Dr Ian Weir is a consulting research architect with the Queensland University of Technology and director of Ian Weir Architect. In both roles he receives commissions for designing bushfire responsive houses which over the past few years has included the widely circulated Karri Fire House, which he designed in collaboration with Kylie Feher, and H House, both in Western Australia. He is also a member of the Bushfire Building Council of Australia.
The below conversation between Architecture & Design Editor Nathan Johnson and Weir discusses the major challenges and misconceptions associated with designing bushfire-responsive housing and explores design strategies for achieving compliant housing in high Bushfire Attack Level (BAL) areas without the need for incessant vegetation clearing.
Nathan Johnson: So we’ll start by exploring the major misconceptions associated with designing affordable bushfire-responsive housing in both the public and the industry. What are they and where do you think they derive?
Ian Weir: There are three main misconceptions that I have encountered while working in my practice and I can break them down for you.
1. Cost
- Landowners think it will be cheaper and more effective to clear vegetation rather than build a bushfire responsive house, not realising that the greatest threat to houses in bushfire is ember attack which can come from many kilometres away, and furthermore the vegetation has to be managed in perpetuity so there is a real cost in time and money in doing that.
- When rebuilding after bushfire, owners think that the greatest contribution to cost will be compliance with the bushfire regulations, but more often than not it is all the other requirements that have been introduced since their initial home was built such as: energy efficiency; structural adequacy; glazing standards etc.
- The affordable home market and the Bushfire standard (AS3959) are not in opposition. For example, the typical first home-owner ‘project home’ in WA is already well prepared for bushfire, with double brick walls, slab on ground and metal clad roofs. This is the cheapest home to build in WA and for an extra $2,000-3,000 (less than 1 per cent) that home could comply with BAL-40 - the second highest resilience level in AS3959. The cheapest wall system to build for one-off construction in Australia is a light timber of steel frame clad in steel sheet and that also complies with BAL-40.
- The published costs on the premiums associated with building to the various Bushfire Attack Levels (BAL’s) - which we find on various websites – a based on the difference in cost to a conventional timber framed house. That house typology is not representative of what we typically build in Australia to satisfy the first home buyers’ market (as per ‘c’ above)
2. Belief that houses can’t survive bushfires:
- Many people in the community, and even in the architectural fraternity, believe that no matter what you build it will not survive the intensity of a bushfire. I attribute this misconception to images of houses with molten glass and aluminium that have been subjected not to bushfires but rather to structural fires where heat intensities are much greater and more sustained than typical bushfire fronts.
3. Resale value
- Land owners believe that it is better to build to a lower BAL rather than a higher BAL because they think it will affect the resale value of the home and/or attract higher insurance premiums. I have experienced this pressure from clients in my architecture practice.
NJ: You advocate for highly quality integrated or ‘multi-modal’ designs for bushfire prone areas; designs that achieve meaningful and practical solutions for the raft of issues presented by these landscapes: heat/cold, fire protection and context. What do you mean by this and can you give us an example where you’ve used this?
IW: Building in bushfire prone areas often attracts a premium anyway (regardless of the bushfire regulations) due to the difficulty of access, steep terrain, remote locations need for off-grid power and water systems. Furthermore, bushfire prone areas, by their nature, are both hot in summer and cold in winter, so achieving energy efficiency can be costly. The key to mitigating these high costs therefore is to ‘cross-purpose’ all these constraints so that building elements achieve more than one thing.
By way of example the Karri Fire House has the following features, remembering that it was built by the owner not a registered builder (to save cost):
- Steel structural frame manufactured off-site and assembled by an expert team, does many things: saves cost and time for the owner builder; adds precision to the project; negotiates the steep terrain (15 degrees); galvanised against coastal corrosion; supports the cantilevered verandah and the suspended concrete floors while is also BAL-40 compliant and non- combustible.
- Suspended concrete floor is cast in place to 190mm thick. It adds necessary thermal mass for 6 star energy rating, and is of course is fire proof.
- Concrete block cavity wall (south side) adds to thermal mass, owner built, and fire proof.
- Metal cladding (roof and walls) is ‘galvabond’ galvanised sheet (thicker than normal) provides first line of defence to heat and embers, is cheap and easy to install and BAL-40 compliant. Aesthetically it harmonises with the galvanised structural steel elements as well as the surrounding granite outcrops.
- Ember screens are insect screens in this insect prone landscape such screens are required anyway, here they are stainless steel and slide in unison with sliding glass doors on the veranda elevation. They are retrofitting into commercial sliding door tracks to provide a very cost affordable solution to ember protection and insect screening (It is lightweight Stainless Steel – a heavier gauge would also provide security).
Addressing a ‘national problem’: Karri Fire House by Ian Weir and Kylie Feher Architect is both a model for affordable bushfire response architecture and as a model for good design in lieu of incessant vegetation clearing in bushfire-prone areas
NJ: What then are the major impediments to this approach?
IW: All the assumptions, prejudices, misconceptions I mentioned before.
- A tick-the-box approach to compliance by the architectural and building design industry.
- That the majority of homes in Australia are not designed by architects but by drafts people in building companies and often AS3959 considerations only appear in the specification (IE “Must be built to AS3959”) and not in the drawings so AS3959 compliance mostly doesn’t get designed in at all – instead it effectively gets retrofitted to the design by the builder .
- That AS3959 compliance discussions most commonly only occur at the Building Permit stage when it is too late to apply and integrated design approach. This should happen more at the Pre-Planning Approval stage. For example, I always meet with the Local Government Building Surveyor and the town planner before lodging the planning application.
NJ: There is a tendency from authorities to prefer clearance of vegetation and the construction of homes with mid-range BAL level features. What troubles can this create?
IW: Local Governments want uniformity (e.g. everyone must have a 20 metre asset protection zone (APZ) around their house) and they want the least drain on their resources to inspect and administer variations and special cases. But principally, my view is that they want to be exonerated from liability.
The problem is that the professed aim – from fire authorities and the risk assessment experts worldwide – is that people should understand their risk and mitigate against it – that we each take responsibility for our patch and not expect emergency services to save us. This makes sense.
But by mandating 20 metre APZs through legislation—as is being done in WA – where if the clearing is not done the land owner is fined and the LG does the work and sends the landowner the bill – that very aim for personal responsibility is completely undermined, it becomes a top-down authoritative relationship – it is completely contradictory to the aim.
The bushfire prone landscape is a landscape which is highly variable in topography, subdivision patterns and vegetation types, so a uniform approach just cannot be applied – especially to existing subdivided land.
Meanwhile, there is considerable inconsistency across Australia and between authorities within states as to how vegetation should be managed in APZs and as to what the exact purpose of them are. AS3959 for example does not mention APZs – it is primarily concerned with fuel loads, while the CSIRO report that trees can be a very good thing close to houses because they reduce wind velocity and shield houses from ember attack.
H House by Ian Weir Architect is built for a family of five in the bushfire prone biodiverse landscape of Point Henry, Western Australia. According to Weir, the house was not designed to be a bushfire resistant house per se, but to be a place that would situate the owners in close proximity to the diverse health vegetation of the site.
NJ: So do you think architects can play a reconciling role in these otherwise opposing management goals of bushfire safety and biodiversity conservation?
IW: Well absolutely, and to do that that we (architects, designers and innovators) need to not just think of balancing vegetation clearing with more resilient house designs but to instead – here I borrow Noel Pearson’s term – find the ‘radical centre’. That is, develop new typologies of architecture that celebrate our inhabitation of this landscape which is at once highly biodiverse and bushfire prone.
NJ: So what are the major challenges associated with actual designing of BAL40 and BALFZ houses, and how can we overcome them?
IW: Strictly for BAL-FZ a big hindrance is the lack of competitively priced and alternative types of bushfire shutter systems. In general, it’s because AS3959 is considered the ceiling when it should be considered the floor.
The NCC says that we don’t need to comply with AS3959 we need to comply with the performance requirements first and AS3959 is just one of the ways of doing that (The NASH standard is another DTS method). So we architects and building designers need to work more closely with fire engineers and building certifiers to devise performance based-solutions, because ultimately AS3959 is just a base line which is devised to be acceptable and affordable to the broad community, it is in no way the best practice of what we could be doing to make homes and communities more resilient.
NJ: Is the technology on the market to facilitate this? Is it difficult to come by?
IW: The fire safety requirements in the commercial building industry have already triggered the development of building elements that surpass the requirements for bushfire resilience. Houses are pretty basic things, it is just the selection of materials and how they are put together, so new technology as such is not the solution. What we need is more lateral thinking and greater access to affordable fire testing facilities to demonstrate the performance compliance of new elements.
