In Los Angeles, a new detached accessory dwelling unit's side-yard number and exterior wall sit in different books. State law caps the setback a local agency may require at four feet — a ceiling on the agency, not a distance the project is owed — and routes the unit into the local building code, sprinklers dropped where the primary residence needs none. The residential code then prices that relief: an unsprinklered building reads against the stricter of two exterior-wall tables, whose relief lines begin a foot further out. Wildfire construction sits in a third code; a mapped Los Angeles zone adds a fourth list.
Key numbers
| Figure | What it governs | Section |
|---|---|---|
| Four feet | Side/rear setback cap | § 66314(d)(7) |
| ≥ 5 feet, 5 feet | Unrated wall, unlimited openings | Table R302.1(1) |
| 3 feet | Both lines, sprinklered | Table R302.1(2) |
| ≥ 2 feet to < 5 feet, 1 hour, 0 hours | Projection band; eave with fireblocking | Table R302.1(1) |
| One hour, 1/4 inch, Class A | Utilities, attic screen, roof | § 91.7207 |
Four feet is a ceiling on the city
Government Code § 66314(d)(7) caps the setback for a unit not converted from an existing structure: "a setback of no more than four feet from the side and rear lot lines shall be required" — a maximum on the local agency, not a figure the project is owed. (d)(8) requires "Local building code requirements that apply to detached dwellings." (d)(12) prints the sentence this chain turns on:
Accessory dwelling units shall not be required to provide fire sprinklers if they are not required for the primary residence.
The sprinkler answer picks the table
California Residential Code § R302.1 prices it: exterior walls of dwellings and accessory buildings "shall comply with Table R302.1(1) based on fire separation distance," or with Table R302.1(2) where the building is sprinklered throughout. Their relief lines sit a foot apart: Table R302.1(1) prints "Walls | Not fire-resistance rated | 0 hours | ≥ 5 feet" and unlimited openings at five, the sprinklered table both at three, so four feet reaches neither line on the first; the rows read here carry no four-foot line.
The eave is the exception, printed as a band: "Projections | Fire-resistance rated | 1 hour on the underside, or heavy timber, or fire-retardant-treated wood | ≥ 2 feet to < 5 feet". Four feet sits inside it.
The wildfire section is a forwarding address
California Residential Code § R337 is the section a practitioner opens for wildfire construction, and its whole body is a relocation note: "Provisions for materials and construction methods for exterior wildfire exposure are now located in Part 7, California Wildland-Urban Interface Code." Opening it and stopping retrieves a pointer.
How the wildfire code reaches it
California Wildland-Urban Interface Code § 101.3.1 applies to new buildings in a designated zone "as well as new buildings and structures accessory to those applicable buildings." Section 101.3.1.1 hands the designation to cities: "Land designated as a Very High Fire Hazard Severity Zone by cities and other local agencies."
In Los Angeles the zone is a map
Los Angeles Municipal Code § 91.7201.2 declares the Very High Fire Hazard Severity Zone "a Fire District," fixed by "the boundaries shown on the Very High Fire Hazard Severity Zone Map" adopted by the City Council. Where that boundary falls on a parcel is for the design professional and the jurisdiction. § 91.7203.1 is the hinge: "every building located in a fire district shall conform to the requirements of this division."
Where the cheaper lane is, and what it costs
Two lanes are printed, each naming its price. The first is the sprinkler relief: Government Code § 66314(d)(12) says units shall "not be required to provide fire sprinklers if they are not required for the primary residence," and § R302.1 prints the price — Table R302.1(1)'s relief lines begin at five feet against Table R302.1(2)'s three.
The second lane is the eave. Table R302.1(1) footnote a.: "The fire-resistance rating shall be permitted to be reduced to 0 hours on the underside of the eave overhang if fireblocking is provided from the wall top plate to the underside of the roof sheathing." The price is that fireblocking, top plate to sheathing; footnote b. offers the same on a rake overhang, paid in attic venting.
What this looks like on the drawing
The chain lands on Los Angeles Municipal Code § 91.7207. § 91.7207.1 requires "all under-floor areas completely enclosed to the ground with construction as required for exterior walls," excepts an underside protected as for one-hour fire-resistive construction, and carves back out: "The area under cantilevered balconies and unroofed walking decks need not be considered as under-floor area, provided exposed utilities, pipes or other mechanical devices are not located in the area." § 91.7207.2 encloses under-floor utilities to one-hour fire-resistive construction; § 91.7207.3 asks for "a maximum 1/4-inch noncombustible and corrosion-resistant screen" on attic openings; § 91.7207.4 requires a Class A roof, and "Wood shakes and shingle are not permitted in the VHFHSZ."
Currency
Government Code § 66314 was amended by Stats. 2025, Ch. 67, Sec. 109 (AB 1170), effective January 1, 2026 — inside 24 months, so confirm the effective date; 2026 edition, updated 2026-09-22. § R302 and § R337 come from the 2025 California Residential Code, updated 2026-10-24; § 101 from the 2025 California Wildland-Urban Interface Code, updated 2026-10-19 — state codes with no ordinance-history line, so an edition is on record and no per-section amendment date.
The Los Angeles sections are the Los Angeles Building Code's 2026-08 edition, updated 2026-09-23: § 91.7201.2 by Ord. No. 185,587 (7/16/18); § 91.7207's title by Ord. No. 176,943 (10/5/05), its .3 and .4 by Ord. No. 179,324 (12/10/07) — none inside 24 months. No amendment line was recorded for § 91.7203.1, so that date is not established.
Frequently asked questions
Does a four-foot separation buy an unrated wall?
Not on the unsprinklered table. Table R302.1(1) prints an unrated wall only at five feet or more, and unlimited openings at five; Table R302.1(2), sprinklered, prints both at three feet. Four feet stands outside the first table's relief lines.
State law caps the side setback at four feet — can the city add more?
The cap runs the other way: Government Code § 66314(d)(7) reads "a setback of no more than four feet from the side and rear lot lines shall be required" — a limit on the local agency, not a distance the project is owed. § R302.1 is a state standard applying by fire separation distance and sprinkler status.
Can the code text say whether a lot is inside the zone?
No — it states a boundary. Los Angeles Municipal Code § 91.7201.2 fixes the zone by "the boundaries shown on the Very High Fire Hazard Severity Zone Map." Inside one, § 91.7203.1 applies: "every building located in a fire district shall conform to the requirements of this division."
Sources
- Government Code § 66314 — ADU ordinance contents: https://gocodebook.com/library/us/ca/ca-gov-66310-adu-jadu-law/title-7.-planning-and-land-use-65000-66499.58/division-1.-planning-and-zoning-65000-66345.4/chapter-13.-accessory-dwelling-units-66310-66342/article-2.-accessory-dwelling-unit-approvals-66314-66331/66314#66314
- California Residential Code § R302 — Fire-Resistant Construction: https://gocodebook.com/library/us/ca/ca-residential-code/chapter-3-building-planning/section-r302-fire-resistant-construction#R302
- California Residential Code § R337 — Exterior Wildfire Exposure: https://gocodebook.com/library/us/ca/ca-residential-code/chapter-3-building-planning/section-r337-materials-and-construction-methods-for-exterior-wildfire-exposure#R337
- California Wildland-Urban Interface Code § 101 — Scope and General Requirements: https://gocodebook.com/library/us/ca/ca-wui-code/chapter-1-administration/section-101-scope-and-general-requirements#101
- Los Angeles Municipal Code § 91.7201 — General: https://gocodebook.com/library/us/ca/los-angeles-building/division-72/sec.-91.7201.-general#91.7201
- Los Angeles Municipal Code § 91.7203 — General Requirements: https://gocodebook.com/library/us/ca/los-angeles-building/division-72/sec.-91.7203.-general-requirements#91.7203
- Los Angeles Municipal Code § 91.7207 — Special Requirements for the Very High Fire Hazard Severity Zone: https://gocodebook.com/library/us/ca/los-angeles-building/division-72/sec.-91.7207.-special-requirements-for-the-very-high-fire-hazard-severity-zone#91.7207
Related reading: Building in California Fire Country: The Rules: https://gocodebook.com/blog/2025-california-wui-code-guide
Code text quoted as published in GoCodebook's library on 2026-09-13 and re-checked against the library on 2026-10-27. This article does not replace permit review or professional judgment.