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Fire and safety · Design out fire and fuel hazards · safety-4

Lay out wildfire defensible space zones

Defensible space is the managed area around buildings that slows a wildfire and stops embers igniting things next to the house. US guidance from NFPA Firewise and CAL FIRE uses three zones measured from the building; other countries have their own versions.

How

  1. Immediate or Zone 0 (0 to 5 ft, about 1.5 m): keep it noncombustible. Use gravel, pavers or concrete instead of wood mulch, remove dead plants, and move firewood, bins and vehicles out. Research cited by Texas A&M Forest Service says this zone has the greatest effect on risk. Pay extra attention to building corners.
  2. Intermediate or Zone 1 (5 to 30 ft, about 1.5 to 9 m): lean, clean and green. CAL FIRE examples: remove dead leaves and needles from yard, roof and gutters; keep 10 ft (3 m) between trees; trim branches 10 ft from chimneys; clear vegetation under decks.
  3. Extended or Zone 2 (30 to 100 ft, about 9 to 30 m, or to the boundary): reduce fuel. CAL FIRE examples: cut annual grass to 4 inches (10 cm) or less, space shrubs and trees, and keep wood piles with 10 ft of bare soil around them.
  4. Break ladder fuels. CAL FIRE suggests trimming branches at least 6 ft (1.8 m) above ground and keeping a vertical gap of three times the shrub height between shrub tops and the lowest tree branches.
  5. Increase spacing on slopes. CAL FIRE examples: 10 ft between trees on flat ground, 20 ft on mild to moderate slopes and 30 ft on steep slopes.
  6. Give outbuildings and LPG tanks 10 ft (3 m) of bare ground and no flammable plants in the next 10 ft, as CAL FIRE recommends.
  7. Check local rules. Some areas require more: one US guide notes San Diego County requires 50 ft in Zone 1. Work with neighbours where zones cross boundaries.
  8. Site choice comes first: see site-12 for wildfire risk when choosing land.

Safety: Use chainsaws and brush cutters only with training and protective gear, and never during high fire danger days when sparks can start fires.

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 Fact Sheet: Immediate Noncombustible Zone. Texas A&M Forest Service, accessed 2026-11

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