Defensible Space Zones

Your defensible space is comprised of three zones. The selection and maintenance of vegetation and other combustible items in these zones will determine how adequate your defensible space is.

ZONE 1

0–5 ft and under the entire footprint of the entire deck

WHAT YOU SHOULD KNOW

The objective of this zone is to reduce the chance that ignition will occur near your home or business, resulting in a direct flame contact exposure to the building. Because this zone is closest to your home or business, it requires the most careful selection and intensive management of vegetation and materials.

WHAT YOU SHOULD DO

Install hard surfaces in this zone (e.g., concrete walkway) or use noncombustible mulch products (e.g., rock mulch). Landscape vegetation recommended for this zone includes irrigated lawn and low-growing herbaceous (non-woody) plants. Shrubs and trees, particularly conifers, are not recommended for use in this zone. Remov­e dead plant material from plants. Plants adjacent to combustible siding and foundation vents, as well as plants under or next to windows and under-eave vents or in interior corners present the greatest hazard.

ZONE 2

5–30 ft (or to the property line)

WHAT YOU SHOULD KNOW

The objective of vegetation management in this zone is to prevent the fire from climbing into the crown or upper portions of trees or shrubs and to stop any fire from burning directly to your home.

Wind-blown embers will still be able to ignite individual islands of plants in this zone, and that is why plant selection and maintenance is so critical in the 0–5 foot zone. This is also why spacing of vegetation is important in this zone.

WHAT YOU SHOULD DO

Place trees and shrubs in well-spaced groupings and keep them main­tained. Eliminating ladder fuels and creating separation between plants or plant groupings are techniques used to fulfill this objective.

Create islands or groupings of vegetation to form a discontinuous path of vegetation to make it difficult for the fire to burn directly to your home. Remove dead material and lower tree branches, and shrubs positioned under trees so that a surface fire cannot ignite vegetation what will allow fire to spread into the tree crown. This is often referred to as removing ladder fuels. Remove dead plant material and tree branches from vegetation on a regular maintenance schedule.

Maintain trees by keeping a minimum horizontal spacing of 10 feet between crowns, with the distance increasing with increasing slope. Prune limbs and branches to a height of up to 15 feet. For shorter trees, pruning should not exceed 1/3 of the tree height.

ZONE 3

30–100 ft (or to the property line)

WHAT YOU SHOULD KNOW

The objective of vegetation management in this zone is to slow down and reduce the energy of the wildfire, slowing its advance to your home. Tree and brush spacing should force any fire in the tops of the trees, brush or shrubs to drop to the ground.

The rate of spread and flame length of a wildfire is affected by slope. A steeper slope will result in a faster-moving fire with longer flame lengths.

WHAT YOU SHOULD DO

Remove dead plant material and tree branches from vegetation on a regular maintenance schedule. Creating islands or groupings of vegetation creates a discontinuous path of vegetation, thereby making it difficult for the fire to burn directly to your home. Lower tree branches and nearby shrubs (the ladder fuels) should be removed so that a surface fire cannot reach the tree crown. Maintain trees with a minimum horizontal spacing of 10 feet between crown edges, with adjustments as a function of slope. From the perspective of tree health, branch removal should not exceed 1/3 of the tree height.