Your City's WUI Overlay May Stop Triggering the State WUI Code

Here's a scope question that's about to get sharper: does the state WUI code reach a parcel because the city drew it into a local “WUI area,” or because the parcel sits in a fire hazard severity zone? For some hillside cities, those are two different maps — and the final text would make the zone map the one that counts.

What the code says today

The California Wildland-Urban Interface Code (Part 7 of Title 24) has applied since January 1, 2026. Its application section, §101.3.1, lists four kinds of land where the code's rules kick in:

1. All State Responsibility Area (SRA) land;
2. LRA land the State Fire Marshal identifies as High or Very High Fire Hazard Severity Zone;
3. High or Very High zones designated by cities and other local agencies; and
4. Land designated as a Wildland-Urban Interface Area by cities and other local agencies.

Chapter 2 backs up item 4 with a definition that sweeps in “…other areas designated by the enforcing agency to be at a significant risk from wildfires.”

Verified against the 2025 California WUI Code as it reads today — §101.3.1 item 4 and the §202 definition of “Wildland-Urban Interface Area.”

That item 4 is the hook for a city's own WUI overlay. If your jurisdiction mapped a “WUI area” broader than its fire hazard zones, item 4 is what pulls those extra parcels into state Part 7.

What the final text would change

The State Fire Marshal's certifying rulemaking for Part 7 (SFM 04/25) went before the Building Standards Commission at its August 25-27, 2026 meeting. The final express terms would strike item 4 and rewrite the “Wildland-Urban Interface Area” definition so it no longer reaches “other areas designated by the enforcing agency.”

The Marshal's own reasoning is blunt: the term “WUI areas” is overly broad, does not match statutory terminology, and can be interpreted inconsistently across jurisdictions. Under the proposed definition, a WUI area is land in a Fire Hazard Severity Zone in the SRA, LRA land the Marshal identifies as High or Very High, or LRA land a local agency designates High or Very High under Government Code §51179(b).

Here's the asymmetry that matters: in the SRA, every FHSZ level counts — including Moderate. In the LRA, only High and Very High do. So a Moderate zone inside a city (LRA) is exactly the parcel that would fall out of state scope once item 4 is gone.

LRA High isn't the new part

Don't misread this as “the code just added High zones.” It didn't. LRA High coverage is already in the emergency supplement in force today (§101.3.1 item 2). The change is the removal of the local “WUI area” path — item 4 — and the definition that fed it.

The route the code now points to

Alongside the deletion, the final text adds a new §302.3, “Local designation,” which restates the Government Code rule for cities. Government Code §51179(a) requires a local agency to “designate, by ordinance, moderate, high, and very high fire hazard severity zones in its jurisdiction within 120 days of receiving recommendations from the State Fire Marshal.” And the statute runs one direction: a local agency “shall not decrease the level of fire hazard severity zone” the Marshal set, and may only increase it.

Read together, that's the path for a city that wants the state code to reach a parcel its old overlay covered: designate the land High or Very High under §51179(b). A Moderate designation won't carry it in the LRA.

This is not the overlay going “void”

Important nuance: deleting item 4 doesn't erase a city's WUI overlay or the ordinance built on it. What changes is that state Part 7, on its own, would no longer reach parcels that sit only inside a local “WUI area.” A city keeps two routes to hold that ground: bump the parcels to High or Very High under §51179(b), or adopt a local amendment with the climatic, geological, or topographical findings that Health & Safety Code §§17958.7 and 18941.5 require. Home-hardening amendments to Part 7 are one of the few residential categories a city can still newly adopt. See Can a city make Title 24 stricter?.

Not everyone wanted item 4 gone. A group of fire officials writing as California Code Professionals asked the Marshal to modify item 4 rather than delete it, so cities could still designate added areas — like Moderate zones in the LRA — by ordinance consistent with §51179(b)(2). The Marshal's response: it “will continue to evaluate and identify opportunities for reducing wildfire risk.” The local path stayed out of the final text, for now.

The action item

For city fire and building staff: audit your local WUI overlay against your adopted FHSZ ordinance while it's still a proposal. If it's adopted, any parcel the overlay covers but the ordinance leaves at Moderate — or unmapped — in the LRA is the gap. For designers: stop asking whether a parcel sits in the city's WUI overlay and start asking whether it's in a designated High or Very High zone. When it's close, confirm the zone and check whether the city adopted the new maps — then verify with the jurisdiction before you rely on it.

What CrossBeam does with it

CrossBeam reads WUI scope the way the code actually draws it — zone first, overlay second — so a review tells you whether a parcel sits in a Fire Hazard Severity Zone that triggers Part 7, not just whether it falls inside a local line. When the state text changes what counts, that shift shows up where you're checking the plan.