Protecting your home during the bushfire season

Protecting your home during the bushfire season

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The 2019/20 bushfire season was like no other Australians had ever experienced. Fuelled by high winds, extremely dry conditions and searing temperatures, raging fires decimated more than 46 million acres of bushland, claimed 33 lives, killed billions of native wildlife and destroyed more than 3000 homes

Longer hotter summers and drier winters, along with more people living on the fringe of national parks and parcels of bushland, are among the factors putting more Australians and their homes at risk.

Kate Cotter, CEO of the Bushfire Building Council of Australia, says many homes are literally in the line of fire. “There are one million properties within 100m of bushland, and this is where 85 per cent of our losses occur,” she says.

At least 90 per cent of properties in bushfire-prone regions have not been built to bushfire standards and of the 10 per cent that have, it’s estimated from building loss surveys that 50 per cent are either non-compliant, aren’t maintained to standard or are exposed to risks not covered by regulation (such as house-to-house ignition).

Bushfires destroy homes in several ways, including through direct flame contact, radiant heat, and/or burning embers. Justin Leonard, research leader of bushfire adaptation at the CSIRO, says more than 90 per cent of homes lost in past bushfires burnt down without being affected by a large bushfire front or the radiation from it. “They’re ignited by a combination of ember attack and low-level surface fire that either directly ignites the house or ignites adjacent features that then ignite the house,” he explains.

Justin says reducing risk factors starts with being proactive by getting a qualified fire assessor to determine your site risk level. Architect Rob Brown, from Casey Brown Architecture, says it can be a complex process to assess risk levels, which is why homeowners need to get a professional onboard.

“A bushfire consultant will look at things such as the region where you live, assess your asset protection zone, the slope and aspect of the house, and surrounding vegetation,” he says. “Everything is specific to the risk and circumstances of the particular site.”

The Australian Standards AS3959 has different classifications or Bushfire Attack Levels (BALs), which determine the risk of fire threat. This ranges from BAL-Low to BAL-12.5, BAL-19, BAL-29, BAL-40 and BAL-FZ (flame zone). The higher the rating, the more that’s required in building safeguard measures to reduce fire threat.

But Australian fire experts like Kate don’t believe these measures are stringent enough. “With this system, if you have a BAL-Low rating, timber cladding is still allowed and I don’t believe you should use combustibles on the outside of a house,” she says.

Dr Ian Weir, research architect and senior lecturer in Landscape Architecture at QUT’s School of Design, concurs: “I believe the extraordinary biodiversity of Australia’s bushfire-prone landscapes should be the driver for design innovation rather than land clearing,” he says. Using an holistic design approach (incorporating landscape, architecture and industrial design processes), bushfire features are integrated into his designs in such a way that they can be used on a daily basis rather than just once in an emergency. Working on the principle that homes should be able to defend themselves against fire, the buildings his company designs exceed the minimum requirements of AS3959.

Justin also believes there’s still much work to be done. One of the critical issues he sees is the sense of disconnectedness people have from natural processes such as fire that shape the landscape. “This disconnection means there’s often a lack of personal responsibility to understand and adapt to these processes,” he says. “This often leads to homeowners choosing a minimum compliance path through the regulation processes and assuming that this adequately resolves the risk or issue.”

If building in a fire risk zone, Justin says it’s vital to learn as much as possible about fire behaviour, vegetation response to fire, and building performance in fires. “The way a homeowner builds and maintains their home, maintains the surrounding landscape and responds during a fire event are all critical to managing fire risk,” he emphasises.

There are many things you can do to reduce the risks, some of which are relatively simple. Kate recommends to first remove all combustibles within 10m of the house. “This includes mulch, vegetation, plastic water tanks, and on high-risk days put outdoor furniture, shoes and door mats inside,” she says. “The second thing is seal up any gaps, which can be done with a $20 bottle of silicone.”

Protecting your home during the bushfire season
A GROWING CONCERN

If you live in a bushfire-prone area, technological advancements in materials, plus research into safer building methods and construction practices, are helping to build more fire-resilient homes. And you don’t have to live in a cement bunker (though they can be cool). There are plenty of striking architecturally designed homes built with fire safety in mind.

Protecting your home during the bushfire seasonKate says no matter what the design, the key is to not build with combustible materials. “You also need a well-sealed secure roof with a wind load that’s higher than legal requirement,” she says. “And include ember guards where you want air flow. For example, with a timber sub floor we recommend steel mesh with a small aperture (1.8mL holes); air can flow through, but embers can’t get in.”

Earth walls, double brick and concrete walls are excellent choices, as are steel framing, choosing steel roofing over tiles and, if you’re building with timber, opting for more fire-resistant timbers such as blackbutt and spotted gum.

If a fire does breach the security of the home’s exterior, Kate says there are some design principles which, if applied in the home’s construction, give those inside more time to flee. “These include multiple exits out of one room so people don’t become trapped,” she says, “and fire separation walls in the roof cavity buys you more time if the roof ignites. You also need a place that offers shielding if a fire approaches, such as a non-combustible deck and supports, which can be made of fibre-cement material and should contain no plastics or timber.”

Many potentially dangerous hazards seem innocent enough, until a fire is in the vicinity. “If you have a plastic rubbish bin sitting alongside your house and the plastic melts, it will burn hot enough to ignite your home’s cladding,” Kate warns. “Polycarbonate roofing can also melt and set timber decking on fire.”

With gas bottles, you should be careful in which direction the pressure release valve faces. Having a reticulated supply, a tank suitable for firefighter access, and pump and hose connected are also important.

Despite all the concerns, it’s still possible to build a stylish and functional home with fire safety in mind. Rob says enlisting the guidance of an architect who’s well versed in building for fire safety is definitely a step in the right direction.

“The architect’s job is to incorporate all of the guidelines and the recommendations from the consultant’s report, taking into consideration the financial cost, the aesthetics of the building, how it fits with the owner’s lifestyle, and how it maximises the inherent potential and qualities of the site,” he says. “The aim is to create a home that for 99.9 per cent of the time is comfortably liveable and feels connected to the environment so the owners can enjoy it — but if a bushfire comes, they’ll be prepared.”

One project Rob’s company designed had a national park surrounding the site on three sides. It was classed as BL-FZ (flame zone) — the highest rating — but it had a water frontage so a lesser fire risk (BAL-40) was applied to the front of the home. “Basically, there’s an inner house made of timber, and outside that was the metal sheeting and shutters. The space between contained the verandahs and decks,” he says. In the case of a fire, the metal shutters could completely close it off.

Nothing flammable was used on the flame sides while at the front water side, where the views are, there’s an open deck, which also has fire shutters and fire glass. “We used Corten steel, which achieves a rusty red colour,” Rob explains. “It contrasts with the rest of the building, which is black, so there’s an aesthetic, as well as a functional response to the fire risk.” The roof is metal, there are water tanks dedicated for firefighters to use if needed, and major trees are cleared within the asset protection zone.

POSITIONING

Protecting your home during the bushfire seasonAnother project example Rob designed was a double-brick home with a metal roof. “It was located by the ocean and was exposed to the great southern storms,” he says. “It posed a different fire threat and was located in a more suburban area.” This home was classed as BAL-29 and BAL-FZ and they were able to use custom BAL-29 timber windows with specialty timber, glass and a tight seal. “In this case it was more about subtlety and locating the building away from the potential threat,” he says. “Also, different functions of the house which weren’t critical to living (such as the garage, for example) were positioned in the flame zone area.”

There are many other home styles that can be built with fire safety in mind, some of which are design triumphs. Sean O’Bryan, from Baldwin O’Bryan Architects, has designed eco-friendly and affordable fire-resistant houses (that can be built for about $1500 a square metre) constructed from stabilised compressed earth blocks. “It’s a high-volume low-cost solution designed specifically for where the threat of bushfire exists,” Sean says.

The building envelope design is super-resistant to ember attack. “There are no valleys, gutters or under-storeys to the building and no ridgeline, so nothing the embers can get underneath,” he explains. If fire does sweep through the area, magnesium oxide panels and shutters completely isolate the building from the fire.

Looking at the bigger picture, governments and organisations are continuing to work together to pave the way for smoother processes to improve fire safety around construction. With more education, and homeowners subsequently taking ownership of and embracing these new practices, mankind and nature can continue to live in harmony with each other.

Want to learn more about protecting your home from bushfires? Check out our bushfire archive.