Defensible Space - For the Wildland Urban Interface

 

The most important goal for the improvement of life safety and property preservation is for every home to have conforming defensible space. Defendable space will do more to limit fire related property damage than any other single recommendation in the report.

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Zone 1 encircles the structure and all its attachments (wooden decks, fences, and boardwalks) for at least 30 feet on all sides. Note: the 30-foot number comes from the very minimum distance, on flat ground, that a wood wall can be separated from the radiant heat of large flames without igniting. In this area:

  • Plants should be carefully spaced, low-growing and free of resins, oils and waxes that burn easily.
  • Mow the lawn regularly. Prune trees up six to ten feet from the ground.
  • Space conifer trees 30 feet between crowns. Trim back trees that overhang the house.
  • Create a ‘fire-free’ area within five feet of the home, using non-flammable landscaping materials and/or high-moisture-content annuals and perennials.
  • Remove dead vegetation from under deck and within 10 feet of house.
  • Consider fire-resistant material for patio furniture, swing sets, etc.
  • Remove firewood stacks and propane tanks; they should not be located in this zone.
  • Water plants, trees and mulch regularly.
  • Consider xeriscaping if you are affected by water-use restrictions.

 

Zone 2 is 30 to 100 feet from the home, and plants in this zone should be low-growing, well irrigated and less flammable. In this area:

  • Leave 30 feet between clusters of two to three trees, or 20 feet between individual trees.
  • Encourage a mixture of deciduous and coniferous trees.
  • Create ‘fuel breaks’, like driveways, gravel walkways and lawns.
  • Prune trees up six to ten feet from the ground. 

 

Zone 3 is 100 to 200 feet from the home and this area should be thinned, although less space is required than in Zone 2. NOTE: Because of other factors such as topography, the recommended distances to mitigate for radiant heat exposure actually extend between 100 to 200 feet from the home – on a site-specific basis. In this area:

  • Remove smaller conifers that are growing between taller trees. Remove heavy accumulation of woody debris.
  • Reduce the density of tall trees so canopies are not touching ( at least 10- 15 feet)