Defensible space basics: Zones 0, 1, and 2

California law (Public Resources Code 4291) requires homeowners in fire-prone State Responsibility Areas to maintain defensible space in concentric zones around the home. Since 2020 (AB 3074) the rule explicitly includes Zone 0 — the noncombustible 5-foot ember zone — in addition to the older 100-foot defensible-space requirement.

Zone 0 (0–5 ft): the ember-resistant zone. Noncombustible only. No bark mulch, no shrubs against siding, no wood fence touching the house, no stored firewood. See our Zone 0 guide for details.

Zone 1 (5–30 ft): the lean, clean, and green zone. Remove dead plants and litter, prune trees, keep shrubs spaced, and irrigate what remains so it stays green through fire season.

Zone 2 (30–100 ft): the reduced-fuel zone. Thin trees and shrubs to break the fuel ladder from grass to canopy. Remove ladder fuels under tree crowns and keep grass cut below 4 inches.

Defensible space sounds like it's about creating a clear zone where flames can't reach the house. That helps, but it's not the main mechanism. Post-fire investigations consistently find that 60–90% of homes destroyed in a wildfire ignite from embers — small wind-blown pieces of burning material that travel up to a mile ahead of the fire front.

Embers land in gutters full of dry leaves, blow into open attic vents, drift through screened windows, and pile up against combustible siding. Defensible space is really ember-defensible space: the goal is to deny embers the fuel they need to start a fire that spreads to the structure.

This is why a perfectly maintained Zone 2 with a flammable Zone 0 is a house that loses. Embers don't care about your hundred-foot setback if there's a bark bed under your living-room window.

Remove all dead and dying vegetation — branches, brown lawn, leaf litter, dead annuals. Dead material is the fastest-igniting fuel in your yard.

Space shrubs so that crowns are at least 2× the shrub height apart on flat ground, more on slopes. A continuous shrub bed is a continuous fuel path.

Prune the lower branches of trees up to 6–10 feet (or 1/3 of total tree height, whichever is less). This breaks the ladder fuel — the chain that lets a ground fire climb into a tree crown.

Keep grass under 4 inches and irrigated if possible. Dry annual grass is the most ignitable fuel in California; one ember in 6-inch summer grass is a fire.

Remove anything stored against the house or under decks: lumber, plywood, patio cushions, garbage cans, and especially firewood. Firewood belongs at least 30 feet from any structure.

Thin trees so that canopies are at least 10 feet apart on flat ground, more on slopes. Continuous canopy carries crown fires straight across a property.

Remove ladder fuels: small trees, shrubs, and limbs under larger tree crowns that would let a ground fire climb up.

Mow or graze annual grasses to under 4 inches by early summer. A green pasture is good defensible space; the same pasture in August is fuel.

Keep the area free of stacked slash, old building materials, and rusting vehicles full of dry seat foam.

Zone 2 management is often the biggest physical job on the property — chainsaw work, chipping, hauling. Many counties run free chipping programs in spring; check your local Fire Safe Council.

Start at Zone 0 and work outward. A perfectly maintained Zone 2 with a flammable Zone 0 is a house that loses to embers.

Then clean the roof and gutters of all needles, leaves, and debris. This is one of the highest-impact, lowest-cost fixes anywhere on a property.

Then look at your vents (see our ember-resistant vents guide). After that, move outward into Zone 1 spacing and pruning, then Zone 2 thinning.

Treat defensible space as annual maintenance, not a one-time project. The Zone 1 you cleared in March will have a new layer of needles and dropped branches by August.

Treating it as a one-time check-the-box. Vegetation grows back. Annual grasses cure. Storm debris accumulates. Defensible space is a yearly maintenance commitment.

Cutting down every tree. You don't need a moonscape. Healthy, well-spaced, properly pruned trees actually slow fire and trap embers. The enemy is continuous fuel, not trees themselves.

Ignoring the neighbor's yard. Embers and radiant heat from a neighbor's unmaintained lot can defeat a perfect Zone 1 on yours. If you can, talk to neighbors — many fire-safe councils mediate these conversations.

Forgetting the propane tank, transformer pad, and detached structures. Defensible space rules apply to outbuildings, sheds, and ADUs too.