What is Defensible Space and Why is it Necessary
Defensible space is one strategy for fire control. It is a natural and/or landscaped area around a structure designed to reduce the risk of fire spreading to your house or outbuildings. Defensible space provides a safer area for firefighters from which to defend your property. Firefighters need to prioritize their efforts as to which homes to try to save. If you do not have defensible space, and your neighbor does, they will go to your neighbor’s house first because it is a safer space for them to work in.
How to Create Defensible Space
The most important aspect of defensible space is fuel reduction. The California Fire Safe Council suggests that there be nothing ignitable within the first 5 feet of your structures, and reduced fuels out to 100 feet or the property line, whichever is closer.
There are three zones to be considered when creating your defensible space.
ZONE 0 – This is 0 to 5 feet from buildings, decks, and other structures. The purpose of Zone 0 is to prevent embers from reaching your house. In this zone, you want to use materials that are noncombustible such as stone, rock, cement, bare earth, gravel, and sand. These materials are all resistant to embers that are the biggest cause of spreading flames. In Zone 0 you want to clear and remove anything that is combustible which means all plants and shrubs, leaves and needles from the ground, and from your roof, gutters and under decks, cut back branches that touch your roof or chimney to 10 feet. The basic rule of thumb in Zone 0 is to have it as cleared out as possible. Do not store anything flammable under your decks such as old paint or chemicals of any kind. Also, do not store firewood near your house or other structures.
ZONE 1 – This Zone is 5 to 30 feet from buildings, decks, and other structures. In this zone the purpose of the work you do is to reduce heat and the spread of flames. In this zone you need to rake leaves, needles, twigs, bark, and smaller branches to a depth of two inches. Thin and prune plants and shrubs to break up the more continuous and dense layers of vegetation. If you have a garden in this zone, do not use too much mulch because that can help fire spread. You also want to move any gas and propane tanks outside of this zone and do not store firewood in this zone either.
ZONE 2 – This Zone includes the entire rest of your property, to 100 feet from buildings, decks, and other structures. The purpose of this zone is to create horizontal space between shrubs and trees, and create vertical space between grass, shrubs, and trees. You want to avoid a “fuel ladder”. Like rungs on a ladder, vegetation can be present at varying heights from ground cover to trees. Ground fuel “rungs”, such as dried grasses, can transmit fire to shrub rungs, which then transmit up tree branch rungs into the tree canopy. A burning tree produces embers that can blow to new areas, spreading and making it more difficult to control a wild-land fire. One guideline is for a typical separation of three times the height of the lower fuel to the next fuel ladder. For example, a 2-foot-high shrub under a tree would need a spacing of 6 feet to the lowest limbs of the tree. Since wildfires burn faster uphill than on flat land, fuel ladder spacing may need to be greater for slopes.
It is important to get advice from a landscaper or the fire department when creating your defensible space, so you do not unintentionally create negative consequences such as erosion and loss of native habitat. The disturbance of the soil surface, such as garden soil cultivation and firebreaks beyond native landscape areas, destroys native plant cover and exposes open soil, accelerating invasive species of “exotics” spreading and replacing native habitats. Negative aesthetic consequences to natural and landscaped areas can be minimized with integrated and balanced defensible space practices.
What to Do Prior to Evacuation
If you get orders to evacuate, you want to pull patio furniture, play sets, table umbrellas, and gas BBQ tanks as far as possible from any structure, and bring the cushions and other small items inside.
For more in-depth information, please go to FireSafeCouncil.org.