Creating a defensible space

FireWise Minnesota

Creating a defensible space around your house can enable it to survive a wildfire. This space is between your home and the untouched wildland. Creating a defensible space minimizes the likelihood of flames or surface fire touching the home or any attachments, such as a garage or deck.

See the difference between being unsafe and being Firewise in the photos below. Can you spot the changes?

showing a house with tree close to the house.


showing the same house with tree further away from house.


Creating a defensible space

Step 1

  • Use the Do-it-yourself Home Risk Assessment Guide. You can also request a Firewise homeowner's kit to receive a copy of the guide and brochures mailed to you.
  • Assess your property:
    • Do you border wildland?
    • Is there a substantial amount of tall vegetation crowded around your home?
    • Do tree limbs extend over your home?
    • Do you have a woodpile near your home?
    • Do you have any fuel tanks nearby?
    • Have you used native vegetation in your landscaping?
    • Does your property's driveway provide access to your home for firefighters?

Step 2

Start by dividing up your property into three zones: Immediate (0-5 feet), Intermediate (5-30 feet), and Extended (30-100 feet).

Immediate zone

The first is the immediate zone - within 5 feet of the structure. The home will likely be lost if a wildfire is allowed to reach this zone. Fire can reach this zone by traveling on the ground through flammable materials such as tall grass, wooden walkways, and fences or by flying embers from a nearby fire that catches fire in materials within this zone.

Intermediate zone

The next zone includes everything from 5 to 30 feet of the structure. Any decks or outbuildings inside this zone are considered part of the structure and extend the zone 30 feet beyond them. If properly landscaped, this zone can prevent a wildfire from reaching the structure zone.

Extended zone

The third zone is the extended zone. It extends 100 feet beyond structures and is generally where the woods or other wild areas are. This area is where excess fuel, such as downed trees, heavy brush, and dense conifer plantations, should be reduced.

Step 3

Consider your home assessment and what wildfire risk reduction projects you want to focus on. In 50 things you can do to protect your home you'll find additional examples of projects, including home construction materials and visibility, broken down by cost.

Immediate zone project examples
  • Limit plantings, especially evergreen shrubs, 3 to 5 feet of the structure, particularly if the building is sided with wood, logs, or other flammable materials. Decorative rock creates an attractive, easily maintained, nonflammable ground cover.
  • If the house has noncombustible siding, widely spaced foundation plantings of low growing shrubs or other "fire resistant" plants are fine. Do not plant directly beneath windows or next to foundation vents. Be sure there are no areas of continuous grass adjacent to plantings in this area.
  • More firewood and other combustible materials out of the immediate zone.
  • Extend the gravel coverage under the decks. Decks within 5 feet of the ground should be enclosed with metal screening or sheeting.
  • Frequently prune and maintain plants. Remove dead branches, stems and leaves.
  • Keep grass mowed short (1–2").
  • Ideally, remove all conifer trees from the Intensive Zone to reduce fire hazards. If you do keep a few conifer trees, be sure they are well spaced with at least 10 feet between their crowns and that they are pruned up at least 8 feet.
  • Remove any branches that are within 10 feet of the roof or chimney.
  • Remove all "ladder fuels" from beneath the tree. (Ladder fuels are tall grass, small shrubs, trees, tree limbs and other materials that allow fire to climb into the tree crown.)
  • Propane tanks pose a special hazard near homes. Tanks up to 1200 gallons are best located inside the defensible space but must be at least 10 feet from the structure itself. In addition, grass and bushes must be cleared around the tank for 10 feet. Contact your local fire marshal before moving an existing tank.
Intermediate zone project examples
  • Thin trees and large shrubs so there are at least 10 feet between crowns. Crown separation is measured from the outer most branch of one tree to the closest branch on the next tree.
  • Because this zone forms an aesthetic buffer and provides a transition between zones, it is necessary to blend the requirements from the other two zones. Thin the inner portions more heavily than the outer portions. Gradually increase tree density as you approach the extended zone.
  • Isolated shrubs may remain, provided they are not under tree crowns. Prune and maintain these plants periodically to maintain vigorous growth. Remove dead stems from trees and shrubs annually.
  • Limit the number of dead trees, or snags retained in this area. Wildlife need only one or two snags per acre. Be sure any snags left for wildlife cannot fall onto the house or block access roads or driveways.
  • Mow grasses to a maximum of 6 to 8 inches. This is extremely critical in the fall when grasses dry out and cure or in the spring after the snow is gone but before the plants green up.
  • Stack firewood and woodpiles at least 25 feet away. Remove flammable vegetation within 10 feet of these woodpiles. Do not stack wood against your house or on or under your deck, even in winter. Many homes have burned from an easily ignited woodpile next to the home!
  • Dispose of slash, (limbs, branches, etc.) from your trees and shrubs by chipping or composting. Some communities have brush disposal sites. Avoid burning this material. Another alternative is to lop and scatter slash by cutting it into very small pieces and distributing it over the ground to speed decomposition. Avoid heavy accumulations of slash. Make it lay close to the ground to speed decomposition. If desired, no more than two or three small, widely spaced brush piles may be left for wildlife purposes. Locate these towards the outer portions of your defensible space away from trees, especially evergreens, where they would create a fuel ladder.
Extended zone examples
  • Thinning trees can improve the forest stand. Remove trees that are damaged, attacked by insects, infected by disease, or are of poor form or low vigor.
  • A greater number of dead trees can remain in this zone. Make sure that they pose no threat to power lines or fire access roads.
  • While pruning generally is not necessary here, it may be a good idea from the standpoint of personal safety to prune trees along trails and fire access roads. If you prefer the aesthetics of a well-manicured forest, you might prune the entire area. In any case, pruning helps reduce ladder fuels within the tree stand, and enhances wildfire safety.
  • Mowing is not necessary here.
  • Any method of slash treatment is acceptable for this zone, including composting, piling, and burning, chipping or lop-and-scatter. Burning is discouraged since it is a major cause of wildfires. If you do plan to burn check the fire danger and burning restrictions map and get a permit if required.
Driveway examples

Projects around your driveways help firefighters can access your property.

  • Width of driveway: The all-weather should be at least 12 ft. wide, 20 feet if longer than 150 feet.
  • Vertical clearance: Engines and their equipment are tall. Prune tree branches to provide at least 14 ft. of clearance.
  • Turnaround: A turnaround near your house should be provided with at least a 30 ft. radius. A "Hammerhead - T" with a minimum of 60 ft. across the top, is a good alternative.
  • Turnouts: A turnout is a wide place in your driveway that will allow another vehicle to pass. It should be at least 10 ft. wide and 30 ft. long. If your driveway is over 800 ft. long, a turnout should be provided at least every 400 ft.

Step 4

Maintain your defensible spaces to keep the benefits of the Firewise protection.

  • Keep grass mowed to less than a 6-inch height and keep well-watered.
  • Remove litter and dead vegetation from foundation plants and mulch.
  • Prune dead branches and thin trees as their crowns begin to touch.
  • Remove annuals after they have gone to seed, or when the stems dry out.
  • Prune off the lower six to ten feet of branches from trees, but no more than a third of the tree's height.
  • Remove flammable materials around buildings such as firewood piles and lumber piles.

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