Given the wildfire seasons of the last few years, defensible space is a term you may have heard in the news. Defensible space is an area around your home with reduced vegetation levels, and is used to give firefighters a safe space to defend your home. In conjunction with home hardening, defensible space will give your home a much better chance surviving a fire, even if fire fighters are not able to actively defend the structure.

In neighborhoods where houses are closer than 30 feet (for example the Berkeley and Oakland hills), home hardening becomes more important, as the radiant energy from a burning building can be enough to ignite an adjacent structure, even with little or no vegetation in between.

Fire Severity Zones
Defensible space is most critical in areas prone to wildfires, known as High Fire Severity Zones. It makes sense that forested areas are prone to wildfire, but any area with dense, dry vegetation can be vulnerable. For example, the Coffey Park area of Santa Rosa, which is a fairly typical, flat, suburban neighborhood, was leveled by the 2017 Tubbs Fire.

Coffey Park, Santa Rosa – before and after the 2017 Tubbs Fire

California law (Government Code 51182) requires property owners to maintain defensible space around structures located in very high fire severity zones. California law (Public Resource Code 4291) requires all owners with land covered in flammable material, to maintain defensible space. California law (Civil Code 1102.19) requires property sellers in high or very high fire severity zones to provide documentation stating that the property is in compliance with defensible space regulations.

Defensible Space Zones 
The defensible space around your home is divided into three distinct zones, from zone zero (closest to the home) to zone two (farthest from the home)

Zone 0 – Ember-Resistant Zone – extends 0 – 5 feet from buildings, structures, decks, etc.

  • For walkways, use materials like gravel, pavers, or concrete – not combustible bark or mulch
  • Replace combustible fencing, gates, and arbors attached to the home with noncombustible (e.g. metal) alternatives
  • Relocate outdoor furniture, planters, etc to Zone 1
  • Relocate firewood and lumber to Zone 2
  • Limit plants in this area to low growing, non-woody, properly watered and maintained plants
  • Remove all dead and dying vegetation and debris (leaves, needles, cones, bark, etc.)
  • Relocate garbage & recycling containers, boats, RVs, etc. to Zone 1 or Zone 2

Zone 1 – Lean, Clean, & Green Zone – extends 5 – 30 feet from buildings, structures, decks, etc.

  • Choose only fire resistant plants, and keep them healthy and well irrigated
  • Trim trees regularly to keep branches a minimum of 10 feet from other trees
  • Remove tree limbs that are 6-10 feet from the ground
  • Provide spacing between shrubs, at least 2 times the height of the mature plant (Add space on steeper slopes)
  • Remove fire-prone plants and dead vegetation
  • Remove vegetation and flammable items from around and under decks, awnings, balconies, and stairs
  • Relocate firewood and lumber to Zone 2
  • Outbuildings and LPG storage tanks should have at least 10 feet of clearance

Zone 2 – Reduced Fuel Zone – extends 30 – 100 feet from buildings, structures, decks, etc.

  • Create vertical space between grass, shrubs and trees (See diagram below)
  • Create horizontal space between shrubs and trees (See diagrams below)
  • Cut or mow annual grass down to a maximum height of 4 inches
  • Fallen leaves, needles, twigs, bark, cones, and small branches are permitted to a depth of 3 inches
  • All exposed wood piles must have a minimum of 10 feet of clearance, down to bare mineral soil, in all directions

Zone 2 – Vertical Spacing

Zone 2 – Horizontal Spacing

Diagrams courtesy of CalFire. More information:

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