Wildfire Hazard Potential — what the USFS scale means and how to defend your home

The 5-step WHP scale

Very Low: minimal fuel continuity; suppression usually contains rapidly. Common in irrigated farmland.

Low: scattered fuels; suppression effective most of the year.

Moderate: continuous but interrupted fuels; large fires possible during drought + wind.

High: dense fuels with topographic alignment to wind; fast fires, high-spread-rate.

Very High: extreme conditions favor large catastrophic fires; firefighters often defensive only.

WHP changes with land use — wildland-urban interface (WUI) zones are where most US fire-loss happens.

Defensible space — the 0–5, 5–30, 30–100 rule

Zone 1 (0–5 ft from structure): non-combustible. No mulch, no plants directly against siding. Use rock, gravel, or concrete.

Zone 2 (5–30 ft): low/lean/spaced. Mowed grass, irrigated low shrubs, no continuous foliage that lets fire ladder up trees.

Zone 3 (30–100 ft): reduced fuel. Trees thinned to 10ft spacing crown-to-crown. Low limbs pruned to 6ft. No woodpiles or sheds.

These zones are explicitly required by California's WUI building code and recommended in most other Western states.

Hardening the structure

Roof: Class A fire-rated. Asphalt shingles (most common) qualify; cedar shakes do not.

Vents: 1/8-inch metal mesh on attic and crawl-space vents (not standard 1/4-inch — embers fit).

Eaves: enclosed soffits, not open. Embers love open eaves.

Windows: dual-pane tempered glass minimum. Single-pane shatters from radiant heat.

Decks: composite with no flammable material below. Embers collect under wood decks.

What zipradar shows

USFS Wildfire Hazard Potential at the community level for your ZIP, with the 5-step rating in plain English plus a link to mitigation resources.

For property-specific risk assessments, contact your county's CalFire or state-equivalent fire-protection district. Insurance underwriters increasingly use property-level overlays beyond the community WHP.