Learning Resources

Defensible space is the buffer of cleared and managed vegetation around a structure that slows the spread of fire and gives firefighters room to work. California law divides it into three zones based on distance from the structure — Zone 0 (0–5 ft), Zone 1 (5–30 ft), and Zone 2 (30–100 ft) — each with its own requirements.

See the full zone breakdown →

California's primary defensible space law is Public Resources Code § 4291, which requires homeowners in State Responsibility Areas to maintain 100 ft of clearance. In 2021, AB 3074 added the Zone 0 ember-resistant zone (0–5 ft) as a new requirement, phased in starting in 2023.

How Prefire scores compliance →

Fire spreads significantly faster uphill roughly doubling in speed for every 10° of slope. California regulations account for this by tightening horizontal tree-spacing requirements on steeper terrain. A tree that meets spacing rules on flat ground may be too close on a 30% slope.

How Prefire applies slope data →

Most homes ignite not from direct flame contact but from embers landing in vulnerable spots; wood shake roofs, open vents, and combustible siding are the biggest risks. Upgrading to Class A roofing, installing ember-resistant vent covers, and replacing wood siding with fiber cement or stucco are among the highest-impact changes a homeowner can make.

IBHS: Wildfire Ready Home Guide ↗ · Ready for Wildfire: Harden Your Home ↗

Having a plan before a fire starts is critical since wildfires can move faster than evacuation orders. Know your evacuation routes, have a go-bag ready, sign up for local emergency alerts, and establish a family meeting point outside the fire zone.

Ready.gov: Wildfire Preparedness ↗ · Ready for Wildfire: Go! Evacuation Guide ↗

The Prefire analyzer lets you draw your property on a satellite map, answer a short questionnaire about site conditions, and receive a personalized defensible space compliance estimate. No account required and it's free to use.

Try the analyzer → · How it works →