As Australians face the effects of the devastating bushfire crisis, the first priority must be to support those whose lives and homes have been horribly devastated. The second priority is to alter and reform development controls and design/construction methods and adopt the use of new materials to respond to intensified levels of fire hazard.
The importance of these issues was addressed during Victoria’s Royal Commission into the Black Saturday Bushfires. From the 67 stated recommendations in the Commission’s concluding report, nineteen pertained to planning, development and building.
This prompts us to consider as to how Australia is performing in regards to bushfire protection in planning and building, along with ways in which we can improve in the future.
Two speakers offered prime advice on this subject at the Australian Bushfire Building Conference, which took place in October at the Blue Mountains. They are Dr. Grahame Douglas, Academic Course Advisor for Bushfire in the School of Built Environment at Western Sydney University and previous employee of Rural Fire Services, having worked in their community safety department for fifteen years; and Wendy Bergsma, director of building design practice for Dream Design Build in the NSW town of Tathra.
The primary performance requirement stated in the National Construction Code (NCC) in regards to bushfire risk is Performance Requirement P2.3.4 of Volume Two in NCC 2019 (GP20 applies in relation to Volume 1). This pertains to Class 1 and Class 10a buildings (single-storey homes, private garages, carports and sheds) constructed in areas designated as bushfire prone. It mandates that these homes be designed and built to alleviate the risk of bushfire in accordance with both (a) the potential for fire ignition to be prompted by burning embers, radiant heat or flame and (b) the probable intensity of a bushfire attack.
To adhere to these mandates, buildings must stand in compliance with Australian Standard AS 3959 (Construction of buildings in bushfire prone area) or apply a performance solution that adheres to these requirements. To meet AS 3959, buildings must meet requirements that vary in accordance with the Bushfire Attack Level (BAL) rating that the property is given. These guidelines concern material specification, construction elements and building systems. They pertain to home areas like floors, roofs, walls, windows, verandas and carports.
When queried in regards to today’s building and planning performance, Douglas asserts that current controls are doing their job. In the 2013 Blue Mountains fires, the percentage of homes built under the contemporary standard for bushfire protection that were destroyed was smaller than what would have been lost in the past.
He also, however, sees room for improvement.
He sees a problem in the weather condition guidelines used for design requirements in Queensland and regions of New South Wales.
On the NSW south coast, the required conditions for fire design mandate that houses must be constructed in accordance with a standard expected to withstand a bushfire on a day on which the Macarthur Forest Fire Danger Index (FDI), developed by CSIRO scientist A.G. Macarthur, reached any level up to 100. Yet in Northern and Central NSW and Queensland, Douglas states that the FDI on which fire design conditions are based is established at 80 and 40 respectively.
This, in his view, is insufficient. Based upon a fire event expected to happen about once every fifty years, he asserts that Queensland should stand at a FDI level of 100, while the north coast of NSW also should stand at 100.
Secondly, Douglas references concerns regarding non-residential buildings. True, specified NCC provisions apply to single storey homes in bushfire prone areas and in Class 2 and 3 buildings. Yet no protection is offered other structures like Class 9 buildings (like senior aged care, or healthcare and public buildings) even when those are located in bushfire prone vicinities.
A specific worry revolves around buildings like hospitals, schools, senior care and childcare facilities which shelter occupants who would be vulnerable in a fire. As a component of its final report, the Victorian Bushfire Commission referenced the recommendations that specific bushfire construction provisions in regards to such buildings be added to what previously was the Buidling Code of Australia, presently the NCC. The Commission in addition recommended that the NCC apply a minimum AS 3959-2009 construction level of BAL-12.5 (low risk) to new structures and extensions in bushfire-prone areas.
Yet this was not completed.
Certain states have fortified their own building rules with enhanced protection. In NSW, a State variation is in effect which includes Class 4 and 9 buildings. In Victoria these are outlined in Building regulations. Tasmania deals with these issues through planning mechanisms.
In other regions, however, no protection exists for non-residential buildings except for Class 2 and Class 3 buildings. Non-residential buildings not in these states (except for Class 2 and 3 buildings) are not covered by specified bushfire requirements, even in bushfire prone regions.
Addressing the issue of building and planning controls, Bergsma says that events of houses being destroyed in fires may not reflect present development and building controls, as the majority of these houses would have been built under controls that came before those mandated today.
She states that many residences lost in today’s bushfires have not been countryside properties situated in the bush, but urban properties in regional and local communities. In the majority of instances, these fires have struck outside of areas designated as bushfire prone.
Bergsma says further that we must take a look at factors that cause housefires in the first place. Some houses built beneath trees could be at risk, as leaves, litter and debris could act as fuel. And considering the proximity of houses in township areas, fires striking one home can also strike nearby properties.
Referencing construction methods and rules, Bergsma states that current BAL ratings place too much emphasis on building elements like material selection and do not give enough consideration to factors like roof design and the interaction of roofs and property in regards to the bush. She also states that BAL ratings place too much emphasis on the distance that the fire must go from the starting point of the bush to reach the house as opposed to the danger of residences being impacted by way of ember attack.
In the future, Bergsma wants a greater application of asset protection zones in rural communities and certain suburban regions. These are regions around critical assets or residences in which efforts to minimise fuel loads regarding to fires are undertaken.
In addition, an examination of buildings constructed in the wake of the Black Saturday bushfires should be conducted, to find out as to how lessons learned through the Royal Commission investigation into that fire are being applied in the construction of new structures.
More examination is needed into the causes of these fires. This would entail the identification of the portion lost due to ember attack, instead of direct bushfire contact with the side of the dwelling.
From this investigation could evolve a pair of future initiatives.
First, improved info and education could be supplied to citizens regarding how to ready themselves and their houses for potential fires. This could include advice regarding the reduction of fuel loads like leaf litter and debris.
Secondly, changes in the area of planning and vegetation could be considered, especially in regards to the sizable populations of gum trees in urban areas.
Douglas sees a need for the expansion of building types protected by particular bushfire-related measures in building design. He believes that protection measures should be applied to hospitals, schools and other structures that cater to vulnerable people. And he says that portions of Class 4 buildings that are residential in purpose should be protected.
In addition, particular measures are required to lower fuel loads in and around buildings and houses, and not necessarily on surrounding natural areas. Since many favour tree-lined properties, features like gutter or valley guards for buildings should be required in areas with trees. So should the application of non-combustible sarking materials in walls in roofs: presently, Douglas says that AS 3959 permits for sarking materials with a flammability index of less than five to be utilised. And, especially in homes rated in the lower BAL levels, more action must be taken to prevent embers from penetrating subfloor systems elevated off the ground. Presently, Douglas says that AS3959 permits the floor height to stand taller than 400 millimetres above the ground without protection. This, he states, not only empowers embers to penetrate the subfloor system but also promotes the use of subfloor space for storage. Potentially, this could fuel a fire. Specifications are required regarding the appropriate placement of LPG employed in rural and village areas so gas bottles do not cause fires and endanger homes.
Douglas also states that it is valuable to learn from past and present fires regarding how to enhance the design of subdivisions by way of fitting road networks and separation between urban and rural bushland areas.
Fourth, he states that we must employ innovative design strategies to reduce the risk of bushfires; solutions that integrate the urban form in a manner which ensures safety while maintaining the beauty of the area. And when selling properties, Douglas says that vendors should be called upon to guarantee that a property is compliant with all planning and building provisions in place, including the maintenance of asset protection zones and building standards.
And ultimately, designers and planners must be better educated on the matter of bushfire protection.