The way fire ignites and spreads (the fire behaviour) is controlled by the three elements:
You don’t have any influence over the weather and topography. But you CAN manage the fuel around your home.
So we’ve compiled a few critical and achievable actions that you, as a homeowner, can take to reduce the risk of wildfire damaging your home (these are taken from Canada’s FireSmart: Protecting Your Community from Wildfire – Second Edition).
FACTOR 1 – ROOF AND GUTTER CLEANLINESS
A build-up of combustible debris, like leaves on a roof, increases fire risk. The fire resistance of most roofing materials reduces when piles of leaves or other debris burn on or near the roof surface, rafters or beams.
FACTOR 2 - EAVES, VENTS AND OPENINGS
Vents have an important function: to remove trapped moisture from attics, crawlspaces and the underside of arches and balconies. But they are also ready-made openings that allow heat and embers to enter a building and ignite it. Open eaves (these are the edge of a roof where there is a pronounced overhang) increase structural fire danger because more of the under-eave area is exposed to heat and embers.
Vents in the under-eave area that are placed close to the exterior wall also increase structural fire hazard. That’s because heat and embers travel up exterior walls and directly into vents in the overhangs. You should ideally find these openings and screen them with corrosion-resistant, 3-millimetre wire mesh.
FACTOR 3 – FIND YOUR NEARBY COMBUSTIBLES
Firewood, building material (and other combustible debris piles), neighbouring buildings and wooden wendy houses, lapas or storage shacks are all serious fire dangers. These will ignite and burn intensely. Homeowners often don’t consider the potential fire danger of these items and should be encouraged to clean up or move these fuel loads further from your main building.
Where combustibles are found downslope from a building, the hazard to buildings increases. Research shows us that neighbouring structures are a major potential ignition source, because of radiant heat exposure, longer burning times and the additional risk to the building from firebrands produced by nearby burning structures.
FACTOR 4 – FOREST VEGETATION (OVERSTORY)
Crown fire in forest vegetation presents a significant threat to adjacent buildings. Buildings may ignite simply by radiant heat transfer when the fire is burning all around it, or when firebrands or embers land on the building before the wildfire arrives.
You’ll find that crown fire most likely occurs and spreads rapidly in dense alien tree forests. Indigenous mixed-wood forests are less likely to sustain crown fire. The probability (excluding in extreme fires) of fire spreading laterally from crown to crown is much less when highly combustible trees like pines, eucalyptus or acacia trees are spaced far apart.
FACTOR 5 – SURFACE VEGETATION
Surface vegetation includes grasses, bushes, shrubs, dead woody debris that has fallen to the ground (logs, branches, and twigs), and immature trees up to 2.5 metres in height. Areas where there are a lot of surface fuels will sustain high-intensity surface fires and can start crown fires.
Dry surface fuels are a particular worry when vegetation is dried due to drought or seasonal effects. A surface fire can ignite interface buildings by direct contact with the building exterior or nearby flammable materials. Untreated surface fuels can also support and spread small accidental ignitions from the site to the surrounding veld.
FACTOR 6 – LADDER FUELS
Ladder fuels are shrubs, immature trees, and branches extending near the ground (e.g. within 2 metres) that give surface fires a pathway to the upper canopies of trees. Trees with branches extending near the ground (within 2 meters) have ladder fuels. You should ideally remove these ladder fuels to reduce the likelihood of crown fire starting. In practice this means you should remove or severely thin out all branches from ground level up to 2 meters from trees, etc.
For the full list please click here: www.firesmartcanada.ca.