SB 504 and AB 1455: What Changed for Zone Zero

Assembly Bill 3074 created Zone Zero in 2020, but it did not finish the job of turning a five-foot ember-resistant zone into a standard that fire agencies actually enforce. Two later bills picked up where AB 3074 left off, and they did so on very different timelines. Senate Bill 504, signed in 2024, spent four years building out the practical infrastructure the original bill needed: longer compliance windows, cleaner integration between zones, broader coverage. Assembly Bill 1455, signed in 2025, arrived on a completely different clock. It followed the January 2025 Los Angeles firestorm by months, passed as urgency legislation, and pushed the state to finish what AB 3074 started far faster than the normal rulemaking process would have allowed. For Bay Area homeowners trying to make sense of where Zone Zero stands today, these two bills are a large part of why the picture looks different, and more urgent, than it did even a year ago.

How SB 504 and AB 1455 Fit Into AB 3074’s Framework

California’s approach to Zone Zero was never a single bill doing all the work. AB 3074 set the direction: a new ember-resistant zone within five feet of a structure, defined in technical detail not by the bill itself but by the Board of Forestry and Fire Protection, working alongside CAL FIRE and the State Fire Marshal’s office. That structure, a law that sets a goal and hands the technical detail to a state agency through formal rulemaking, is exactly the kind of framework that tends to get refined through follow-on legislation rather than torn up and replaced.

SB 504 built on that framework the way most follow-on bills do: incrementally, working out compliance mechanics and jurisdictional gaps inside the system AB 3074 already created. AB 1455 is a different kind of follow-on. It operated inside the same five-foot Zone 0 boundary, but it exists because a firestorm forced the legislature’s hand, not because the rulemaking calendar reached a natural next step.

SB 504 and AB 1455 did not replace AB 3074. One kept its rulemaking moving forward. The other, passed after the January 2025 Los Angeles fires, forced it to move faster.

For the original bill and what it put in motion, see our AB 3074 explainer.

What SB 504 Changed in 2024

SB 504, signed by Governor Newsom on September 29, 2024, gave the rulemaking process concrete new tools rather than just more time to work. The bill extended the compliance deadline for existing structures from one year to three years after enforcement begins for new construction, a change that matters for any homeowner staring down a tight retrofit window. It also authorized the Board of Forestry to adjust the Zone 1 fuel-reduction rules so they integrate cleanly with the newer Zone 0 standard, and extended Zone Zero’s reach to occupied dwellings in Very High Fire Hazard Severity Zones inside Local Responsibility Areas, not just the state-managed areas AB 3074 originally covered.

None of that rewrites the five-foot boundary itself. What it does is make the standard livable at the edges: more time to comply for existing homes, less friction between the zone closest to the structure and the zones beyond it, and a wider set of properties brought under the same rule.

What AB 1455 Changed in 2025

AB 1455 is a different animal. Signed October 13, 2025, it arrived roughly nine months after the Los Angeles firestorm that destroyed thousands of homes in Pacific Palisades and Altadena, and the legislature treated it accordingly. This was urgency legislation, meaning it took immediate effect rather than following the standard delayed schedule most bills follow.

The bill implements Governor Newsom’s Executive Order N-18-25, issued in the fire’s aftermath, which directed the Board of Forestry and Fire Protection to finish Zone 0’s technical regulations through emergency rulemaking, a faster track than the multi-year process the state would normally use, with a target completion date of December 31, 2025. AB 1455 amends Government Code Section 51182 and adds Section 51182.4, giving the state a clearer statutory basis for the compliance and penalty framework fire agencies use once the regulations are final.

That target date has already come and gone. As of mid-2026, the Board of Forestry’s Zone 0 regulations are still in draft, not final. The most recent version, released in spring 2026, leans toward education and outreach ahead of penalties for the initial enforcement period. AB 1455 changed the urgency behind the rulemaking. It has not yet changed the fact that the technical standard itself is still being finished.

How Local Fire Agencies Are Enforcing These Combined Requirements

None of these three bills enforces itself. That job falls to the Authority Having Jurisdiction, usually shortened to AHJ: the local fire department or building department responsible for a given address. AB 3074 set the direction, SB 504 extended timelines and cleaned up how zones interact, and AB 1455 put the state on an emergency track toward finishing the technical rules. But the actual inspection, the actual compliance notice, and the actual deadline a specific homeowner receives still come from whichever AHJ covers that property.

That is why two Bay Area homes a few miles apart can sit on genuinely different Zone Zero timelines even though all three bills apply statewide. Some Bay Area fire districts have used the added clarity and urgency from SB 504 and AB 1455 to move ahead of the state’s own default schedule, writing local requirements that call for Zone Zero compliance sooner than the pending state regulation might otherwise demand. Others are still waiting for the Board of Forestry to finalize its Zone 0 standards, which as of mid-2026 remain in draft, before writing anything new into local code.

The Expanded Definition of Defensible Space

Defensible space in California has always been built in layers: Zone 0 closest to the structure, Zone 1 reaching further out, Zone 2 covering the outer band of a property. AB 3074 added Zone 0 to a framework that already existed. SB 504 is the bill that did the technical work of making that addition fit: it authorized the Board of Forestry to adjust the Zone 1 fuel-reduction rules so they integrate with the newer, stricter Zone 0 standard, closing gaps that surfaced once fire agencies started applying all three zones to the same property at the same time.

For a homeowner, the practical result is less about a bigger number on a map and more about fewer inconsistencies between the zone closest to the house and the zones further out. A fence, a woodpile, or a planting bed sitting right at the boundary between Zone 0 and Zone 1 is less likely to fall into a gap where neither standard clearly applies. For the full breakdown of what each zone actually requires, see our Zone Zero explainer, and our complete defensible space guide covers how Zones 0, 1, and 2 work together across a full property.

Timeline Implications for Homeowners Today

These three dates do not describe one steady, unhurried march toward a fixed finish line. AB 3074 set the direction; SB 504 spent four years building the infrastructure around it; then a firestorm changed the pace entirely, and AB 1455 compressed what might have been another multi-year rulemaking cycle into an emergency track with a hard deadline.

That deadline, December 31, 2025, has already passed without final regulations. As of mid-2026, Zone 0’s technical standards remain in draft. What has not changed since 2020 is the destination: a fully enforced, non-combustible five-foot zone around the structure. What has changed is the urgency behind finishing the job, and how many AHJs have stopped waiting on the state and started enforcing their own version of Zone Zero in the meantime.

For the specific phase your property is likely in right now, our Zone Zero compliance timeline tracks how the state regulation and local adoption have progressed since AB 3074 first passed.

What Three Bills Add Up to for a Bay Area Homeowner

Reading AB 3074, SB 504, and AB 1455 as three unrelated mandates misses the point, but so does reading them as one calm, continuous project. A slow build followed by a crisis-driven sprint is a different story than three evenly-paced bills, and it is the true one. For a homeowner planning fence replacement or landscaping work near the house, the practical takeaway has not changed since AB 3074 first passed: the five feet closest to the structure needs to be free of combustible material. What has changed is how much regulatory pressure now sits behind finishing that standard, and how much less patience the state has for treating it as optional.

Confirming your local AHJ’s current enforcement status, rather than assuming the statewide legislative timeline applies exactly to your address, is still the most useful thing a homeowner can do with this information. Our fire hazard zone lookup tool is the fastest way to confirm which severity zone applies to a specific property before making that call. With Zone 0’s technical regulations still in draft as of mid-2026, that local check matters more than ever. Documented compliance under this timeline is also increasingly something insurers weigh at renewal; see our Zone Zero and insurance guide for what to keep on file.

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