A house destroyed by the Black Saturday bushfire, Yarra Glen

15 May 2013 — Sweet vs sour, bass vs treble, regulation vs free market, cost vs benefit. Balance is the key for many areas of life. But Dick Clarke suggests current standards have the balance wrong when it comes to building in bushfire-prone areas.

Building in bushfire-prone areas has always been a question of balancing the risk against the rewards: the risk of serious damage or even total annihilation against the benefit of connection with a bit of nature. The balance has changed since the rather hurried release and implementation of Australian Standard AS3959-2009 Construction of buildings in bushfire-prone areas (AS3959). That is, between freedom of design and choice in construction detailing, balanced against minimising risk of damage while offering a protective space in a fire event.

But has the right balance been struck? In conversations with some highly experienced bushfire consultants, and from my own experience of bushfire fighting and design going back to 1979, I will stick my neck out and say no. The pendulum swung too far following the tragic Victorian Black Saturday fires of 2009. I suggest that the regulatory impact statement prepared by the Australian Building Codes Board needs to be revised (see p.6 paragraph 27). The current standard provides no certainty of benefit, at significant cost.

Let me clarify a few things before the outrage begins. Fire hose in hand, I have stared down the barrel of the gun, and do not underestimate the ferocity and power of a major fire. It is terrifying, and anybody who tells you otherwise has not been there. I have designed houses in fire-prone areas, and been around to protect them successfully during fire events. I have worked with manufacturers to develop construction systems that assist in making buildings more defendable. In short, I understand the issues. However, I do not pretend to have all the answers. Here I am attempting to highlight problems with the current regulation and encourage all relevant parties – industry and expert consultants, CSIRO, ABCB and state planning technocrats – to have another look.

There are a number of assumptions in the underlying paradigm that have not been questioned.

Black Saturday bushfire near Wandong, Victoria

The occurrence of megafires

Black Saturday was a megafire: a fire of almost unimaginable ferocity and magnitude. There have been several megafires before, most notably in 1939 and 1983 – both in Victoria. There is no record of megafires prior to the 20th century, and indeed, the further back in Australia’s post-1788 history you look, the fewer and smaller the wildfires become. Bill Gammage’s headland 2011 book The Biggest Estate on Earth details why: fire was a tool used delicately, regularly and with great intelligence to farm the land by Aboriginal society, a significant byproduct of which was to maintain a landscape largely open and park-like, with a very low risk of large wildfires.

  • See Dick Clarke’s review of The Biggest Estate on Earth here

However, our notion of wilderness is now unbroken tracts of bushland with little if any management, which sets the background framework for an overarching assumption that uncontrolled bushfires will occur, and that big ones are unavoidably common. As climate change dries out the lower third of the continent, these will increasingly become megafires. I challenge the assumption that this situation is unavoidable. It was once managed successfully by Aboriginal people; it can be managed again.

Survivability in a megafire

Much of the intent of AS3959 has to do with providing a building that will protect the occupants for the duration of a fire front’s passing, usually less than 15 minutes. In moderate fires, this is a relatively achievable outcome, although no regulatory document guarantees this – that would be very brave indeed. Indeed, there is very little certainty that any structure can withstand the onslaught of a megafire. Radiant heat loads literally go off the scale, wind speeds exceed 120km/h, and flying debris make a firestorm akin to Armageddon.

A week or so after Black Saturday I inspected several areas on the fire grounds of Steel Creek and Clonbinane, Victoria, in the company of Mark Dunham of Rylock Windows.

Clonbinane is on the western edge of the megafire’s path, near to its point of ignition, and resembled many other burnt and partially burnt landscapes I have seen over the years. Steel Creek, however, like Kinglake, is near the eastern side of the great swathe, and faced the full force of the blaze. It was like nothing I have ever seen before: a moonscape, not a leaf on the ground, no twigs left on trees, trunks even deep in ravines snapped off at half height. Blue and white police tape still around so many houses, even of brick and stone, where charred bodies still lay, some clutching the remains of their fire hose. And yet here and there, survivors – still desperate to debrief and tell their stories.

How had some houses, and their occupants, survived? That was why we there – to try to figure it out. But in the end we could only conclude that a few got lucky.

Kinglake West after the Black Saturday bushfire

So what is the point of stringent BAL-FZ (Bushfire Attack Level-flame zone) construction requirements? The standard answer is that it increases the likelihood of survival. But if that likelihood is increased from zero to perhaps 50 per cent (and there are many who would not rate it that highly), is it just raising false hope? The best advice is surely to evacuate. The financial burden of BAL-40 and especially BAL-FZ construction detailing makes many houses unaffordable, in preparation for an event that may happen once in a decade or longer, or may never happen. This is in stark contrast to other regulatory requirements such as thermal performance, where the benefit applies nine months of the year, every year.

Perhaps we should look at the benefit of a complete reversal of “protection” and allow FZ buildings to be totally sacrificial, on the basis that in urban areas evacuation is by far the most sensible precaution. In non-urban areas, property owners could be given the option of having a bushfire shelter instead. Such buildings would necessarily be ultra-lightweight, with little material and energy debt. Good thermal performance can be achieved using organic insulation products and vegetable-based phase change materials.

Rigid and illogical risk assessment methodology

The third fault identified by expert consultants is the inflexibility of the BAL assessment methodology. Assessment factors are principally the locality’s fire danger index, the site’s topography, vegetation type and density. These are certainly the appropriate factors, but the method used does not anticipate all the unique variations that each site presents, and as there is no scope for expert variation one often gets self-evidently overstated BAL ratings.

The current method is a blunt instrument and must be revised to allow greater scope for expert consultants to offer the relevant consent authority a well-reasoned variation to the codified result. The NSW Rural Fire Service or the Country Fire Authority in Victoria would still have the opportunity to review the submitted rating and reject it if they have better information.

Conclusion

Fire is an essential part of Australia’s ecosystems, and an overhaul of how we think of it is long overdue. I suggest that the rather hurried introduction of AS3959’s revision in 2010 was at least partially a knee-jerk reaction by politicians and their mandarins who needed to be seen to be doing something. Hard research-based data, careful non-political consideration, and a mindset that questions the status quo are all essential ingredients to a more sustainable outcome.

We have no shortage of good hard data on fire behaviour in structures, and a great pool of evolving knowledge around bushfire behaviour. And we know with increasing certainty what climate change will mean for our bushland. What we need now is the last two ingredients: careful review, devoid of political grandstanding and posturing, and a nation-wide acknowledgement that our notion of pristine bushland and wilderness may be utterly misplaced.

This article is to be published in the Winter Edition of The Brief, the journal of Building Designers Australia.

Dick Clarke is director of Envirotecture, a design and sustainability consultancy based in Sydney, and is also sustainability director for Building Designers Australia.