Los Angeles County ADU rules and requirements

Yes, if your property is in unincorporated Los Angeles County, meaning outside every city's limits, you can build an ADU on a lot with a house or apartments. A new detached unit can be 1,200 sq ft, and can be 25 ft tall. No parking is required unless you are in a Very High Fire Hazard Severity Zone. County fees run about $6,500 to $7,600 for planning approval plus building plan check and permit on an 800 sq ft unit, and Regional Planning has 60 days to decide once your application is complete and paid. A mailing address that says Los Angeles, Altadena or Whittier does not tell you whose rules apply; the county's Z-NET map does.

Detached unit: Up to 1,200 sq ft¹²
Parking: None outside fire zones¹²
County fees, 800 sq ft: About $6,500 to $7,600⁶⁸⁷
Decision: Within 60 days¹¹³

Figures read from the city's own documents, last checked 20 September 2026. Each number links to its source.

Who to call: Los Angeles County Department of Regional Planning, 213-974-6411. Field offices at the county Building and Safety district offices (Altadena One-Stop, 464 W. Woodbury Rd Suite 210; East Los Angeles, 4801 E. Third St; La Puente, 16005 E. Central Ave; Arcadia, 125 S. Baldwin Ave; Southwest, 1320 W. Imperial Hwy; Calabasas; Santa Clarita; Lancaster). The downtown counter at 320 W. Temple St is closed; applications go through EPIC-LA online.. info@planning.lacounty.gov.¹⁹³⁴

Under state review. The county adopted a new ADU ordinance in July 2025, and the state housing department found six problems with it in December 2025. The ordinance is in effect, but where it is stricter than state law the county has said its staff memos and state law win, and a further amendment is being drafted for 2026.¹²¹⁴¹⁵¹³

The rules at a glance

"City rule" means Los Angeles County set the figure. "State rule" means the city applies the state minimum, which no city can go below.

ADU rules in Los Angeles County
Backyard unit, max size City rule	1,200 sq ft of interior living space for a new detached unit, on a single-family or a multifamily lot. Converting a garage or other permitted building has no size cap, and you can add up to 150 sq ft for an entry or stairs. A unit with an attached garage that together exceed 1,200 sq ft needs fire sprinklers. The county measures the interior habitable space, not the footprint.¹⁵¹³
Attached unit, max size City rule	Half the living area of the existing house, up to 1,200 sq ft, and never less than 800 sq ft. Inside an existing house or apartment building there is no cap.¹¹⁴
Junior unit, max size State rule	500 sq ft inside the existing house or its attached garage, with at least a small kitchen. It needs a recorded covenant before plans are approved. Not allowed on multifamily lots or on lots owned by a corporation.¹²⁴
Height City rule	25 ft for a new attached or detached unit on a lot with a house, unless a Community Standards District, planning area or specific plan sets a lower limit, and even then the county must allow 16 ft, or 18 ft plus 2 ft of roof pitch within a half-mile walk of a major transit stop. Within 200 ft of a scenic route the unit cannot be taller than the house or 18 ft, whichever is lower. Converting an existing building has no height limit.¹¹²
Setbacks City rule	Four feet from the rear and side property lines for anything new. A converted garage keeps its existing setback, and a garage rebuilt in the same spot to the same size can too. A unit of 800 sq ft or less may sit in the front setback if there is nowhere else on the lot to put it. Eaves and other projections may come no closer than 2.5 ft to the line. Building and Safety wants a detached unit at least 6 ft from the house, or else the wall facing it must be fire rated, and any wall within 5 ft of a property line must be fire rated.¹⁵
Parking City rule	None, unless your lot is in a Very High Fire Hazard Severity Zone. There the county asks for one uncovered space, but waives it if the unit has no bedroom, is a detached unit of 800 sq ft or less and 16 ft or under, is a conversion, is within a half-mile walk of transit, is in a historic district, or is on a block with a car-share vehicle. Removing a garage, carport or even an uncovered space to build the unit never requires replacement parking. Any space you do need can be tandem or on the driveway.¹²¹⁶
Lot coverage and open space City rule	Community Standards District and specific plan limits on floor area, structural area and lot coverage do not apply to an ADU. State law also bars any local limit that would stop an 800 sq ft unit with 4 ft setbacks. Grading review kicks in on slopes steeper than 1 to 3, digs over 50 cubic yards, and when you add more than 50 percent to the lot's paved area.¹¹⁷⁵
Do you have to live there State rule	No, not for an ADU; the county has released the old covenants that required it. For a junior unit the owner must live in the house or the junior unit, unless the junior unit has its own bathroom, in which case the requirement no longer applies since January 2026.¹¹³¹⁷
Renting it out State rule	Tenants must stay 30 days or longer; nightly rentals are not allowed. The unit cannot be sold separately from the house. A new ADU falls under the county's rent stabilization ordinance for eviction and relocation rules but is exempt from its rent caps.¹⁷¹⁴

Los Angeles County ADU permit fees

City permit fees
Regional Planning ministerial site plan review (the ADU planning approval)	$1,496 for a residential site plan; $1,995 in a Community Standards District, hillside or similar special district; $1,765 in the coastal zone Regional Planning Revised Filing Fees, effective March 1, 2026, items 62, 69 and 70⁶
Building plan check and building permit, new 800 sq ft detached unit	Set by construction valuation, which the plan check engineer assigns. Formula for the permit: $1,930.69 plus $9.99 per $1,000 over $100,000, plus 10 percent for energy code work; plan check is a separate table amount. Worked example at a $200,000 valuation: $2,739.52 plan check, $3,248.96 permit, $41.35 issuance and about $65 plan maintenance, roughly $6,100. At $150,000 it is about $5,060. Building Permit and Plan Checking Fees table and Table 1-A, effective July 1, 2026⁸⁹⁷
Permit issuance and certificate of occupancy	$41.35 to issue the permit; $151.50 for the certificate of occupancy at the end Building Code Fee Schedule, effective July 1, 2026, items 1 and 11⁷
Standard plan minimum plan check	$225.59 when you use one of the county's three pre-approved plans Building Code Fee Schedule, effective July 1, 2026, item 20⁷
Extra plan check rounds	$164.02 per hour after the second check when corrections are yours Building Code Fee Schedule, effective July 1, 2026, item 10⁷
School district fee and Sanitation District connection fee	Charged by those agencies, not the county. The school fee applies only over 500 sq ft of new space. Both receipts are required before the building permit issues; no county figure is published. Building and Safety ADU Guidelines v4.1, agency requirements⁵

How long it takes

Plan on two reviews in sequence: Regional Planning's 60 days, then a separate Building and Safety plan check with its own correction rounds, then clearances from Fire, the school district, the Sanitation District and your water company before the permit issues. Building and Safety publishes no typical plan check time.¹³⁴²¹¹⁸

Completeness check: 15 business days for Regional Planning to tell you whether your application is complete, or it is deemed complete
Decision: 60 days after that, once the planning fee is paid, to approve or deny the planning application
Pre-approved plans: Same 60-day clock; the plans themselves are already approved so review is the site plan

Does an ADU fit your lot in Los Angeles County?

The rules above are the city's. Whether they work on your lot depends on the lot. Type your address and we tell you yes, no, or yes with conditions, then connect you with one licensed builder who works in Los Angeles County. Free, and nobody calls unless you ask.

Check my address

Things to know before you build in Los Angeles County

Check the jurisdiction before anything else. Altadena, Hacienda Heights, Rowland Heights, East Los Angeles, Florence-Firestone and Willowbrook are county territory, but a Los Angeles or Whittier mailing address can be either. Type your address into the county's Z-NET map; if the lot is inside a city, that city's rules apply and this page does not.
The county's three free plan sets are the cheapest route. Download Plan A, B or C, have someone draw the site plan onto the first sheet, and file it in EPIC-LA. Building and Safety's minimum plan check for a standard plan is $225.59 instead of a full valuation-based check.
Two departments, two applications. Regional Planning approves the site plan first, through EPIC-LA, and you have two years to take that approval to Building and Safety for the building permit. Building and Safety then hands you an agency referral sheet: Fire, the school district (over 500 sq ft), the Sanitation District and your water company all have to sign off before the permit issues.
In a fire zone, size decides access. A unit built to the state exemption, 800 sq ft and 16 ft tall with 4 ft setbacks, is allowed on any lot. Going bigger or taller triggers the county's two-road access rule, which many canyon lots fail.
A garage conversion with no added footprint can use the county's standard notes and details instead of engineered plans, but you must book a pre-construction meeting with the inspector when the permit issues or the permit is revoked.

Overlays that change the answer

Very High Fire Hazard Severity Zone. A locally sized unit (up to 1,200 sq ft, 25 ft) needs two separate paved routes to a highway, each 24 ft wide, or a lot fronting directly on a highway. An 800 sq ft, 16 ft unit under the state exemption is allowed regardless of access. One parking space unless an exemption applies, fuel modification, sprinklers if the house has them, and the unit must be 200 ft from public open space.¹²⁵²⁰
Coastal Zone (Santa Monica Mountains and other coastal areas). The Local Coastal Program's rules replace section 22.140.640, and the planning fee is $1,765.¹²⁶
Prohibited areas. No locally sized ADU on lots between Old Topanga Canyon Road, the coastal boundary, Calabasas and the City of Los Angeles, or on Santa Monica Mountains lots reached only from Lobo Canyon or Triunfo Canyon Road. The state-exemption unit is still allowed.¹
Community Standards Districts, planning area standards and specific plans. A lower height cap can apply, but never below 16 ft (18 ft near transit). Their floor area and lot coverage limits do not apply. Planning fee rises to $1,995.¹⁶
County historic landmarks, historic districts and Mills Act properties. The unit must match the house's roof, siding, windows and doors, cannot use vinyl windows, cannot be taller than the house, and goes behind it where possible.¹
Hillside Management Area and scenic routes. Within 200 ft of a scenic route the unit is capped at the house's height or 18 ft. On slopes steeper than 1 to 3, Public Works drainage and grading review is added.¹⁵

Pre-approved ADU plans in Los Angeles County

Available Three county-owned plan sets are free to download and already approved by Regional Planning and Building and Safety: Plan A, 1,200 sq ft with three bedrooms; Plan B, 1,200 sq ft with two bedrooms; Plan C, 800 sq ft with one bedroom, all single-story and updated for the 2025 building codes. You add a site plan to the first sheet, file through EPIC-LA, and a planner checks it, invoices you and reviews within the normal 60 days. Building and Safety charges its standard-plan minimum plan check of $225.59 plus the permit. A second catalog of private designers' plans is offline until those designs are updated to the codes that took effect 1 January 2026.¹⁰¹¹³⁷

Questions people ask

Is my property in unincorporated Los Angeles County?

Only if it sits outside every city's limits. A postal address such as Los Angeles, CA or Altadena, CA does not settle it; Altadena is unincorporated, but much of what is addressed Los Angeles or Whittier is inside a city. Look the parcel up on the county's Z-NET map, or call Regional Planning at 213-974-6411.

How big can an ADU be in unincorporated LA County?

A new detached unit can be 1,200 sq ft of interior living space. An attached unit can be half the house's living area up to 1,200 sq ft, and at least 800 sq ft is always allowed. Converting a garage or another permitted building has no size cap. A junior unit inside the house can be 500 sq ft.

How tall can an ADU be in LA County?

25 ft for a new unit on a lot with a house, unless a Community Standards District or specific plan sets a lower cap, and even then at least 16 ft, or 18 ft plus 2 ft of roof pitch within a half-mile walk of major transit. Near a scenic route the cap is the house's height or 18 ft.

Do I need parking for an ADU in LA County?

Not unless the lot is in a Very High Fire Hazard Severity Zone. There the county asks for one uncovered space, waived for a conversion, a detached unit of 800 sq ft and 16 ft or less, a unit with no bedroom, or a lot within a half-mile walk of transit. Tearing out a garage to build the unit never requires replacement parking.

How much are ADU permit fees in LA County?

Regional Planning charges $1,496 for the site plan review ($1,995 in a Community Standards District or hillside area). Building and Safety's plan check and permit depend on the construction valuation the plan checker assigns; at $150,000 to $200,000 for an 800 sq ft unit that is roughly $5,100 to $6,100, so about $6,500 to $7,600 in county fees before school, sanitation and utility charges.

Does LA County have pre-approved ADU plans?

Yes. Three county plans are free: 1,200 sq ft with three bedrooms, 1,200 sq ft with two bedrooms, and 800 sq ft with one bedroom. You add a site plan and file in EPIC-LA. A catalog of private designers' plans is offline until those plans are updated to the 2025 codes.

What changed

1 July 2026 Building and Safety fees rose 3.4 percent with the FY 2026-27 schedule.
29 April 2026 Regional Planning reissued its ADU Ordinance Summary.
1 March 2026 Regional Planning filing fees changed; the residential ministerial site plan review is now $1,496.
1 January 2026 SB 543 and AB 1154 took effect. The county's 30 December 2025 memo applies the 15-business-day completeness check, appeals to the Regional Planning Commission, measurement by interior living space, and drops the junior-unit owner-occupancy rule where the junior unit has its own bathroom. The private designer plan catalog went offline pending updates to the 2025 codes.
1 December 2025 HCD found Ordinance 2025-0029 out of compliance with state ADU law on six points, including unit counts on multifamily lots, the height subsection, front-setback siting language and a subjective historic-preservation standard.
28 August 2025 Ordinance 2025-0029 took effect: state-exemption units allowed in fire zones regardless of road access, uniform 1,200 sq ft cap for attached units, 25 ft height, front-setback allowance for units of 800 sq ft or less, one parking space in fire zones unless exempt.
1 January 2025 SB 1211 and AB 2533 took effect. The county's 25 November 2024 memo allows up to eight detached ADUs on existing multifamily lots and no replacement parking for any removed space. AB 2533 lets unpermitted units built before 2020 be legalized; Public Works issued manuals for it.

Sources

Ordinance No. 2025-0029, amending section 22.140.640 (Accessory Dwelling Units and Junior Accessory Dwelling Units), adopted July 29, 2025, County of Los Angeles Board of Supervisors. Accessed 20 September 2026.
Accessory Dwelling Unit (ADU) Summary, revised April 29, 2026, Los Angeles County Department of Regional Planning. Accessed 20 September 2026.
Accessory Dwelling Units page, Los Angeles County Department of Regional Planning. Accessed 20 September 2026.
Step-by-Step Guide for Accessory Dwelling Units in the County of Los Angeles Unincorporated Areas (April 5, 2023), Los Angeles County Department of Regional Planning and Public Works. Accessed 20 September 2026.
ADU and JADU Building and Safety Guidelines, v4.1, October 10, 2024, Los Angeles County Public Works, Building and Safety Division. Accessed 20 September 2026.
Revised Filing Fees, effective March 1, 2026, Los Angeles County Department of Regional Planning. Accessed 20 September 2026.
Building Code Fee Schedule, effective July 1, 2026 (FY 2026-27 County Building Code Fees), Los Angeles County Public Works, Building and Safety Division. Accessed 20 September 2026.
Building Permit and Plan Checking Fees for Unincorporated County Area (valuation table), effective July 1, 2026, Los Angeles County Public Works, Building and Safety Division. Accessed 20 September 2026.
Table 1-A Building Permit Fees (Fees from Ordinance), effective July 1, 2026, Los Angeles County Public Works, Building and Safety Division. Accessed 20 September 2026.
Standard ADU Plans Program, County Catalog, Los Angeles County Department of Regional Planning. Accessed 20 September 2026.
Standard ADU Plans Program, Private Designer Catalog, Los Angeles County Department of Regional Planning. Accessed 20 September 2026.
Review of Los Angeles County's Accessory Dwelling Unit Ordinance under State ADU Law, findings letter, December 1, 2025, California Department of Housing and Community Development. Accessed 20 September 2026.
Informational memo, Accessory Dwelling Units: Senate Bill 543 and Assembly Bill 1154, December 30, 2025, Los Angeles County Department of Regional Planning. Accessed 20 September 2026.
Informational memo, Accessory Dwelling Unit Ordinance Amendment, August 21, 2025, Los Angeles County Department of Regional Planning. Accessed 20 September 2026.
2026 ADU Ordinance Amendment project page, Los Angeles County Department of Regional Planning. Accessed 20 September 2026.
Informational memo, Accessory Dwelling Units / SB 1211, November 25, 2024, Los Angeles County Department of Regional Planning. Accessed 20 September 2026.
Government Code sections 66310 to 66342, ADU law (link opens at section 66314), State of California. Accessed 20 September 2026.
Government Code section 66317, permit timelines (SB 543), State of California. Accessed 20 September 2026.
Locations and Office Hours, Los Angeles County Department of Regional Planning. Accessed 20 September 2026.
County of Los Angeles Very High Fire Hazard Severity Zone and Accessory Dwelling Units, Letter of Technical Assistance, June 22, 2023, California Department of Housing and Community Development. Accessed 20 September 2026.
ADU/JADU page, permit steps and pre-approved garage conversion criteria, Los Angeles County Public Works, Building and Safety Division. Accessed 20 September 2026.

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Educational guidance drawn from the city's published rules, not a permit determination or a quote. Rules change; the date at the top is when these were last checked. Spotted a wrong figure? Tell us.