Seven steps to creating an effective defensible space:
The term “defensible space” refers to the area between a house and an oncoming wildfire where the vegetation has been managed to reduce the wildfire threat and allow firefighters to safely defend the house. In the event that firefighters are not available, defensible space also improves the likelihood of a house surviving without assistance.
Make your house safe for firefighters to defend.
Fortunately for Lake Tahoe Basin homeowners, there are a variety of resources available to assist them in creating defensible space. Local fire districts and departments will conduct free defensible space inspections. The Tahoe Basin Region of the Nevada Fire Safe Council can help organize your neighborhood to take action in reducing the wildfire threat and possibly fund defensible space projects. Advice on integrating defensible space practices with Best Management Practices (BMPs) and other landscape management topics can be provided by the Conservation Districts and Cooperative Extension in conjunction with the Tahoe Regional Planning Agency (TRPA) and fire professionals.
An effective defensible space can save your home.
The following seven steps describe how to create an effective defensible space.
Step 1: Determine the size of an effective defensible space.
Defensible space distance is measured from the base of the house, extending outward.
The first step is to determine the size of an effective defensible space. The size of the defensible space zone is usually expressed as a distance extending outward from the house in all directions.
The recommended distance is not the same for every home. It varies depending on the type of vegetation present and the steepness of slope surrounding the home. Use the “Defensible Space Zone Calculator” to determine the right distance for you.
Once the recommended distance for defensible space is known, mark it by tying strips of cloth or flagging to shrubs. This becomes the “Defensible Space Zone.”
If the defensible space zone exceeds your property boundaries, seek permission from adjacent landowners before doing work on their property (See Contact Information). It is important to note that the effectiveness of your defensible space improves when entire neighborhoods implement defensible space practices.
The next six steps apply to the vegetation growing within this area.
Step 2: Remove dead vegetation.
For the most part, dead vegetation should be removed from the Defensible Space Zone. Dead vegetation includes dead and dying standing trees or recently fallen trees; dead native and ornamental shrubs; dead branches; dried grass, weeds and flowers. Fallen trees embedded into the ground and located
more than 30 feet from the house can be left in place, with exposed branches removed.
Regarding fallen needles and leaves:
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Within 5 feet of the house, remove routinely throughout fire season.
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From 5 feet to 30 feet of the house, remove every spring by May 1.
Needles and leaves that fall after the spring removal period can
accumulate on the ground as long as they do not create a fire hazard.
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More than 30 feet from the house, do not allow fallen needles and
leaves to exceed a depth of 3 inches.
Step 3: Create a separation between shrubs and trees.
Before
After
Within the Defensible Space Zone, native trees and shrubs, such as Jeffrey pine, white fir, and manzanita should not occur in a dense stand. Dense stands of trees and shrubs pose a significant wildfire threat. Thin dense tree and shrub stands to create more space between them.
Dense shrub fields pose a significant fire threat.
Sagebrush, Manzanita, Huckleberry Oak, Other Shrubs: On flat to gently sloping terrain more than 30 feet from the house, individual shrubs or small clumps of shrubs within the Defensible Space Zone should be separated from one another by at least twice the height of the average shrub. For example, if the typical shrub height is 2 feet, there should be a separation between shrub branches of at least 4 feet. For homes located on steeper slopes, the separation distance should be greater. Remove shrubs or prune them to reduce their height and/or diameter. See Step 5 for shrub management recommendations within 30 feet of the house.
Forest Trees: On flat to gently sloping terrain more than 30 feet from the house, trees should be thinned to provide an average separation between the canopies of at least 10 feet. For homes located on steeper slopes, the separation distance should be greater. Within 30 feet of the house, tree canopies should be separated by 10 feet to 30 feet. Contact your local fire professionals or TRPA to have your trees evaluated and marked for removal.
Step 4: Remove ladder fuels.
Vegetation that can carry a fire burning in low-growing plants to taller plants is called “ladder fuel.” Lower tree branches should be removed to a height of at least 10 feet. Shrubs and trees growing under the drip line should also be removed. Irrigated, well-maintained lawn and flower beds, as well as low-growing native ground covers can be present under the tree’s drip line as long as they would not allow a fire to ignite the tree. Removal of tree branches should not exceed one third of the total tree height.
Remove ladder fuels to a height of 5 feet when no understory vegetation is present.
Vegetation that can carry fire from ground level into the tree branches is called "ladder fuel".
Step 5: Create a Lean, Clean and Green Area extending 5 feet to 30 feet from the house.
There are two goals for the Lean, Clean and Green Area. The first goal is to eliminate easily ignitable fuels, or “kindling,” near the house. This will help prevent embers from starting a fire in your yard. The second goal is to keep fire intensity low if it does ignite near the house. By proper management of the vegetation and other fuels near the house, a fire would not be able to generate enough heat to ignite the home.
For most homeowners, the Lean, Clean and Green Area is also the residential landscape. This area often has irrigation, is planted with ornamental vegetation, and is regularly maintained.
Erosion-control grasses and wildflowers are good choices for the Lean, Clean and Green Area. When dry, they should be mowed.
Lean, Clean and Green Area Tips
• Remove dead shrubs and trees; dried grass, flowers and weeds; dead branches; and firewood from this area.
• Remove fallen needles and leaves every spring by May 1.|
• Wood and bark mulches can be used in this area, but not in a widespread manner. Areas of wood and bark mulches should be separated by noncombustible materials, such as irrigated lawn, clover, erosion-control grasses and flowers, gravel, and rock, and arranged so that they would not allow a fire to travel rapidly across the area.
• Native shrubs should be substantially reduced in this area. Individual specimens or small groups can be retained as long as they are kept healthy and vigorous, pruned to reduce height and amount, and would not allow a fire to travel rapidly across the area. When removing shrubs, leave the root systems in place. Low-growing native shrubs, such as pinemat manzanita and Mahala mat, can be retained.
• Use low-growing (less than 18 inches tall), irrigated, herbaceous plants, such as lawn, clover, erosion-control grasses, flowers, some ground covers and succulents, that are recommended for the Lake Tahoe Basin.
• Ornamental, deciduous trees and shrubs can be used as specimens or in small groups. They should be irrigated, kept healthy and vigorous, free of dead leaves and wood, and arranged so that they could not rapidly transmit fire across the area. Deciduous trees should be placed so that their mature canopy can be easily maintained at a distance of at least 10 feet from other trees and the house. Shorter deciduous shrubs are preferred.
• Ornamental evergreen shrubs and trees, such as juniper, mugo pine, Austrian pine and others, should not be used within this area.
• Clear all flammable vegetation from within 10 feet of the propane tank.
• Remove tree limbs that are within 10 feet of the chimney, house, deck and roof. Remove limbs that are encroaching on power lines.
Step 6: Create a Noncombustible Area at least 5 feet wide around the base of the house.
The area immediately adjacent to a house is of critical importance to house survival during a wildfire. It should consist of noncombustible landscape materials and ignition-resistant, low-volume plants.
During a wildfire, airborne embers may land and accumulate in the area next to the house. Avoid using combustible materials, such as wood mulch, and flammable plants, such as juniper, within 5 feet of the home.
Photo courtesy of Mike Dannenberg.
Noncombustible Area Tips
• Remove dead shrubs and trees; dried grass, flowers and weeds; dead branches; and firewood from this area.
• Routinely remove fallen needles and leaves.
• Do not use bark and wood mulches.
• Do not use wood landscape timbers or boards.
• Remove flammable shrubs and trees. This includes native plants, such as big sagebrush, bitterbrush, greenleaf manzanita, snowbrush, rabbitbrush, huckleberry oak, pine and fir. Ornamental plants that should be removed or not planted in this area include evergreens (juniper, mugo pine, arborvitae, etc.), Scotch broom and large exotic grasses. When removing plants, leave their root systems in place.
• Noncombustible landscape materials, such as gravel, rock and brick, are acceptable.
• Use low-growing (less than 18 inches tall), irrigated, herbaceous plants, such as lawn, clover, erosion- control grasses, flowers, some ground covers and succulents, that are recommended for the Lake Tahoe Basin.
• Use low-growing (less than 18 inches tall), irrigated, deciduous shrubs recommended for the Lake Tahoe Basin as individual specimens or in small groups. Prune these shrubs to remove branches in contact with the ground and sides of the house.
• Do not plant shrubs under first-story windows, under soffit vents, in front of foundation vents, or in corners.
• Use trellises made of noncombustible materials.
Step 7: Maintain the Defensible Space Zone.
The last step to creating defensible space is maintenance. Maintaining a defensible space is an ongoing activity. Plants grow back and flammable vegetation needs to be routinely removed and disposed of properly. Before each fire season, reevaluate your property using the previous six steps and implement the necessary defensible space recommendations.
The defensible space zone needs to be maintained on a regular basis.
