California Wildland-Urban Interface Code (CWUIC)

The California Wildland-Urban Interface Code (CWUIC) is Part 7 of the California Building Standards Code (Title 24, California Code of Regulations). It sets ignition-resistant and fire-resistant construction requirements for new buildings located in the wildland-urban interface (WUI) — areas where development meets or intermingles with wildland fuels and is exposed to wind-driven embers, radiant heat and direct flame contact during a wildfire. The CWUIC is modeled on the International Wildland-Urban Interface Code (IWUIC) with California-specific amendments.

The 2025 CWUIC is a brand-new Part 7, effective January 1, 2026. For the first time, California consolidated its scattered wildfire-construction rules — formerly CBC Chapter 7A, California Residential Code Section R337 and California Fire Code Chapter 49 — into one standalone code. Because applicability depends on Fire Hazard Severity Zone (FHSZ) maps and local jurisdictions may adopt amendments, the exact requirements for your parcel depend on its mapped zone and your city or county — which is exactly what GoCodebook reconciles for you.

Because Part 7 is new, the practical problem for most teams is re-mapping citations. A detail that used to cite "CBC 704A.3" or "R337.7" now has a Part 7 section number, and plan checkers in different jurisdictions may still be working from the older references during the transition. The section list below opens the adopted Part 7 text so you can cite the current source.

The CWUIC focuses on hardening a building against ember intrusion, radiant heat and direct flame — the three ways wildfires ignite structures. Core requirements include Class A roof assemblies, ember-resistant vents (typically with 1/16-inch to 1/8-inch noncombustible mesh), ignition-resistant or noncombustible exterior walls and siding, tempered or multi-pane exterior glazing, and ignition-resistant decking, eaves, soffits and overhangs. The exterior material standards that used to sit in CBC Chapter 7A now live in the CWUIC, including the SFM-listed product and ASTM test requirements builders cite during plan check.

The code applies to new buildings, additions and certain reconstruction in a designated WUI fire area or Fire Hazard Severity Zone. Whether a parcel is in a moderate, high or very high fire hazard severity zone (VHFHSZ) drives how strict the construction requirements are. The CWUIC governs the structure itself; defensible space vegetation clearance (the 100-foot Zone 0/1/2 rules) is handled separately under state fire law and the California Fire Code. See where coverage is deepest.

Applicability is map-driven. California publishes Fire Hazard Severity Zone maps for both State Responsibility Areas (SRA) and Local Responsibility Areas (LRA), and CAL FIRE updated these maps in 2024–2025, expanding the acreage classified as high or very high hazard. If your parcel falls in a mapped zone — or a locally designated WUI fire area — the CWUIC construction standards apply to new work even when the surrounding neighborhood predates the rules.

Many people confuse the building code (CWUIC, Part 7) with vegetation and defensible-space requirements, but they are distinct. The CWUIC is enforced at plan check and permit for the structure, while defensible space is inspected in the field. Existing homes are generally not required to retrofit unless they undergo significant alteration — though insurers increasingly request WUI-hardening upgrades. For change-of-occupancy and major alteration questions, the California Existing Building Code also comes into play.

A WUI project rarely triggers Part 7 alone. The base structure is still designed under the California Building Code (Part 2) or California Residential Code, while operational fire-safety, water-supply and access provisions come from the California Fire Code (Part 9). The CWUIC layers ignition-resistant material requirements on top of all of that, and CALGreen and the Energy Code still apply.

Because the 2025 cycle moved provisions between parts, contractors and designers who learned the old "Chapter 7A" workflow have to re-map their references to the new Part 7 section numbers. GoCodebook identifies your parcel's fire hazard zone, the adopted edition and any local amendments, then returns the governing CWUIC provision with a citation so you can verify the original language quickly.

Wildfires ignite buildings three ways, and the code answers each one. Embers — the dominant cause of structure loss — are addressed by ember-resistant vents, non-combustible roof edges and gutters, enclosed eaves and soffits, and restrictions on gaps at roof coverings and decking. Radiant heat is addressed by exterior wall and window requirements, including multi-pane or tempered glazing. Direct flame is addressed by Class A roof assemblies and ignition-resistant or noncombustible siding, decking and projections.

Material compliance is demonstrated through Office of the State Fire Marshal (OSFM) listings and named ASTM and SFM test standards — the reason a builder cannot simply substitute a visually similar product. Section 503, ignition-resistant construction and material, is where the exterior assembly requirements live.

Existing buildings are generally not required to retrofit, but Section 507 reaches roof replacement: replacing or repairing a roof covering in a WUI area triggers the current roof requirements. That single provision converts a routine re-roof into a code-upgrade event on a large share of homes in fire-prone areas.

The CWUIC is not only about materials. Section 403 (access) and Section 404 (water supply) set road and supply requirements for development in WUI areas, and Chapter 6 covers the site conditions around the structure: fire protection plans (602), vegetation plans (603), maintenance of defensible space (604), spark arrestors (605), LPG installations (606), firewood storage (607) and building siting and setbacks (608).

Chapter 6 also reaches into land use: fire-safe development regulations (610), subdivision review (611) and the general plan safety element (612). This is why a WUI project can face requirements at the subdivision and entitlement stage, long before a building permit.

Vegetation clearance itself remains enforced in the field under state fire law and the California Fire Code, including the ember-resistant Zone 0 immediately around a structure. The construction code and the defensible-space program work together but are inspected by different people at different times.

California's adopted codes — including the California Wildland-Urban Interface Code (CWUIC) — are published under Title 24 and hosted on code libraries such as UpCodes (up.codes) and ICC Digital Codes from the International Code Council (ICC). Those let you read the text section by section.

GoCodebook goes further: instead of searching a code library, you ask a question and get the controlling provision for the edition and local amendments your jurisdiction adopted, with a citation to verify. See how GoCodebook compares to UpCodes and ICC.