Very often there is more than one way to protect against each of the major bushfire hazards. In each case, it is wise to think about the practicalities of the solution and how it fits with your overall goals of how you want the house and garden to look and function.
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The design response
Generally, the more hazards you can avoid through siting and landscaping, the fewer that need to be addressed during construction (which can be expensive).
The most cost-effective approaches involve striking a balance between hazard minimisation through siting, and vulnerability minimisation through landscaping and construction.
Siting refers to the act of positioning your home on your lot or property. A related concept is called site layout, which refers to the process of appropriately positioning key elements (such as sheds, parking spaces and pathways) around the house.
Bushfire resilient construction involves planning and building homes (and other structures) using appropriate design principles and materials.
Similarly, bushfire resilient landscaping involves planning, selecting, and managing bushfire resilient plantings and other garden features in the area around the house.
There are multiple ways to manage the same hazard, using one or a combination of approaches, with some approaches being more viable than others. For example, to minimise the risk of ember attack you could add a separation distance of 700 meters between the home and the nearest sources of fuels. However it may be more practical to build using ember resistant construction materials and designs.
A different example to manage tree strike (falling trees and branches), you could either create a separation distance equal to at least one tree height between your home and the nearest tree, or build using heavy construction materials and methods. This latter option can be effective, but it can be prohibitively expensive for most builds.
Finding your best design
The following Design responses table will help you to optimise your design response to bushfire hazards. Bushfires can have a range of hazards that each vary in their difficulty to address. For each hazard, we note which of the major design responses (siting, construction, or landscaping) can best address the hazard, and describe why addressing the hazard is important.
The number of ticks indicates the suitability of the given design response. Two ticks √√ is best. A single tick √ indicates that the hazard can be mostly addressed by the given design response; however, the solution likely comes with drawbacks, either the solution only partially addresses the hazard (requiring other measures to cover the shortfall), or it does so at a significant financial cost. This financial cost is shown with a dollar sign, from $ indicating a relatively low financial cost, to $$$$ indicating a relatively high financial cost.
A design response without a dollar sign are inherently free, although there may be secondary costs or trade-offs involved depending on the situation. For example, minimising a hazard through siting does not incur a direct financial cost; however, you may need to clear existing structures or vegetation to make way for the new build at this best-case location, which will incur additional costs. These additional costs are not considered.
|Some costs involved||$|
|Not suitable or applicable||×|
|Flame from unmanaged (classified) vegetation||Unmanaged vegetation can ignite and spread fire, damaging or destroying buildings, vehicles, and other objects, and threatening the safety of people.||Site the home away from unmanaged vegetation.
Buildings can be constructed using non-flammable flame resilient materials, or the building can be underground as a bunker; however, both options (especially building underground) can be prohibitively expensive.
|Flame from fixed structures||Structures can burn for a long time, producing dangerous levels of heat and toxic smoke.||Site the home away from neighbouring buildings and other fixed structures.
Buildings can be constructed using non-flammable, flame resilient materials.
Consider non-combustible barriers (fences and earthworks).
|Flame from vehicles and other moveable objects||Vehicles can burn for a long time, producing moderate levels of heat and dangerous levels of toxic smoke.||Design your site layout so that vehicles are positioned away from the home, accessways and secondary places of shelter||×||√||√√ $|
|Tree strike||Tree strike (falling trees and branches) can damage or destroy buildings, spread fire, and injure, kill or trap people.||Site the home away from trees. Create a separation distance of at least 1.5 times the mature height of the tree.
Buildings can be constructed to withstand tree strike, using heavy construction materials; however appropriate designs can be extremely expensive to build, and elements of the building such as windows are likely to remain vulnerable.
|Radiant heat from burning vegetation||Radiant heat can dry out, pre-heat and ignite, buildings and garden vegetation.||Site the home away from vegetation.
Buildings can be constructed using non-combustible materials.
Consider non-combustible barriers (fences and earthworks) to reduce the impact from radiant heat.
|Radiant heat from burning vegetation burning (below 29kW/m2)||Radiant heat can dry out, pre-heat and ignite vehicles, buildings and vegetation.||Site the home away from vegetation. Radiant heat can also be addressed using non-combustible barriers (such as fences) and earthworks (such as retaining walls).
Use construction material and design to avoid ignition.
|√||√ $||√ $|
|Radiant heat from burning structures||Radiant heat can dry out, pre-heat and ignite, buildings and vegetation.||Site the home away from neighbouring buildings and other fixed structures. Radiant heat can also be addressed using non-combustible barriers (e.g., fences) and earthworks (e.g., retaining walls).
Buildings can be constructed using non-combustible materials.
Consider non-combustible barriers (fences and earthworks) between buildings.
|√√||√ $$||√ $|
|Radiant heat from vehicles and other moveable objects||Radiant heat can dry out, pre-heat buildings and vegetation, making them easier to ignite.||Design your site layout so that vehicles are positioned away from the home, accessways and secondary places of shelter
Radiant heat can also be addressed using non-combustible barriers (such as fences) and earthworks (such as retaining walls).
|×||√ $||√√ $|
|Wind attack||Wind can carry embers and burning debris which can ignite vehicles, buildings and vegetation. Strong Wind (greater than 75kmh) alone can fell trees, damage buildings, and threaten the movement of people.||Site the house in an area of the property with low wind exposure.
Use construction measures to consider designing for additional wind loading.
Use appropriately placed hedges and other screening plants to lower wind exposure.
Non-combustible barriers can lower wind exposure (fences and earthworks).
|√||√√ $$||√ $|
|Ember attack||Embers and burning debris are a main source of ignition and can attack buildings, vegetation and other elements ahead of the fire front or long after it has passed.||Ember protection is best achieved at the house level using construction material and design to avoid gaps that allow ember entry and building designs that encourage ember to accumulate near the vulnerable parts of the building.
Consider using appropriately placed hedges and other screening plants to filter embers and wind-driven debris. Non-combustible barriers, such as fences and earthworks, can also protect the house from embers.
|Smoke exposure||Smoke, including toxic gases, can worsen asthma and other respiratory conditions, irritate the eyes, nose and throat and cause coughing, shortness of breath or suffocation. Finer particles can penetrate deep into the lungs and cause long-term health problems.||Best achieved at the house level, having a house sealed for ember attack will also reduce smoke entry||×||√√ $||×|
|Surface fire||Surface fires move through grasses, forest litter, mulch and bark garden beds. These fires have short flame lengths (below your knee) and can impact buildings, vehicles and vegetation elements at that level. They can also provide significant radiant heat to building elements at higher levels||Create an open space (with non-combustible surfaces) around the home.
Break up large or continuous areas of lawn and cut grasses with non-combustible surfaces such as paths and driveways.
Avoid dense plantings of shrubs – plant individual or small clusters of shrubs separated by breaks.
Use non-combustible mulches.