Explainer

What is Zone 0? California's ember-resistant zone, explained

Fact-checked August 19, 2026·Sources at the end of this article

The five-foot zone, defined

Stand at any exterior wall of your house and measure five feet out. That strip of ground is Zone 0. The measurement starts from the exterior wall, the roof, or an attached deck, stairs, or pergola, and extends five feet, or to the property line, whichever comes first. The August 2026 package narrowed the definition of an occupied structure on this point: an attached deck, stairs or pergola counts as part of the structure even when it is built of noncombustible materials, and only noncombustible patios are left out. On a house with an attached deck, that means the five feet are measured from the edge of the deck rather than from the wall behind it.

Regulators call it the ember-resistant zone. The idea is simple: keep the first five feet free of things an ember can ignite. Combustible material in that strip (mulch, firewood, plants, attached wood fences) gives embers something to catch. The complications are in the rule's legal status, its coverage, and its details, so let's take those in order.

Why five feet: the ember science

Most homes lost in wildfires are ignited by wind-driven embers landing on or near the house, not by a wall of flame. Governor Newsom's executive order on the subject puts it plainly:

"Scientific research has shown that the greatest risk of embers directly or indirectly igniting a home... stems from combustible materials built or planted within five feet of a home, including perpendicular wood fences and combustible landscaping."

Executive Order N-18-25, February 6, 2025

Fences earn a specific mention because of how they burn. NIST fire researchers describe a fence line fed by mulch or dry vegetation as a "wick": it carries flame toward the structure and holds it there. The pattern showed up after the January 2025 Palisades and Eaton fires, when IBHS surveyors walked the burn areas: on the parcels they examined, more than 95% had a fence, most were wood (about 65%), and roughly 6 in 10 fences were attached to the home or stood inside the first five feet. More on the research in why fences burn homes.

The same investigation asked the harder question, which is whether any of it changed the outcome. IBHS assessed more than 250 properties between January 13 and 19, 2025 and published the results as The 2025 LA Conflagrations. Its finding on the first five feet:

"more than 25% fuel coverage in Zone Zero pushed the risk of damage or destruction to nearly 90%"

Insurance Institute for Business & Home Safety, news release on the Palisades and Eaton Fire findings

Two things about that are worth reading carefully, because they cut in different directions. It is the strongest published evidence that the first five feet decide outcomes, and it is measuring fuel coverage, not fence material. IBHS describes the fuel as "vegetation and everyday items like hot tubs, patio furniture and trash bins," which "repeatedly served as connective fuels that carried fire to vulnerable building features." Nothing in that release isolates fences, and we are not going to pretend it does. What it establishes is that clearing the zone matters a great deal, and that the cheapest things in it, a bin and a patio chair, are part of the problem.

It also found that hardening works as a system rather than a checklist item: homes with four key features, "a Class A roof, noncombustible siding, double-pane windows and enclosed eaves," had a 54% likelihood of avoiding damage, "compared to just 36% when only a single action was taken." A single measure is worth something. It is not worth what four are.

Where Zone 0 comes from: AB 3074, PRC §4291, and an executive order

Three documents explain the term's legal history:

• AB 3074 (2020). This bill amended Public Resources Code §4291, California's defensible space statute, to require an ember-resistant zone within five feet of a structure, "based on regulations promulgated by the board." The statute created the mandate; the Board was left to write the rules.
• SB 504 (2024), the statute the histories skip. Chaptered September 29, 2024 as Chapter 982, this Dodd bill amended both defensible-space statutes, PRC §4291 and Government Code §51182, and it is where the existing-home phase-in comes from. Its words, identical in effect on both tracks: the ember-resistant zone requirement "shall take effect for existing structures three years after the effective date for the new structures." Note what that says and what it does not: three years, both tracks. The adopted regulation splits the clocks, three years in the Local Responsibility Area extendable to five, five in the State Responsibility Area shortenable to no less than three. The LRA regulation matches its statute; the SRA regulation's five-year figure is the regulation's own number, sitting on top of a statute that says three. We track that mismatch on the open questions page.
• Executive Order N-18-25 (February 6, 2025). Issued the month after the Palisades and Eaton fires, it directed the Board to complete the Zone 0 rulemaking by December 31, 2025. The Board did not meet that deadline; it declined to vote in December 2025 and paused work into early 2026.
• The 2026 drafts and the adopted package. The Board released a draft on April 17, 2026 and a revised draft in July 2026, discussed at a July 23 workshop, then acted on an August 19, 2026 package. Between the April and July drafts, the fencing language tightened: the word "parallel" was added to the new-fence prohibition in the Local Responsibility Area text (that clause appears only there, not in the State Responsibility Area version), and a formal ASTM E136 definition of "noncombustible" was added. The Board's own August summary describes that addition as drawn from the California Wildland-Urban Interface Code, which is consistent: the WUI code's noncombustible test is ASTM E136. The fence provisions did not change again in August.

The Board approved the regulation on August 19, 2026. The next step is the Office of Administrative Law, which reviews the package (a five-day public comment period is provided during that review) before the Secretary of State publishes it. Two further conditions sit in the statute rather than the rulemaking calendar: section 4291(g)(1) withholds effect for new structures until the Board updates the guidance document as well as the regulations, and section 4291(h) withholds any change to inspection practices and forms until the State Fire Marshal certifies that the Legislature appropriated the money. The tracker follows both. Staff said they would submit an emergency rulemaking package under AB 1455 (2025) immediately upon approval, and that the rules "could become effective as early as September 2026." That schedule is not guaranteed; the December 2025 deadline was also a schedule, once.

How Zone 0 fits into Zones 1 and 2

Zone 0 does not replace California's defensible space system. It is a new, stricter layer inside it. PRC §4291 already defines two zones, and Zone 0 sits inside the first:

If you already maintain defensible space, Zone 0 is the same logic pushed to the final five feet, where an ember's odds of reaching the house are highest.

Is Zone 0 the law right now?

Statewide: not yet. The Board of Forestry approved the regulation on August 19, 2026, which is a real milestone, and it is still not in effect. The package has to clear the Office of Administrative Law, a review that includes a five-day public comment period, and then be published by the Secretary of State. No statewide compliance deadline is running, because every deadline in the rule runs from "the effective date of these regulations," and that date does not exist yet. Anyone telling you the state rule binds your property today is ahead of the facts. The status tracker follows the rulemaking as it moves.

Locally: in at least thirty-five jurisdictions, yes:

• Ventura County Fire Protection District: full noncombustible Zone 0 effective March 1, 2025 for new buildings, additions, and new or refurbished landscaping (new-building Zone 0 requirements since April 1, 2019); covers all of Ventura County except the cities of Ventura, Oxnard, and Fillmore.
• City of Laguna Beach: Ordinance 1664, a Zone 0 defensible space guideline in force for all existing structures in its Very High zone (about 85% of the city) since November 5, 2021.
• Moraga-Orinda Fire District (Contra Costa County): in force since March 17, 2023 for all structures in the district.
• City of Auburn (Placer County): in force since July 10, 2024, for new construction.
• City of Berkeley: the "EMBER" ordinance, effective January 1, 2026, in the Grizzly Peak and Panoramic hillside mitigation zones.
• City of San Diego: in force for new structures since February 28, 2026; the phase for existing structures begins February 28, 2027.

One large city is moving the other way: in January 2026, the Los Angeles City Council directed LAFD to draft deliberately more lenient Zone 0 rules. No LA ordinance has been adopted, and the contested provisions concern vegetation and tree limbs, not fences. Details on each program are in the local ordinance roundup and the San Diego Zone 0 guide.

Which homes the statewide rule covers

Not every California home is covered. The regulation reaches two areas under two different statutes, and the difference is widely misunderstood:

So a home in a Moderate hazard zone inside an SRA falls under the regulation, while a home in a High hazard zone inside an LRA does not. Per the Board of Forestry FAQ and CAL FIRE, that works out to roughly 1.25 million structures in the SRA plus 870,000 in LRA Very High zones: about 2.12 million structures, or 17% of all structures statewide.

The maps behind this changed recently: California updated the LRA Fire Hazard Severity Zone maps between February 10 and March 24, 2025, the first update since 2011. Local agencies must adopt the zones by ordinance and may add area, so local coverage can be broader than the state map. You can look up a specific address on the CAL FIRE / OSFM Fire Hazard Severity Zone maps; our walkthrough does Zone 0 apply to my home? shows how to read the result.

Why the coverage figures disagree, and why they mostly don’t

Reporting on the rule has carried at least four different numbers for how much of California it reaches. They look like a contradiction. Almost all of it is a units problem, and once you line them up they tell a consistent story.

Two things are being counted, and two different denominators are being divided by. A structure is not a home: the structure count includes buildings that nobody lives in. And 17% is a share of all structures, while 10% is a share of the state’s housing stock, which the Department of Finance put at about 15.1 million units as of January 1, 2026. Divide 1.75 million homes by that and you get roughly 12%, which is the same neighborhood as the reported 10%. Neither outlet is wrong; they are answering different questions.

The one real difference is that CAL FIRE’s own homes estimate appears to have come down, from about 2 million in the September 2025 FAQ to 1.75 million in the August 2026 reporting. We have not found a published explanation for the change and we are not going to invent one.

What we use, and why. This site cites 2.12 million structures, about 17%, because that is the figure CAL FIRE states in the Board’s own FAQ, in the units the regulation is written in. The regulation applies to structures, not to households. If you want a sense of how many families it touches, the homes figures are the better guide, and they land between 1.75 and 2 million.

What Zone 0 means for fences and gates

Fences get their own numbered provisions, and they came through the August package unchanged from the July draft. In summary, the regulation requires the following. None of it is a duty you owe today: the rule was adopted August 19, 2026 and is not yet in effect.

• Attached fences and gates: any fence or gate attached to an occupied structure, or coming within one foot of it, needs a five-foot noncombustible span from the point of attachment. Combustible fences and gates may not be attached to the structure.
• New fences: after the effective date, no new combustible fence or gate is permitted within five feet of the structure. The Local Responsibility Area text spells out that this covers fences "whether attached or parallel to the Occupied Structure"; the State Responsibility Area version carries no parallel clause. A full replacement of a fence within Zone 0 counts as new.
• Existing fences: an existing fence passing through Zone 0 but not attached to the structure may remain, and repairs to an existing combustible fence may use combustible replacement materials.
• Beyond five feet: nothing changes.

One caution about the exact wording: the August 19 package posted in the board binder is the pre-meeting deliberative draft. Amendments made from the floor would not appear in it, and no certified "as adopted" text has been published yet, so treat provision-level wording as the Board's published language with the certified version still pending.

Board staff said it directly in their July 2026 memo to the Board:

"The purpose of the regulations is not to require wholesale replacement of existing wood fences. Existing combustible fences may remain, repairs using existing materials may continue, and only where an attaching combustible gate exists or a fence is fully replaced would the applicable Zone 0 standards apply."

Board of Forestry staff, July 2026 Zone Zero clarification memo

"Noncombustible" has a precise meaning in the rule: materials that pass ASTM E136, a vertical tube furnace test at 750 °C. In practice, aluminum, steel, wrought iron, chain link, masonry, concrete, and stone pass; wood, vinyl, composite, and fire-retardant treated wood do not. Our materials guide goes through the options.

Timing matters too: for existing homes, fences sit in Phase 2 of the phase-in, and the two tracks are opposite. Local Responsibility Area, three years from the effective date and up to five on the local fire agency's timeline; State Responsibility Area, five years, and the Director may shorten it but not below three. New construction will have to comply on the effective date itself. No calendar dates exist yet, because there is no effective date yet. The full provision-by-provision breakdown is in Zone 0 fence requirements; for the complete picture, start with the California Zone 0 fencing guide.

What this means for you

If you just heard the term Zone 0, here is the honest to-do list as of August 19, 2026:

• Check whether you are covered. Look up your address on the CAL FIRE / OSFM Fire Hazard Severity Zone maps. If you are outside the SRA and outside an LRA Very High zone, the statewide regulation does not reach you.
• Check your local rules. If you are in the Ventura County Fire Protection District, Laguna Beach, the Moraga-Orinda Fire District, Auburn (new construction), Berkeley's designated hillside zones, Montecito (new buildings and additions), or a Very High Fire Hazard Severity Zone inside San Diego city limits, Zone 0 rules are already in force where you live.
• Do not rush to demolish anything. The statewide rule is adopted but not in effect, no compliance clock has started, and even once it does start, existing fences may remain and repairs may use wood.
• If you are building or fully replacing a fence near the house, plan for noncombustible in the first five feet. That choice matches what the adopted regulation requires and meets the noncombustible-materials measure that California insurers have been required to credit since October 2022 under the Safer from Wildfires regulation (a rating credit, not a requirement). Details in our insurance discounts guide.
• Watch the OAL filing. The vote is done; the effective date now depends on Office of Administrative Law review (including a five-day public comment period) and Secretary of State publication. Staff have named September 2026 as the earliest possibility, and that is an expectation, not a schedule you can rely on.