Building an ADU in unincorporated Los Angeles County

Unincorporated areas only

LA County Planning says it serves "all areas outside a city in Los Angeles County," and that the county has 88 cities. Use the county's Z-NET zoning map to find your zoning and confirm the county is your planning department; areas inside a city are masked out in white.

If your property is in a city, follow that city's ADU rules. We have pages for Los Angeles, Long Beach, Pasadena, Glendale, Burbank, Santa Monica, Culver City and West Hollywood. For the statewide rules, see our California page.

In the county's Coastal Zone, ADUs follow the applicable Local Coastal Program instead of these standards. [1][2]

What you can build

The rules are in LA County Code Section 22.140.640, last amended by Ordinance 2025-0029, which took effect August 28, 2025.

Single-family lots. You can have one ADU attached to or inside the house or an accessory building, one detached ADU, and one junior ADU (JADU).

Multifamily lots. The code allows ADUs inside or attached to existing buildings, up to 25% of the units (rounded up), plus two detached ADUs. LA County Planning's own memo notes that state law (SB 1211) now allows up to eight detached ADUs on a lot with an existing multifamily building, but no more than the number of existing units.

Fire zones. On a lot in a Very High Fire Hazard Severity Zone, the county prohibits ADUs built under its local standards unless the lot has two separate means of vehicular access to a highway, each at least 24 ft wide, or fronts a highway with direct access. The smaller "state-exempt" units described below are allowed regardless of access. In any Fire Hazard Severity Zone, an ADU must be at least 200 ft from publicly dedicated open space, though an ADU of at least 800 sq ft with 4 ft side and rear setbacks is still allowed.

State-exempt units. Some ADUs are permitted subject only to a short list of standards: one ADU inside the existing space of a house or accessory building (plus up to 150 sq ft for an entrance), one new detached ADU of up to 800 sq ft with 4 ft side and rear setbacks, and the multifamily conversions and detached units allowed by state law. [2][4]

Size, height and setbacks

Size. An ADU must be at least 150 sq ft, with one habitable room of at least 70 sq ft. The maximum is 1,200 sq ft. There is no maximum for an ADU entirely within an existing home, or for a converted accessory building expanded by no more than 150 sq ft for an entrance. Community and planning area standards districts can't use their floor area or lot coverage limits against an ADU.

Height. An attached or detached ADU can be up to 25 ft. A Planning Area Standards District, Community Standards District or Specific Plan can set a lower limit, but it must allow at least 16 ft for a detached ADU, 18 ft (plus 2 ft for a matching roof pitch) within a half mile walking distance of a major transit stop or high-quality transit corridor, and 18 ft on a multifamily lot. Within 200 ft of a scenic route or highway, a new ADU can't be taller than the house or 18 ft, whichever is less, subject to those same minimums.

Setbacks. New ADUs and expanded parts of existing buildings must be at least 4 ft from the rear, interior side and corner side lot lines. No setback is required for an ADU inside an existing home, or for a conversion or same-size rebuild of an existing building. An ADU of 800 sq ft or less may go in the front yard setback if there is no other place on the property to build it at ground level.

Historic properties. On county historic landmarks, in historic districts and on Mills Act properties, extra design standards apply to locally permitted ADUs, such as matching the house's roof and window style. The state housing department (HCD) has found that some of these rules don't comply with state law; see below. [2][4][5]

Parking

Outside Very High Fire Hazard Severity Zones, no parking is required for an ADU.

Inside those zones, the normal parking rules apply unless an exception is met, in which case no parking is required. Exceptions include an ADU with no bedroom, one within a half mile walking distance of public transit, one in a historic district, one that is part of the house or an accessory building, where on-street parking permits are required but not offered to the occupant, and where a car share vehicle is located within one block.

If you tear down or convert a garage, carport or covered parking to build an ADU, you don't have to replace that parking. Where parking is required, it can be on a driveway and in tandem. [2][4]

Fees and timeline

Impact fees. State law bars impact fees on an ADU with 750 sq ft of interior livable space or less, and on a JADU of 500 sq ft or less; on larger units, impact fees must be charged in proportion to the unit's size compared with the main house. ADUs and JADUs under 500 sq ft of interior livable space are not subject to school impact fees. Utilities can't treat an ADU or JADU as a new residential use when calculating connection fees or capacity charges, unless it is built at the same time as a new single-family home; where such a fee does apply, it must be proportionate to the ADU's size or plumbing fixtures compared with the house. Plan check and permit fees depend on your project; ask Public Works Building and Safety. For typical costs see our ADU cost guide.

Timeline. The county code says a decision on an ADU or JADU application must be made within 60 days of a complete application. Under state law, the county must also tell you within 15 business days whether your application is complete. If your ADU is filed together with a new house or apartment building, the county may wait to decide on the ADU until it decides on the new building. If the county denies an application, it must return a full set of comments explaining what is wrong and how to fix it. See our ADU permit process guide. [2][4][6]

Garage conversions and junior ADUs

Conversions. You can convert an existing accessory building, such as a garage, into an ADU without setbacks if you don't expand it, and with no size cap if any expansion is 150 sq ft or less for an entrance. Since the 2025 amendment, unpermitted structures may be converted to ADUs or JADUs. ADU approval can't be conditioned on fixing nonconforming zoning conditions on the lot. Public Works also runs a Garage Conversion to ADU program with standard sheets and an expedited process. See our garage conversion guide.

Junior ADUs. One JADU is allowed per single-family lot, inside the existing or proposed house. It needs at least an efficiency kitchen and a separate entrance. If it shares the house's bathroom, it must have interior access to the house. The owner must record a covenant that bars selling the JADU separately, and the county requires the owner to live in the house or the JADU. A JADU is not permitted on a lot owned by a corporate entity. State law now requires owner occupancy only when the JADU shares sanitation facilities with the house, so if your JADU has its own bathroom, confirm with LA County Planning. See our junior ADU guide. [2][3][4][6]

Renting it out or selling it

ADUs and JADUs may be rented only for periods of more than 30 consecutive days, so short-term rentals aren't allowed. An ADU or JADU can't be sold separately from the main house, except as provided in state law (Government Code Section 66341).

You don't have to live on the property to have an ADU. The county has also released its interest in old covenants that required an owner to live in the house or ADU forever.

SB 9 and new subdivisions. The county is working on a draft 2026 ADU Ordinance Amendment, meant to clarify how county policy relates to state law and to explore options for using state-granted authority to limit ADUs on certain subdivided lots. As of July 2026 it was still a draft, no hearings were scheduled, and existing county and state rules continue to govern. Follow it on the 2026 ADU Ordinance Amendment page. See our SB 9 guide. [2][6][7]

Where the county's rules may differ from state law

In December 2025, the state housing department (HCD) reviewed the county's 2025 ADU ordinance and found that it does not comply with state ADU law in several ways. HCD said the county must:

• allow up to eight detached ADUs on a lot with an existing multifamily building, but no more than the number of existing units (the code says two),
• spell out the attached-ADU height allowance of 25 ft or the house's height limit, whichever is lower,
• remove language limiting where an ADU can go, including the front-yard rule above and the historic-property siting rules,
• remove the subjective "character-defining features" standard for historic properties, and
• reflect all the unit types state law allows.

The county could respond by amending the ordinance or by adopting findings explaining why it disagrees. Until it changes, the county code still contains these provisions. The code itself says that where it conflicts with the state ADU law, state law controls. If any of these points affects your project, cite the HCD letter and confirm with LA County Planning. [2][5]

Standard ADU Plans Program

LA County offers free plans that LA County Planning and Public Works Building and Safety have already approved. The County Catalog has three: Plan A (1,200 sq ft, 3 bedrooms, 1 bathroom), Plan B (1,200 sq ft, 2 bedrooms, 1 bathroom) and Plan C (800 sq ft, 1 bedroom, 1 bathroom). You can orient or mirror them, but you can't otherwise change them. You still need a site-specific plot plan approved by LA County Planning, plus site-specific Title 24 energy calculations and agency referral items.

A separate Private Designer Catalog lists plans by private architects and designers, which you buy and complete with the designer. Find both on the county's ADU page. [8][9][10]

Permit steps in Los Angeles County

1. Confirm you are in unincorporated LA County

   Look up your zoning on Z-NET. If your lot is inside a city, apply to that city instead. Check for fire zone, coastal zone, community standards district or historic status. [1][2]

2. Talk to a planner if needed

   LA County Planning offers virtual counseling. [9]

3. Prepare plans

   Use a County Catalog plan or custom plans. Public Works asks for complete architectural and structural plans and Title 24 energy calculations; a Catalog plan needs a site plan inserted on its first page. [3][8]

4. Get LA County Planning approval

   Submit a "DRP-Base Application-Permits and Review" online through EPIC-LA, with the plans and the items on the Land Use Checklist. A planner checks completeness, sends an invoice and reviews the application. [8]

5. Get building plan check

   Building plan check for unincorporated areas is processed online through EPIC-LA or at a local Building and Safety district office. The plan checker gives you an agency referral sheet listing other approvals you need. [3]

6. Submit agency approvals and get the permit

   Correct and resubmit plans as needed, then submit approvals from every agency on the referral sheet, including LA County Planning. The project is then ready for permit issuance. [3]

7. Build and pass inspections

   Construction starts once the permit is issued, followed by Building and Safety inspections. [3]

Pre-approved and sample plans

• Standard ADU Plans Program: County Catalog

  Three free plans pre-approved by LA County Planning and Public Works: two 1,200 sq ft designs (3 or 2 bedrooms) and one 800 sq ft design (1 bedroom). [8]

• Standard ADU Plans Program: Private Designer Catalog

  Plans by private architects and designers, pre-approved by the county, that you buy and complete with the designer. [9]

Who to call

• LA County Planning (Department of Regional Planning)

  ADU zoning rules and planning approval for unincorporated areas (info@planning.lacounty.gov)

  (213) 974-6411

  320 West Temple Street, Los Angeles, CA 90012

  [9]

• LA County Planning, Housing Policy Section

  ADU ordinance and the 2026 amendment (housing@planning.lacounty.gov)

  (213) 974-6417

  [7]

• LA County Public Works, Building and Safety

  Building plan check, permits and inspections through district offices serving unincorporated communities

  [3][10]

Questions people ask