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Lay out defensible space and fire breaks

Design zones of reduced fuel around every building so embers and flames are less likely to ignite them. Wildfire guidance commonly uses three zones out to 100 ft (about 30 m), but local rules may require more.

How

  1. Immediate zone, 0 to 5 ft: noncombustible surfaces such as gravel or pavers; no woodpiles, mulch or shrubs; no branches overhanging the roof.
  2. Intermediate zone, 5 to 30 ft: mown grass at 4 in or less, spaced trees with ladder fuels removed, tree branches at least 10 ft from the house and chimney.
  3. Extended zone, 30 to 100 ft (or to the property line): remove dead plants and litter, thin trees, and keep firewood here, with bare ground around exposed piles.
  4. Increase spacing on slopes. CAL FIRE guidance suggests shrub spacing of about 2 times shrub height on flat ground, 4 times on mild to moderate slopes and 6 times on steep slopes, and 10, 20 and 30 ft between trees respectively.
  5. Keep 10 ft of clear ground around LPG tanks and no flammable vegetation for a further 10 ft.
  6. Place outbuildings about 30 ft from the house, or treat them as part of the house in the fire plan.
  7. Use driveways, gravel paths, irrigated gardens and fire-resistant plantings as fuel breaks, and check your local fire service rules, which may be stricter (for example San Diego County uses 50 ft for the intermediate zone).
  8. Australia example: CSIRO calls this a defendable space (an Asset Protection Zone in some states). It is managed vegetation that cuts flame contact and radiant heat and gives firefighters room.
  9. Australia rates the house itself by Bushfire Attack Level under AS 3959. Build to the rating with design-28.

Safety: Use protective equipment and follow local burn and equipment-use restrictions when clearing vegetation in fire season.

Do these first

Sources

  1. Defensible Space. CAL FIRE (Ready for Wildfire), accessed 2026-11
  2. Defensible Space: Protection Against Wildfires. Pacific Northwest National Laboratory, Building America Solution Center (US DOE), accessed 2026-11
  3. Firewise Landscapes. University of Arizona Cooperative Extension, accessed 2026-11
  4. Siting defendable spaces (Bushfire best practice guide). CSIRO, Australia, accessed 2026-11
  5. Construction of buildings in bushfire-prone areas (AS 3959). Housing Industry Association, Australia, accessed 2026-11

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