# California's New WUI Code (Title 24 Part 7): What Changed in 2026

> Since January 1, 2026, California's wildfire construction rules are in a standalone California Wildland-Urban Interface Code (Title 24, Part 7), based on the 2024 International WUI Code. It replaced CBC Chapter 7A and CRC Section R337. Exterior walls can comply through noncombustible, ignition-resistant, tested or fire-rated assemblies, among other paths.

Source page: https://apbmetalstudbuilders.com/learn/california-wui-code-2026
Publisher: APB Inc. (CSLB #951030)
Last updated: 2026-10-20

California reorganized its wildfire building rules for the 2025 code cycle. For homeowners and architects working on rebuilds or new homes in fire-prone areas, the practical question is what moved, what the exterior wall rules now say and how to confirm what applies to a specific lot.

This page summarizes what we can confirm from public sources. Section numbers should be checked against the official Title 24 text before you rely on them, and we say below which points we have not verified.

## What changed in California's wildfire building code in 2026?

The 2025 California Building Standards Code took effect statewide on January 1, 2026. It includes a new, standalone **California Wildland-Urban Interface Code**, published as Title 24, Part 7.

- **Where the rules live.** Wildfire construction requirements used to be in California Building Code Chapter 7A and California Residential Code Section R337. They are now in Part 7.
- **What it is based on.** Part 7 is based on the 2024 International Wildland-Urban Interface Code (IWUIC), with California amendments.
- **Where building construction rules sit.** LA County's 2026 construction notes cite Part 7 Chapter 5, with exterior covering requirements in Section 504.5, vents in 504.10 and windows in 504.8.
- **Local amendments carry over.** Cities and counties can still add local requirements. San Diego's proposed amendments, for example, carry its earlier local additions to Chapter 7A and R337 (noncombustible drip edge flashing, reinforced vinyl windows) into its adoption of Part 7.

### Which code applies to your project

The code in effect on your permit application date generally governs. A project submitted under the 2022 codes in 2025 may still be reviewed under Chapter 7A or R337, and most projects submitted in 2026 are reviewed under Part 7.

Fire rebuilds are the main exception. Executive Order N-29-25 lets homes rebuilt after the January 2025 Eaton and Palisades fires comply with the 2022 California Building Standards Code instead of the 2025 edition, according to LA County's implementation sheet. In that case the wildfire rules come from Chapter 7A or R337, not Part 7. Section numbers and some requirements differ between the editions, so tell your designer which edition you are using.

If you are revising an existing permit, for example switching a wood-frame plan to steel, ask your building department whether the revision keeps the original code edition or triggers the new one. We have not found a published answer that covers every jurisdiction.

## Before and after at a glance

| Topic | Before 2026 | From January 1, 2026 |
|---|---|---|
| Where wildfire construction rules live | CBC Chapter 7A and CRC Section R337 | California Wildland-Urban Interface Code, Title 24 Part 7 |
| Model code basis | California-specific chapters | 2024 IWUIC with California amendments |
| Exterior wall requirements | Chapter 7A / R337 | Part 7 Section 504.5 (per LA County notes) |
| Local amendments | Amended Chapter 7A / R337 | Amend Part 7 |
| Which edition applies | Code in effect at permit application | Same rule; Eaton and Palisades rebuilds may use the 2022 code under EO N-29-25 |
| Zone 0 (first five feet) | Not in effect | Still not in effect as of October 2026 |

## What does Part 7 require for exterior walls?

LA County's 2026 construction notes list the following options for the exterior wall covering or wall assembly (Section 504.5):

- 1-hour fire-resistance-rated construction on the exterior side
- Noncombustible material
- Ignition-resistant material
- Heavy timber construction
- Log wall construction
- An assembly complying with ASTM E2707 and SFM Standard 12-7A-1
- An assembly with one layer of 5/8-inch Type X gypsum sheathing behind the exterior wall covering, on the exterior side of the framing
- An assembly with a 1-hour fire-resistance rating from the exterior side, tested to ASTM E119 or UL 263
- Fire-retardant-treated wood labeled for exterior use

The same notes require at least 6 inches of metal flashing or noncombustible material at the base of the wall where it meets the ground, decks and roofs, and they state that paints, coatings and stains are not an approved method of protection.

### Does the WUI Code require steel framing?

No. Noncombustible exterior walls are one of several compliance paths, not a requirement. These rules address the **exterior covering or assembly**. Steel studs are noncombustible — they don't burn or add fuel — but they do not make combustible siding compliant on their own. A steel-framed house still needs a compliant covering or assembly, along with compliant roofs, vents, eaves and windows.

For how framing compares with the rest of the envelope, see [Steel Framing for Wildfire Rebuilds: What It Does and Doesn't Do](/learn/steel-framing-wildfire-rebuild). Code compliance sets the minimum; the IBHS Wildfire Prepared Home Plus standard goes further, with noncombustible siding, enclosed eaves, covered gutters and upgraded windows.

## Fire hazard severity zone maps

Part 7 construction requirements apply to new buildings in Fire Hazard Severity Zones and in Wildland-Urban Interface areas designated locally, and to additions, alterations and repairs in those areas, according to LA County's 2026 notes.

- **State maps.** CAL FIRE maps Fire Hazard Severity Zones (moderate, high and very high) for State and Local Responsibility Areas.
- **2025 local maps.** CAL FIRE released updated Local Responsibility Area maps for Los Angeles County on March 24, 2025.
- **Local adoption.** Cities and counties adopt the local maps by ordinance, and they can add areas. The adopted local map is what your building department uses.

## How do I check if my lot is in a fire hazard severity zone?

1. **Run a quick [address check](/check)**, which reads CAL FIRE's Fire Hazard Severity Zone maps, the 2025 Eaton and Palisades fire perimeters and your energy climate zone.
2. **Confirm on CAL FIRE's map viewer** on the [Office of the State Fire Marshal's Fire Hazard Severity Zone page](https://osfm.fire.ca.gov/fhsz).
3. **City of Los Angeles:** look up your parcel in [ZIMAS](https://zimas.lacity.org/), which shows hazard designations along with zoning.
4. **Unincorporated LA County (including Altadena):** LA County Public Works' 2026 Fire Hazard Severity Zone construction notes include a link to the County's map.
5. **Other cities:** ask the local building or fire department which map and ordinance they use.
6. **Confirm with your plan checker.** Maps change, and the designation on your permit is the one that counts.

## What we have not verified

We want to be clear about the limits of this summary:

- **Section numbers.** The numbers above come from LA County's 2026 construction notes and the San Diego code change report, not from our own review of the adopted Part 7 text. Check them against the official code.
- **Mid-cycle amendments.** State agencies can amend Part 7 between full code editions. We have not tracked every proposed change, so check for updates before you finalize drawings.
- **Revisions to existing permits.** Whether a revision triggers the new code is decided by each building department.
- **Fire-rebuild code edition.** How each jurisdiction applies the 2022-code option under EO N-29-25, and whether it covers a redesign from wood to steel, should be confirmed with your plan checker.
- **Local map adoption status.** We have not confirmed which LA-area cities have adopted the 2025 local maps or the dates.
- **Zone 0.** The Board of Forestry adopted emergency Zone 0 rules on August 19, 2026 and submitted them to the Office of Administrative Law on August 28. It withdrew them from review in early September 2026 (reported September 11). They are not in effect as of October 2026, and no resubmission date has been announced.

## What this means for homeowners and architects

- Design the whole envelope to Part 7: roof, vents, eaves, windows, exterior covering and the base of the wall.
- Confirm your lot's hazard designation and which code edition applies before finalizing drawings.
- If you are switching an existing wood plan to steel, plan for a structural revision and an energy update. Our [wood-to-steel plan conversion](/plan-conversion) page explains that process.

Rebuilding after the January 2025 fires? See our guides for [Altadena](/rebuild/altadena) and [Pacific Palisades](/rebuild/pacific-palisades), or [contact APB Inc.](/contact) with your address and plans.

## Why homeowners choose steel framing with APB

The WUI Code sets the minimum for the exterior. Many owners who rebuild in fire areas choose to go beyond it, with a noncombustible steel structure under a hardened exterior that is designed to a standard such as Wildfire Prepared Home Plus. We build the steel package to whichever code edition your project is reviewed under and coordinate with your architect on the exterior. Read [why steel framing pays off in California](/why-steel), see how [plan conversion](/plan-conversion) works, or [contact us](/contact).

## Common questions

### When did the new California WUI Code take effect?

The 2025 California Building Standards Code, including the new Wildland-Urban Interface Code (Part 7), took effect statewide on January 1, 2026. The code in effect on your permit application date generally governs, but Eaton and Palisades fire rebuilds may use the 2022 code under Executive Order N-29-25.

### Does the WUI Code require steel framing?

No. The exterior wall rules apply to the wall covering or wall assembly, and noncombustible material is one of several accepted paths. Steel studs are noncombustible, but they do not make a combustible exterior covering compliant on their own.

### Is Chapter 7A still in the building code?

For projects under the 2025 codes, the wildfire construction provisions formerly in CBC Chapter 7A and CRC Section R337 are now in Part 7, as LA County's 2026 construction notes state. Projects still reviewed under the 2022 codes, including some fire rebuilds, use Chapter 7A or R337.

### How do I know if my lot is in a fire hazard severity zone?

Use our address check or CAL FIRE's Fire Hazard Severity Zone map viewer, then confirm with your city or county, since local maps are adopted by ordinance. In the City of Los Angeles, ZIMAS shows parcel-level information; in unincorporated LA County, start with Public Works.

### Are Zone 0 rules part of the new code?

Not as of October 2026. Zone 0 is a separate Board of Forestry regulation under AB 3074. The Board adopted emergency rules in August 2026, then withdrew them from Office of Administrative Law review in early September, and no resubmission date has been announced.

## Sources

- [California Building Standards Commission: Codes](https://www.dgs.ca.gov/bsc/codes)
- [City of San Diego: 2025 California Wildland-Urban Interface Code change report](https://www.sandiego.gov/sites/default/files/2026-02/2025-cwuic_code-change-report.pdf)
- [LA County Building and Safety: Fire Hazard Severity Zone construction notes (2026 code)](https://dpw.lacounty.gov/bsd/lib/fp/Building/Very%20High%20Fire%20Hazard%20Severity%20Zone/2026%20Code%20Version/Fire%20Hazard%20Notes%202026.pdf)
- [CAL FIRE Office of the State Fire Marshal: Fire Hazard Severity Zones](https://osfm.fire.ca.gov/fhsz)
- [City of Los Angeles: ZIMAS parcel information](https://zimas.lacity.org/)
- [WildfireLA: Zone 0 regulations withdrawn from OAL review (Sept. 11, 2026)](https://www.wildfirela.org/2026/09/11/zone-0-regulations-withdrawn-from-oal-review-what-happens-next/)
- [Best Best & Krieger: Board of Forestry adopts emergency Zone 0 regulations under AB 3074](https://bbklaw.com/resources/la090926-california-board-of-forestry-adopts-emergency-zone-0-regulations-under-ab-3074)
- [LA County: Executive Order N-29-25 implementation sheet](https://file.lacounty.gov/SDSInter/lac/1191301_ExecutiveOrderN-29-25ImplementationSheet.pdf)