Bushfire Attack Level (BAL) Assessments

With the anniversary of the devastating Victorian Black Saturday bushfires this weekend, I thought it timely to share my experiences volunteering to assist Kinglake residents with their Bushfire Attack Level (BAL) Assessments – the first step in their rebuilding process.

Bushfire Attack Level (BAL) Assessments

After the devastating Victorian bushfires of February 2009, the State Government rapidly introduced a new residential building standard with increased fire protection construction requirements. I took the opportunity to participate in the Royal Building Commission industry seminars that informed building practitioners on the technical aspects of the new standards. As I didn’t grow up in Australia, the seminars were particularly interesting for me because they detailed not just the rebuilding process, but also about bushfires in general – their history, how and why they occur and how they spread.

In order to rebuild on sites affected by the bushfires, the new Victorian building standard requires a BAL (Bushfire Attack Level) Assessment on every new site in Victoria (whether in the affected Kinglake region or not).  This BAL Assessment determines the risk of fire damage of the subject site in the event of a bushfire and hence the additional construction methods required to protect the property. With my architectural background, I was fortunate to be one of the first who were able to volunteer with the Building Commission and help affected residents start the rebuilding process.

Visiting Kinglake

Although we’ve all now seen those bushfire pictures again and again on TV, it still felt incomprehensible and somehow surreal when I arrived on site. One can’t possibly understand the full extent of damage to life, land and property for those affected – and this was still months after the fires had long been extinguished. I have to admit, as I was approaching Kinglake, I was not prepared for what was awaiting me. The cruelty, unpredictability and randomness of how the fires destroyed one house and spared another…to see all the burned sites, the trees and how the survivors resided in their tiny caravans…I can’t put it in words, it was just overwhelming.

Altogether I did twelve assessments over four days, in Kinglake, Kinglake West, Humevale, Pheasant Creek and Whittlesea: twelve destroyed livelihoods, twelve different stories but nevertheless all twelve braving their fate and looking to rebuild.  Sometimes it was kind of spooky – thinking about the fact that some sites were so secluded – that during the fires one would have been so far away from any help. The region was so alien – scorched earth, stray (and in some cases, aggressive) dogs trying to guard their property, rusted shells of cars and appliances, hidden barbed wire, destroyed septic tanks and hundreds of burnt trees – swaying, creaking, ominous and scary above you.

But all of this is nothing compared to the people I encountered. Some were eager to tell their stories, others just taken aback. All with a sadness in their eyes that convey far more than any words could do.

In general, most of the affected properties I assessed ended up being BAL FZ. FZ stands for Flame Zone and means “direct exposure to flames from fire front in addition to heat flux and ember attack“. BAL-FZ represents the greatest possible risk of fire damage that a site can be situated in.

Surprisingly two properties I assessed ended up being BAL LOW, which means “there is insufficient risk to warrant specific construction requirements“.

The Bushfire Attack Level Assessment process

To understand the whole BAL Assessment process better, I’ll outline how we were instructed to assess a property.

Step One: Determine your Fire Danger Index (FDI)

The Fire Danger Index (FDI) is a measure of the probability of a bushfire starting. This factors, amongst other things, the rate of spread, intensity and difficulty of suppression according to various combinations of temperature, relative humidity, estimate of fuel state and so on.

The Australian Standard AS 3959-2009 identifies the FDI for all regions across Australia.

Step Two: Determine your site’s vegetation types

The Australian Standard AS 3959-2009 provides tables that set out visually and descriptively, seven types of vegetation classification.

Step Three: Determine the distance from the site to vegetation

After determining your site’s vegetation type, the next step is to determine the distance from your site to the vegetation itself. This is because the proximity of the vegetation to the building site will have an influence on the level of bushfire risk.

Step Four: Determine the slope of the land under the vegetation

The slope of the land towards the vegetation has a direct influence on the severity of a bushfire. Bushfires have a tendency to move uphill more rapidly than downhill.

Step Five: Determine the BAL

To determine the BAL one enters the Fire Danger Index (FDI), vegetation types, distances and slopes into a given table in the Australian Standard AS 3959-2009.

Step Six: Apply the construction requirements as set out in the Australian Standard

Now you can apply the construction requirements as set out in the Australian Standard AS 3959-2009 that correspond to the BAL that you have determined.

Conclusion

Summing up I have to say, the new Australian Standard is a good start, but it would probably be impossible to come up with a standard that anticipated every potential aspect.

I would strongly recommend: protect your home against ember attack, especially when you live in a bushfire prone area. Keep in mind that embers can travel extremely long distances particularly under rough wind conditions and can ignite even after many hours.

Even when you take every precaution to protect your home, it will not guarantee that a building will survive a fire due to the unpredictability and often devastating nature of bushfires – leaving early is always the safest option.

For further details about the Bushfire Attack Levels, Assessments and/or how to protect your house against ember attack, burning debris and exposure to flames please talk to your architect or building designer.

ARE YOU REBUILDING?
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from Simone’s BAL Assessment experience!

Useful links

• View more of my Bushfire Attack Level (BAL) Assessment photos online
• Read my earlier article detailing the Victorian Bushfire Attack Levels (BALs)
• Building Commission of Victoria’s Guide to assessing your property’s Bushfire Attack Level
• Purchase Australian Standards’ AS 3959-2009 incorporating BALs
• Victorian Bushfire Reconstruction & Recovery Authority Bushfire Rebuilding Frequently Asked Questions
• Brutal Art Design + Build Staff Profile: Ms Simone Schenkel

Related posts:

1. The new Victorian Bushfire Attack Levels (BALs)
2. Staff Profile: Ms Simone Schenkel
3. Property Development 101: Step 5
4. Property Development 101: Introduction
5. Property Development 101: Step 6

Tagged as: Architecture + Design, Building, Building Commission, Building Permit, Bushfire Attack Levels (BALs), Melbourne, Surveyor, Victoria