Bunker-down the smart way in a bushfire

By Nick Kachel

The Black Saturday bushfires in Victoria 2009 are the worst fires in Australian history for loss of life. Of the 173 people who died, 113 were inside houses or other structures.

Personal bushfire bunkers were not common, and those that did exist were not regulated. Informal bunkers like shipping containers, cellars and self-built bunkers have been used during bushfires. Eight people died using informal bunkers.

Learning from loss

Our bushfire scientists visit non-active fire zones to survey the damage after a bushfire. They gather all types of data around bushfire behaviour, property damage, and loss of life.

In fact, we perform this important role of data collection in every major bushfire. We have performed this role since the Ash Wednesday fires of 1983.

After the 2009 fires, the Victorian Royal Commission provided recommendations. These inform a standard for bunkers and regulate the design, siting and construction.

The Victorian Country Fire Authority engaged us to provide science input. We also provided support in the development of policy guidelines.

This policy manages the siting and use of personal bunkers in bushfire protection. Our hope is by using scientific and engineering principles, we avoid tragic loss of life in the future.

Our recommendations

The Australian Building Codes Board engaged us based on our findings. We will assist in design, certification and correct construction.

Bushfire bunkers are built by certified builders across Australia. From the most recent bushfires, stories are now emerging of their use.

Watch our bushfire expert Justin Leonard talk about bushfire bunkers on The Project

Bunkers in bushfires

In this fire season, we know six instances in Victoria where individuals sheltered inside bunkers.

These bunkers were provided by accredited suppliers during burnovers of varying intensity. Burnovers occur when a fire overruns a location too fast for anyone to retreat.

In all six instances, no injuries or loss of life are on record, yet three of the six houses were destroyed. We are conducting more detailed investigations of these and other cases, to inform further design improvements.

What is a bushfire bunker?

Private bushfire bunkers are purpose-built structures to provide temporary shelter from a bushfire event. They can provide protection from direct flames, radiant heat and smoke.

Bunkers can be above or below ground, but are separate from a house.

The construction of bunkers

The location of a bushfire bunker and the surrounding property, are the primary influence in design and construction. The two main types of bunkers are:

above-ground bunker separate from an associated dwelling

in-ground shelter separate from an associated dwelling

Bushfire bunkers are separate structures, built six to 20 metres from adjacent houses and buildings. Using concrete or solid masonry, they are completely non-combustible. The bunker will not exceed 45 degrees over a 60-minute period.

For more information on bunker construction, visit the Australian Building Codes Board or CFA information page.

Can I rely on a bushfire bunker during a fire?

Use of a bunker is not without risk, and there is no guarantee it will save your life.

However, extreme caution must be taken when considering a private bunker in your bushfire plan.

It is not an alternative to leaving early and is not a stand-alone solution. However, it may inform part of your overall bushfire plan.

Does CSIRO provide accreditation for commercial bunker construction?

Accreditation is only provided by the Victorian Building Authority. Any commercial company that suggests we endorse its products is incorrect.

Where can I enquire about getting my own bunker?

Contact the Victorian Building Authority for a list of approved companies.