proportion of homes which were constructed under the current standard for bushfire protection and were lost was smaller than that which would have been expected to be lost in the past.
Nevertheless, he says deficiencies exist in two areas.
First, there are concerns about the weather conditions which are used for design requirements in Queensland and parts of New South Wales.
In the south coast of NSW, the required conditions for fire design are such that homes need to be constructed to a standard which would be expected to survive a bushfire on a day where the Macarthur Forest Fire Danger Index (FDI) developed by CSIRO scientist A.G. Macarthur reaches anything up to 100. In Northern and Central NSW and Queensland, however, Douglas says the FDI upon which fire design conditions are based is set at 80 and just 40 respectively.
This, Douglas says, is inadequate. Based on a fire event which is expected to occur approximately once in every fifty years, he says Queensland should be at an FDI level of 100 whilst the north coast of NSW should also be at 100.
Second, Douglas points to concerns about some non-residential buildings. As mentioned above, specific NCC provisions apply for single storey residential dwellings in bushfire prone areas and in Class 2 and 3 buildings. However, no such protection is afforded to other buildings such as Class 9 buildings (such as aged care, or healthcare and public buildings) even where these lie in bushfire prone areas.
A particular concern involves buildings such as hospitals, schools, aged care facilities and childcare facilities which house occupants who are likely to be vulnerable in a fire. As part of its final report, the Victorian Bushfire Commission referred to above recommended that specific bushfire construction provisions in respect of such buildings be inserted into what was then the Buidling Code of Australia (now the NCC). The Commission also recommended that the NCC apply a minimum AS 3959-2009 construction level of BAL-12.5 (low risk) to all new buildings and extensions in bushfire-prone areas.
This, however, has not been done.
To be sure, some states have inserted added protection in their own building regulations. In NSW, a State variation applies which captures Class 4 and 9 buildings. In Victoria these are captured under the Building regulations. Tasmania also addresses issues largely through planning.
Elsewhere, however, there is no protection for non-residential buildings outside of Class 2 and Class 3 buildings. As such, non-residential buildings outside of these states (apart from Class 2 and 3 buildings) are not subject to any specific bushfire related requirements even when they are in bushfire prone areas.
Bergsma agrees that challenges exist.
Speaking about building and planning controls, she cautions that incidences of homes being destroyed in current and past fires may not be reflective of current development and building controls as many of these homes would have been constructed under controls which preceded those in place today.
As well, she says many homes which have been lost in current/recent bushfires have not been rural properties in the bush but rather urban properties in regional and local towns. In many cases, these have in fact been outside areas which have been deemed to be bushfire prone.
On that point, Bergsma says consideration must be given to the factors which can physically cause houses to burn down. Some homes, for example, could be at risk where they sit underneath overhanging trees. Items such as rubbish, leaves, litter and debris could serve as a sources of fuel. Given the proximity of homes to each other in township areas, fires which affect one home can also spread to neighbouring properties.
Speaking particularly of construction methods and regulation, Bergsma says the current BAL ratings focus too narrowly on construction elements such as material selection and give insufficient consideration to design considerations such the design of roofs and the interface of properties with the bush. As well, she says BAL ratings place too greater weight on the distance which the fire must travel from the bush to reach the dwelling as opposed to the risk of homes being impacted through ember attack.
Going forward, Bergsma would like action in several areas.
From a development control viewpoint, she would like a more extensive application of asset protection zones in country towns and some suburban areas. These are areas under which surround critical assets or homes in which efforts to minimise fuel loads with regard to fires are undertaken.
Next, careful study should be undertaken in respect of buildings constructed after the Black Saturday bushfires to determine the extent to which lessons learned through the Royal Commission into that fire are being applied in new dwellings.
Greater study is also needed into the specifics about what has caused homes to burn down in current and past fires. This would include identifying the proportion which are lost because of ember attack as opposed to direct bushfire contact with the side of the dwelling.
From this could spring two further initiatives.
First, better information and education could be provided to residents about how to prepare their homes and themselves in the event that a fire does occur. This could include information on reducing fuel loads such as leaf litter and debris.
Second, there could be consideration to changes in planning and vegetation. Issues such as having large numbers of gum trees in urban areas could be considered.
Douglas, meanwhile, would like action in several areas.
First, he talks of a need to expand the types of buildings which are protected by specific bushfire-related measures in design and construction. In particular, he says protection measures should be applied nationally to hospitals, schools and other buildings which accommodate vulnerable populations. Whilst as mentioned above, NSW, Victoria and Tasmania have acted on this, he says other states need to catch up. In addition, he says parts of Class 4 buildings which are residential in nature should be protected.
Next, specific measures are needed to reduce fuel loads in and immediately around buildings and homes, and not on necessarily on adjoining natural areas. Since many desire to live with trees that either overhang or are within immediate proximity of their homes, features such as gutter or valley guards for buildings should be mandatory in areas with trees. So too should the use of non-combustible sarking materials in walls in roofs: currently, Douglas says AS 3959 allows for sarking materials with a flammability index of less than five to be used. In addition, particularly in homes which are rated within the lower BAL levels, more must be done to prevent embers from entering subfloor systems which are elevated off the ground. Currently, Douglas says AS3959 allows the floor height to be more than 400 millimetres above the ground without specific protection. This, he says, not only enables embers to potentially enter the subfloor system but also encourages use of subfloor space for storage. Potentially, this could serve as fuel in a fire. Requirements are needed in the proper placement of LPG used in rural and village areas so that gas bottles do not become a source of fire and threaten fire fighters or homes, he adds.
Next, Douglas says is important to learn from past and current fires about how to improve the design of subdivisions through appropriate road networks and separation between urban form and rural bushland areas.
Fourth, he says we need to move beyond compliance and apply innovate design strategies to reduce the risk which bushfires present to buildings. Asked specifically about this, Douglas stresses that appropriate measures will vary according to individual cases. Nevertheless, he says there have been cases where solutions have been devised that integrate the urban form in a way which both a maximises safety and retains beauty and attractiveness. (However, when selling properties, Douglas says vendors should be required to ensure the property is compliant with the planning and building provisions imposed including the maintenance of asset protection zones as well as construction standards.)
Finally, greater effort is needed to educate designers and planners about bushfire protection.
Douglas says this is critical.
“We need to do a better job of educating our architects, our planners and our building designers about what we need to do in respect of natural disasters,” Douglas said.
“Planning universities do not adequately deal with natural disasters – especially bushfire but also more generally. They need to step up. Architecture schools do not adequately deal with issues of building in bushfire prone areas or building regulations.
“We need to get universities, architecture schools and planning courses to integrate bushfire protection as part of the standard treatment of educational understandings of those professions.”