Wildfire Grant Finder

Wildfire Home-Hardening Glossary

Plain-English definitions of key terms used in wildfire mitigation, insurance, and home hardening. No jargon, just clear explanations.

Defensible Space

The area around your home where vegetation and combustibles are cleared or thinned to slow wildfire spread and reduce ember danger.

Defensible space is organized into three zones (0–5 feet, 5–30 feet, 30–100 feet) around your home. The closer you are to the house, the more aggressively cleared the zone should be. Zone 0 (closest) is completely noncombustible. Zone 1 has thinned trees and removed underbrush. Zone 2 is selective thinning further out. A well-maintained defensible space significantly reduces wildfire damage risk.

Also called "fuel reduction zone" or "shaded fuel break."

Zone 0 (Ember-Resistant Zone)

The 0–5 foot band directly around your home's foundation where everything must be noncombustible—no plants, wood, or mulch allowed.

Zone 0 is the most critical defensible-space zone because flying embers from distant wildfires can land here and ignite combustible materials. Use gravel, river rock, hardscape, or pavers only. Remove firewood piles, propane tanks, trash bins, and bark mulch. Use noncombustible fence sections where fences meet the house. This zone must be completely clear of fuel.

Also called "immediate home zone" or "home protection zone."

Home Hardening

Structural and exterior upgrades that make your home more resistant to wildfire embers, heat, and flame.

Home hardening includes: replacing roofs with Class-A materials, installing ember-resistant vents, enclosing eaves, upgrading to dual-pane windows, installing noncombustible siding, and creating defensible space. The goal is to eliminate ignition points where flying embers or radiant heat can start fires. A fully hardened home is significantly less likely to burn in a wildfire compared to an unmodified home.

Also called "wildfire mitigation," "fire-resistant construction," or "defensible space upgrades" (when focused on landscaping).

Class-A Roof

A roof rated to resist flame spread and ember penetration, the highest fire-resistance rating for roofing materials.

Class-A roofs are tested to ASTM E84 or UL 790 standards and include materials like architectural asphalt shingles, metal roofing, clay tile, slate, and composite shingles. They resist flame spread much better than lower-rated materials (like wood shakes). In wildfire zones, a Class-A roof is often the single most important structural upgrade because roofs are the primary point of ember ignition.

Lower ratings exist: Class B and Class C resist flame less effectively. Wood shakes are not fire-rated and should not be used in wildfire zones.

Ember-Resistant Vent

A roof or foundation vent with 1/16–1/8 inch noncombustible metal mesh that blocks flying embers while allowing airflow.

Standard vents have large openings where flying embers can lodge and ignite interior framing. Ember-resistant vents use fine metal mesh to filter out embers. They maintain ventilation for your attic or foundation while providing fire protection. These are one of the highest-impact, most cost-effective home-hardening upgrades.

Also called "1/16-inch mesh vent" or "wildfire-resistant vent." Look for vents rated by Firewise USA or certified to meet ASTM or UL standards.

WUI (Wildland-Urban Interface)

The area where homes and human development meet or are interspersed with wildland vegetation (forest, brush, grassland).

The WUI is where wildfire risk is highest because homes are adjacent to natural fuels that can burn. Homes in the WUI are exposed to ember storms, radiant heat, and direct flame. Most wildfire-prone US communities are in or near the WUI. Building codes in WUI areas often mandate defensible space or Class-A roofs.

Also called "wildland-urban interface zone" or "fire threat zone."

Fire Hazard Severity Zone (FHSZ)

A state or local designation that categorizes an area's wildfire risk based on vegetation, topography, climate, and weather patterns.

Most states classify areas as "High," "Moderate," "Low," or "Very High" fire hazard. California uses "Local Responsibility Area" (LRA) and "State Responsibility Area" (SRA) designations with severity zones. Your FHSZ affects building codes, insurance requirements, and eligibility for mitigation programs. Properties in high-hazard zones face stricter construction requirements and higher insurance rates.

Also called "fire threat zone," "wildfire hazard zone," or "fire risk zone." Check your local county assessor or state forestry website to find your zone.

Firewise USA

A nationwide program by the NFPA that recognizes communities committed to wildfire risk reduction through defensible-space and home-hardening standards.

Firewise USA provides resources, certification, community recognition, and group discounts on materials. Participating in Firewise (as an individual or community) can unlock insurance discounts, grant access, and collective purchasing power. Firewise standards align with best practices from NFPA and IBHS. Joining or forming a Firewise community is often the first step for homeowners seeking mitigation support.

Visit firewise.org to learn about programs in your area or to start a community program.

FAIR Plan

A state-run insurer of last resort that provides fire (and sometimes wildfire) insurance to homeowners who cannot obtain commercial coverage.

FAIR Plans exist in most high-fire-risk states. They offer insurance at standardized rates (usually higher than commercial policies) to homeowners denied or non-renewed by commercial insurers. California's FAIR Plan offers a discount (up to ~13.8%) for documented home hardening. If you're denied by commercial insurers, a FAIR Plan may be your only option for property insurance. Most FAIR Plans offer higher deductibles and more limited coverage than commercial policies.

FAIR = "Fair Access to Insurance Requirements." Each state's FAIR Plan operates independently. Check your state's insurance commissioner website for details.

PRC 4291

California Public Resources Code Section 4291, the state's primary law requiring defensible-space maintenance around homes in fire-prone areas.

PRC 4291 mandates that property owners maintain defensible space (Zone 0 and portions of Zone 1) to reduce wildfire risk. Local fire departments enforce the code through inspections, and violations can result in fines. Compliance typically requires: clearing dead vegetation, removing tree branches 6–10 feet up, maintaining 10-foot spacing between tree canopies, and clearing Zone 0 of combustibles. Other states have similar but differently-named defensible-space requirements.

Applies to properties in state responsibility areas (SRA) and local responsibility areas (LRA) in California. Check with your county fire department for specific requirements in your area.

Mitigation

Actions taken to reduce wildfire risk—either the risk of a fire occurring or the damage a fire causes to your home and property.

In the wildfire context, mitigation includes home hardening (structural upgrades) and defensible-space work (landscaping and clearing). Mitigation does not eliminate wildfire risk, but it significantly reduces damage. A mitigated home is much more likely to survive a wildfire. Mitigation is also used more broadly to mean any action that reduces disaster impact (e.g., flood mitigation, earthquake mitigation).

Also called "wildfire mitigation," "fire mitigation," or "hazard mitigation." In insurance and grant contexts, mitigation often refers to documented improvements eligible for discounts or funding.

Quick Reference

Key Terms by Category

Structural Upgrades

  • • Class-A Roof
  • • Ember-Resistant Vent
  • • Home Hardening

Defensible Space

  • • Defensible Space
  • • Zone 0 (Ember-Resistant Zone)
  • • PRC 4291 (CA regulation)

Risk & Location

  • • WUI (Wildland-Urban Interface)
  • • Fire Hazard Severity Zone (FHSZ)
  • • Mitigation

Programs & Resources

  • • Firewise USA
  • • FAIR Plan