Preparing a defensible space plan

6 Preparing a defensible space plan

Reduced Fuel Zone.
Image courtesy of and
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1. Begin by establishing the required 100-foot outer zone. With a fire awareness checklist in hand, start from your home and work outward. The assessment should identify fire risks to both your home and property.

Dangerous ladder fuel buildup.
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In the zone reaching out 100 feet (Reduced Fuel Zone), large tree plantings can be made, using non-pyrophytic or low fire ignition species. Shrubs should not constitute continuous fuel beds. The separation distance charts are helpful in determining wise plant spacing and future maintenance requirements. The separation guidelines are useful, as well, in keeping an eye on the development of ladder fuels.

Ladder fuels act to spread the flames upward.
Image courtesy of and
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The 100-foot outer zone is based on your structure being located on level land. Significant slope variations and fuel types may require extending the zone(s). If you are in doubt reference the following charts or contact your local Fire Marshal’s office. 

A daunting prospect
of vegetation removal.
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2. Once you have completed the assessment, you will have a better idea of the scope of your project, and you can prioritize your next steps. Don’t be overly concerned if the size of the project seems daunting. The goal is to take this one step at a time.

Dead and dying vegetation.
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3. Your priorities should focus on making the most impact with the least amount of effort. Removing dead and dying vegetation (including dry leaves, pine needles, limbs and small branches, brush parts, dead materials on the ground, unused timber, and debris piles) is first in all zones, starting closest to the house.

Dry, dead material that is ½ inch to 3 inches in diameter provides for high heat and is much easier to ignite than green materials.

Ladder fuels tend to spread fir upward into the crown.
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4. You will also want to break up the continuity of fire fuels by removal and spacing.

5. Ladder fuels, or fuels that tend to help a ground fire spread from ground level into the upper reaches of trees and brush, need to be removed.

6. Mow grasses for at least 50 feet around your structure each year, and maintain at a height of less than 3 inches throughout fire season.

An ideal open forest setting.
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7. Maintain an ongoing vegetation management program. Removing a source of fire fuel one year may not keep it from returning with a vengeance the following year. Plants grow and many resprout. Reference our plant list to help with removal techniques and timing.

Broom and many brush
species requires
ongoing maintenance.
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Here is an example of French Broom that returned after only two years.

In developing your new fire-safe landscape plan, only low-growing, irrigated plants should be planted within 10 feet of structures (Structure Ignition Zone). Check here for a list of recommended plants.



Napa Firewise

  To empower the citizens of Napa County with the information, knowledge, and support they need to survive a wildfire.