The requirements

What Zone 0 actually requires

Zone 0 is not a bare five-foot strip. It is two nested areas with different rules, and it permits more planting than most summaries suggest — within tight limits on size, spacing and species type.

Where Zone 0 starts and stops

Zone 0 is the area within five feet around each structure, beginning at the exterior surface of the exterior wall, roof, attached deck, stairs or pergola, and extending five feet out — or to the property line, whichever comes first.

Inside that five feet sits a smaller vegetation-free buffer, sometimes called the safety zone. It is defined by three separate measurements, and you take whichever is largest at any given point:

At least one foot from the wall, or out to the edge of the eave if the eave is deeper — up to a maximum of five feet
At least two feet from windows, doors and vents
At least five feet from any attached deck, stairs or pergola

So a house with 12-inch eaves has a 12-inch buffer along a blank wall. A house with 30-inch eaves has a 30-inch buffer. Around a deck it is the full five feet everywhere.

The LRA version adds one word. 14 CCR 1298.04(b)(6) lists windows, doors, posts, or vents. The SRA version at 1299.03(d)(6) omits posts. If you have porch posts within Zone 0 and you are in a Local Responsibility Area, the two-foot buffer applies to them.

What is banned outright

Except as specifically permitted, no combustible materials anywhere in the full five feet. The rule names fallen leaves and tree needles, combustible mulches including bark and woodchips, and other combustible debris. Also:

Roof and rain gutters kept clear of leaves, needles and combustible debris
Areas underneath decks, balconies, pergolas and stairs kept free of vegetation and combustible items
No firewood stored in Zone 0

Inspectors may allow temporary exceptions to the mulch limits to prevent erosion during construction and during emergencies — a carve-out that exists to keep the rule compatible with stormwater pollution prevention requirements.

Plants: what you can keep

Outside the vegetation-free buffer but still inside the five feet, planting is allowed if it meets one of three conditions. All three require non-woody plants — the regulation's term for herbaceous plants with soft green stems.

Option	Size limit	Conditions
Low ground cover and lawn	Under 3 inches tall	Well maintained, free of dead or dying material
Small plantings	3 to 18 inches tall	Each planting no more than 1 square foot in area; spaced from each other by 1.5 times the height of the tallest plant
Potted plants	Up to 18 inches tall	Unaffixed noncombustible pots, no larger than 5-gallon capacity; spaced by 1.5 times the plant height

The two versions define "non-woody" differently. The LRA definition at 1298.02(g) includes annuals, perennials, bulbs, grasses, ferns, mosses and some succulents. The SRA definition at 1299.02(h) lists only bulbs, annuals, grasses and mosses. The same plant may qualify on one side of the line and not the other. If you are relying on ferns or succulents, check which definition governs you.

Trees

Existing trees may stay in Zone 0. The regulation regulates maintenance rather than removal. Trees in Zone 0 must be maintained so that:

There are no dead or dying branches
All live branches are at least 10 feet from chimneys and stovepipe outlets
Live branches are not underneath eaves
All ladder fuels are removed — the first 6 feet from the ground, or the lower third of the tree's height, whichever is smaller, plus fuels within 5 feet above a roof that create a high risk of fire transmission
Live branches are at least 5 feet above a roof, and at least 1 foot from walls where there is no eave

What counts as a "Tree" is narrower than you think. The regulation defines a Tree as a woody perennial with a well-defined stem or trunk, a diameter of at least 4 inches measured 4.5 feet above the ground, and a mature height of at least 15 feet.

Anything smaller is not a Tree for these purposes. It gets no tree allowance — and since the planting rules permit only non-woody plants, a small woody shrub or ornamental tree in Zone 0 has no category that allows it. This will catch a lot of people out.

New trees

The Board's summary states that no new trees may be planted in Zone 0. The rule text contains no such prohibition. The cover memo explains why: staff will add language about new trees to the 2026 Guidance Document to align with the California Wildland-Urban Interface Code, rather than to the regulation.

So the restriction is real but it lives in the building code and forthcoming guidance, not in Zone 0. Anyone reading only the summary will state this incorrectly.

Fences and gates

Combustible fences and gates shall not be attached to a structure.
Any fence or gate that is attached, or comes within one foot of contact, must have a five-foot noncombustible span from the point of attachment or the closest point.
After the effective date, no new combustible fences or gates within five feet.
Repairs to an existing combustible fence may be made using combustible replacement materials.

Two discrepancies worth knowing. First, the LRA version at 1298.04(b)(9)(B) bars new combustible fences "whether attached or parallel to" the structure. The SRA version at 1299.03(d)(9) omits that phrase.

Second, the Informative Digest in the Notice says repairs may be made "with noncombustible materials." The rule text says the opposite — combustible replacement materials are permitted for repairs. Where a digest and the rule text conflict, the rule text controls, but expect confusion on this point.

Outbuildings

An Outbuilding — under 120 square feet, not used for human habitation — is not permitted in Zone 0 unless it is constructed entirely of noncombustible materials.

What "noncombustible" means

This is defined, not left to ordinary meaning. Noncombustible means materials that pass the ASTM E136 test, meeting the standard described in Section 501.4.1 of Title 24, Part 7 of the California Wildland-Urban Interface Code.

Practically: verify a product against the Office of the State Fire Marshal's Building Materials Listing and WUI Products Handbook before you buy. A product marketed as fire-resistant is not the same as a product that passes E136.

Local agencies can vary this

14 CCR 1298.03 lets a local agency in the LRA develop alternative practices accounting for local variation — fire risk, lot size, structure density, exterior composition, topography, response capability, or compliance with the WUI building code. Those alternatives must be approved by the city council or board of supervisors and supported by a finding that they deliver substantially similar practical effects.