Defensible Space

Defensible Space and Fire Safe Landscaping in San Mateo CountySan Mateo county hillsides, while beautiful, are an ideal environment for a devastating wildland fire.  With the onset of summer months comes the drying and curing of our lands.  As temperatures peak, humidity drops, and the summer winds blow, the potential for wildland fires increases.  Despite the efforts of the fire services, many homes are lost each year due to wildland and wildland-urban interface fires.  It is imperative that you prepare now to protect your home from such occurrences.

Defensible space is essential to improve your home’s chance of surviving a wildfire. It’s the buffer you create between a building on your property and the grass, trees, shrubs, or any wildland area that surround it. This space is needed to slow or stop the spread of wildfire and it protects your home from catching fire – either from direct flame contact or radiant heat. Defensible space is also important for the protection of the firefighters defending your home. 

More than 1,445 structures are destroyed by wildfire each year just within the jurisdiction of California’s Department of Forestry and Fire Protection (CAL FIRE).  However, many homes are also saved as a result of the owners’ careful pruning and landscaping techniques that minimize ignition of vegetation and spread of fire to their homes (CAL FIRE 2005).

Incorporating fire-safe concepts into the residential landscape is one of the most important ways you can help your home survive a wildfire. When conditions are dry and windy, the grasses, brush, trees, or other vegetation surrounding your home become a dangerous fuel source. Creating an area of defensible space (or area of reduced fuel) between your home and flammable vegetation reduces the risk of home ignition. When the vegetation is removed, pruned, or otherwise modified, the chance that its ignition will pose a serious threat to your home during a wildfire diminishes.

Your home may be the most valuable investment you ever make. If you live in a high-risk fire hazard area, protect against the chance of losing that investment by creating defensible space and using fire-resistant construction materials and techniques.  Creating an area of defensible space does not mean you need a ring of bare dirt around your home. Through proper planning, you can have both a beautiful landscape and a fire-safe home. The general concept is that trees should be kept furthest from your house, shrubs can be closer, and bedding plants and lawns may be nearest the house.

Defensible Space Zones

Two zones make up the required 100 feet of defensible space.  The two zones are the home defense zone; and the reduced fuel zone (see "Defensible Space Zones, below).  The home defense zone is within 30 feet of the house. The reduced fuel zone lies beyond the home defense zone and extends out at least 100 feet from the house or to your property line.  Greater defense zone widths are necessary when your home is on a steep slope or in a windswept exposure.  Specific recommendations for each zone are described below and pertain to the State Responsibility Area (SRA) protected by CAL FIRE. Local Responsibility Areas that are protected by citly or county fire departments may have slightly different requirements.


Zone 1

Zone 1 extends 30 feet* out from buildings, structures, decks, etc.

  • Remove all dead plants, grass, and weeds (vegetation).
  • Remove dead or dry leaves and pine needles from your yard, roof, and rain gutters.
  • Trim trees regularly to keep branches a minimum of 10 feet from other trees.
  • Remove branches that hang over your roof and keep dead branches 10 feet away from your chimney.
  • Relocate wood piles into Zone 2.
  • Remove or prune flammable plants and shrubs near windows.
  • Remove vegetation and items that could catch fire from around and under decks.
  • Create a separation between trees, shrubs, and items that could catch fire, such as patio furniture, wood piles, swing sets, etc.

Zone 2

  • Cut or mow annual grass down to a maximum height of 4 inches.
  • Create horizontal spacing between shrubs and trees. (See diagram)
  • Create vertical spacing between grass, shrubs and trees. (See diagram)
  • Remove fallen leaves, needles, twigs, bark, cones, and small branches. However, they may be permitted to a depth of 3 inches if erosion control is an issue.

* San Diego County requires 50 feet of clearance in zone 1. Check with your local fire department for any additional defensible space or weed abatement ordinances. 


Fire Safe Landscaping

Defensible Space requires the installation and maintenance of Fire Safe Landscaping.  It is important to remember that a fire-safe landscape isn't necessarily the same thing as a well-maintained yard.   A fire-safe landscape uses fire-resistant plants that are strategically planted to resist the spread of fire to your home.  

The good news is, you don't need a lot of money to make your landscape fire safe. And you will find that a fire-safe landscape can increase your property value and conserve water while beautifying your home.

Learn more about Fire Safe Landscaping practices and materials here...


Hardening Structures Against Wildfire

During a wildfire, tiny burning embers can fly far ahead of the fire, sometimes igniting homes a mile or more away from the fire itself.  A wildfire-safe home must be resistant to ignition from these flying embers so that even if the flames do not reach your home, it will be able to withstand exposure to embers that may have been blown a mile or more in front of a wildfire.  To provide maximum wildfire protection for your home, a combination of near-home vegetation management, appropriate building materials, and related design features must be used.

Learn more about fire-resistant construction practices and materials here...


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The information contained on this page is derived from several print and online sources:

  • University of California Publication 8228.  Home Landscaping for Fire.  2007.  University of California, Davis.
  • Wildfire is Coming: Are You Ready.  CAL FIRE.  2012.  
  • Urban Forestry Associates.  Ray Moritz, Urban Forester and Fire Ecologist.  

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