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What is Defensible Space?

Definition :

An area around your home or structures, which is either man-made or natural where the vegetation is modified and maintained to slow the rate and intensity of an advancing wildland fire. It also provides room for firefighters to work and helps protect the forest from becoming involved should a structure fire occur.

Severe wildfire hazards exist on most forested building sites. Many hazards can be effectively reduced by following these defensible space guidelines developed by the Colorado State Forest Service. Follow the guidelines below.

  • Thinning out continuous tree and brush cover around structures. The initial 15 feet around a structure should consist of an area which all flammable vegetation is removed. Beyond the initial 15 feet, the trees should be thinned to 10 - 12 foot crown spacing. Occasionally, clumps of 2 or 3 trees are permitted for natural effects if more space surrounds them. The dimensions of a defensible space are subjective, site specific and dependent on site characteristics.
  • Dispose of all slash and debris left from thinning by either chipping, hauling away or by piling and burning.
  • Remove dead limbs, leaves and other ground litter within the defensible space.
  • Stack firewood uphill or on a contour and at least 15 feet from your home.
  • Maintain an greenbelt immediately around your home using grass, flower gardens, or ornamental shrubbery. An alternative is rock or other noncombustible material; avoid bark or wood chip mulch in this area.
  • Mow dry grass and weeds to a height of 6 inches or less for a distance of 30 feet.
  • Prune branches from trees within the defensible space to a height of 10 feet above the ground fuels. Also remove shrubs and small trees, or other potential "ladder" fuels from beneath large trees; left in place, these can carry a ground fire into the tree crowns.
  • Trim branches which extend over eaves of roofs. Remove branches within 15 feet of a chimney.
  • Clean roof and gutters of pine needles and leaves to eliminate an ignition source for firebrands, especially during the hot, dry weather of the fire season.
  • Reduce density of surrounding forest at least 100 feet out from your structure. Thin the trees so there is 10 foot crown spacing.
  • Maintain the defensible space annually, by removing debris, shrubs and other vegetation which accumulated during the year.
Diagram of defensible space