General
Since 1980, California laws and codes have pursued mitigation strategies to reduce loss of life, property, and natural resources within a Fire Hazard Severity Zone (FHSZ).
Which projects are subject to WUI requirements?
The 2025 California Wildland-Urban Interface Code (CWUIC) sections 101.3.1 & 101.5, designate WUI building requirements apply to all new structures, additions, and exterior alterations (including accessory structures) located in a FHSZ designated:
- State Responsibility Area (SRA).
- Local Responsibility Area (LRA), High or Very High.
How to determine if a parcel is within an applicable FHSZ?
Verify the fire zone classification using the official California State Fire Marshal FHSZ Viewer. Enter the property address to identify the exact zone.
What are the WUI standards and local amendments?
- California Code: 2025 California Wildland-Urban Interface Code (CWUIC) and emergency supplement became effective January 1, 2026.
- 2025 CWUIC Amendments: SCCC 12.10.247 amendments delete section 101.3.1 exceptions 1, 2, and 4, and the corresponding sections of chapter 5.
What WUI documentation is required for submittal review?
Submittals must delineate specific compliance standards tailored to the proposed construction meeting current codes and amendments. The below is not all-inclusive and subject to change.
Documentation must include specific assembly details, material specifications, and copies of current OSFM BML Listing sheets or approved products of the 2025 OSFM WUI Listed Products Handbook. Failure to provide project-specific details and listings will delay plan approval and require plan check corrections.
- Material Approvals & Labeling: Must be approved/listed by the State Fire Marshal (OSFM). CWUIC 503
- Surface Treatments: Coatings or paints are not approved protection methods. CWUIC 503.2.5
- Roof Assembly: Class A rating required. CWUIC 504.2
- Roof Valleys: Flashing and Underlayment. CWUIC 504.2.2
- Eaves & Soffits: Exposed underside. CWUIC 504.3
- Gutters & Downspouts: Leaf/debris guards and noncombustible materials. CWUIC 504.4
- Exterior Walls: Assemblies and wall coverings. CWUIC 504.5
- Flashing (Walls): Vertical metal flashing or noncombustible material at ground, decking and roof intersections. CWUIC 504.5.1
- Underfloor Enclosure: Compliant construction. CWUIC 504.6
- Projections: Attached unenclosed accessory structures and projections. CWUIC 504.7
- Decks: Flashing and the walking surface material of decks, porches, balconies and stairs. CWUIC 504.7.3
- Glazing/Windows/Glazed Doors: Type and compliance standard. CWUIC 504.8
- Operable Skylights: Noncombustible mesh screen and opening size. CWUIC 504.8.2
- Exterior Doors: Type and compliance standard. CWUIC 504.9
- Garage Doors: Automatic opener battery backup and perimeter gap. CWUIC 504.9.1, 504.9.2
- Vents: Specify on the plans the products and submit the OSFM approved listing or WUI tested to ASTM E2886 listing. Ventilation openings for enclosed attics, gable ends, ridge ends, under eaves and cornices, enclosed eave soffit spaces, enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters, underfloor ventilation, foundations and crawl spaces, or any other opening intended to permit ventilation, either in a horizontal or vertical surface. CWUIC 504.10, 504.10.1
- Off Ridge and Ridge Vents: If a WUI listing is not provided, specify vents shall be covered with a mesh where the dimensions of the mesh therein shall be a minimum of 1/16 inch and shall not exceed 1/8 inch in diameter, noncombustible and corrosion resistant. Note: The vent product Net Free Ventilation Area (NFVA) may need to be adjusted for reduced mesh openings and calculations submitted for review. CWUIC 504.10.2
- Vent Locations: Gable-end and dormer vents shall be located not less than 10 feet from lot lines. Underfloor ventilation openings shall be located as close to grade as practical. CWUIC 504.10.3
- Accessory Buildings and Miscellaneous Structures: Per SCCC 12.10.247 scoping, CWUIC 504.11 is not applicable, all structures require WUI compliance.
- Replacement or Repair of Roof Coverings: The roof covering on buildings or structures in existence prior to the adoption of this code that are replaced or have 50 percent or more replaced in a 12-month period shall be replaced with a roof covering required for new construction in accordance with Sections 504.2 and 504.2.1. All portions of a roof covering applied during an addition, alteration or repair to an existing structure shall meet at least a Class A fire classification. CWUIC 507.1
- Spark Arrestors: Wire screening of 12 USA gage wire, openings 1/2-inch maximum and 3/8-inch minimum, net free area not less than four times the net free opening. CWUIC 605; CBC 2113.9.2, 2802.1; CRC R1003.9.2
- Liquefied Petroleum Gas Installations: Installed in accordance with the California Fire code. LP-gas storage tanks shall have a minimum clearance of 10 feet down to bare mineral soil in all directions. Vegetation more than 10 feet but less than 20 feet from an LP-gas storage tank shall be fire-smart vegetation. CWUIC 606; CFC 6104.3, 6107.3, 6107.4
Inspection and Certification
Final inspection and certification confirm compliance with all wildfire exposure standards, while vegetation clearance is managed by local fire agencies. CWUIC 101.4, 502