FHSZ Construction Requirements

Wildland Urban Interface (WUI) building requirements in California (Part 7) apply to new construction, remodels, and additions in designated high-fire risk areas, including Very High, High, and Moderate FHSZs. 

No. For construction repairs, alterations, additions, and new construction, all requirements of the Wildland Urban Interface (WUI) code are the same for all FHSZs.

  • Roof:
    • Class A roof covering, with fire‑resistant valleys, and noncombustible or protected gutters.
  • Exterior walls:
    • Noncombustible or ignition‑resistant siding and wall assemblies, with limited flame spread, and protection at joints and penetrations.
  • Vents and openings:
    • Ember‑ and flame‑resistant vents (or 1/16–1/8‑inch corrosion‑resistant metal mesh), with locations and designs intended to resist ember intrusion at eaves, attics, crawlspaces, and under‑floor areas.
  • Windows and doors:
    • Tempered or otherwise fire‑resistant glazing, limits on vinyl frame use unless tested, and solid or rated exterior doors to reduce breakage/ignition from radiant heat and embers.
  • Eaves, soffits, projections:
    • Enclosed or boxed‑in eaves with noncombustible/ignition‑resistant materials; unprotected open eaves are generally not allowed in WUI.
  • Decks and attached structures:
    • Decking within a set distance (typically 10 feet) of buildings must be noncombustible or ignition‑resistant per State Fire Marshal 12‑7A testing; similar concepts apply to attached stairs, landings, and balconies.
  • Accessory structures and fences:
    • Certain accessory buildings and combustible fences within close proximity to structures are limited or must be noncombustible/ignition‑resistant near the home.

The State Fire Marshal has created an approved list. If you are unsure, please give us a call at (650) 616-7074.