Number of ADUs Allowed in the City of Los Angeles
- Maximum size: 1,200 sq ft (detached or attached, or 50% of the size of the main dwelling)
- Side/rear setbacks: 4 feet
- Two story: Yes, for both attached and detached ADUs
- Building separation: 6 feet
- Soils Report: Possibly, especially in areas with grading or on hillsides
- Building Verification Survey: Yes
- Coastal permit (in some areas): N/A
- Stormwater Mitigation: Yes
Number of ADUs Allowed in Unincorporated Los Angeles County
On single-family residential lots in unincorporated Los Angeles County, you may buildone attached ADUorup to two detached ADUson your property. You can also build up toone JADUinto the existing primary residence.
Multifamily property owners in unincorporated Los Angeles County may build up totwo detached ADUs on the property. They may also convert an unlimited number of existing non-residential structures or uninhabitable space within existing structures into ADUs or JADUs.
ADU Unincorporated Los Angeles County – Size & Building Constraints
In unincorporated Los Angeles County, the maximum size your detached ADU can be is1,200 square feet. For multifamily lots, the maximum size can vary depending on the lot size. A 1-bedroom detached ADU must typically be a minimum of 850 square feet; a 2-bedroom detached ADU, a minimum of 1,000 square feet.
In unincorporated Los Angeles County, the maximum size your attached ADU can be is1,200 square feet, or50% of the size of the main dwelling unit, whichever number issmaller.
In unincorporated Los Angeles County, conversion of existing structures into ADUs carry no height restriction.
For new-construction detached ADUs, the height must be less than16 feet. For attached ADUs, the maximum height requirement is typically limited to the height of the primary dwelling unit.
In unincorporated Los Angeles County, detached ADUs are not necessarily restricted from being two stories, but the height limitation of 16 feet makes it functionally impossible, or at least very difficult, to get approval of two-story plans. Attached ADUs might be approved if attached to taller main structures with enough clearance for a second story.
In unincorporated Los Angeles County, detached ADUs are not necessarily restricted from beingstacked one on top of the other, but the height limitation of 16 feet makes it functionally impossible, or at least very difficult, to get approval of two-story plans. Attached stacked ADUs might be approved if attached to taller main structures with enough clearance for a second story.
Unincorporated Los Angeles County does allow two ADUs to be attached to each other, provided the lot has enough space, the plans conform to all applicable regulations, and zoning rules allow it.
No, a JADU is defined as an ADU converted from existing space within the main structure of the primary dwelling unit. As such, it cannot be attached to an ADU.
Generally roof decks would be permitted, but must meet the height restrictions for the zone. Roof decks cannot encroach into the required setbacks. Generally railings and access staircases above 42″ need to be included in height calculations.
Unincorporated Los Angeles County makes no mention of specific requirements for the exterior of the ADU. However, general guidance is that the exterior roofing, trim, walls, windows and the color palette of the ADU shall incorporate the same features as the primary dwelling unit.
ADU Setbacks in Unincorporated Los Angeles County
In the Los Angeles County, side and rear setback requirements for an ADU are at least 4 feet. All other setbacks must comply with ordinary zoning setback requirements. No additional setback requirements apply to existing structures that are converted into ADUs.
Los Angeles County rules stipulate a minimum separation of 6 feet between structures within a lot, so your new detached ADU must be a minimum of 6 feet from the main house and any other structures.
No, an ADU must be built in the back or side yard of residential property in unincorporated Los Angeles County.
ADU Setbacks in Unincorporated Los Angeles County
No, unincorporated Los Angeles County doesnotrequire in-person submission of plans for an ADU. The Los Angeles County Building and Safety Department provides a web portal for online submission of plans known as EPIC-LA that allows the upload of digital plans for review.
Not always. Los Angeles County typically only requires a soils report for ADU plans on properties situated on a slope or a hillside, or if the site presents other geotechnical concerns.
If you are building an ADU in a coastal zone or within a designated landslide or geo-hazard zone, Los Angeles County may require you to pull coastal development permits (CDP) for your ADU project.
ADU landscaping is generally required to blend into existing landscaping and enhance the overall aesthetic appeal. Rules for limitations of non-permeable surfaces, as well as requirements for the planting of drought-resistant vegetation and the preservation of existing trees.
To receive permits for your ADU, plans must be submitted to the Los Angeles County Building and Safety Department for preliminary review. The plans must then be sent to a variety of other County departments for clearance. The basic process is as follows:
- Submitting initial plans and fees
- Initial review of plans for correctness and obvious issues
- Detailed departmental reviews (structural, zoning, fire safety, utility, environmental, etc.)
- Corrections and re-submission
- Final approval
From submission to approval, average turnaround time is 4-6 months. For complicated plans (coastal development zones, historical zones, etc.) it can take as long as a year or more.
The Los Angeles County Building and Safety Department may send inspectors periodically to check the progress of the project and verify that it is being constructed to plan.
Parking for Unincorporated Los Angeles County ADU
The parking requirements for residential property areone additional parking spot per ADU. Properties located within ½ mile of walking distance from a public transit stop or station may be exempt from parking requirements.
If a garage or carport is replaced with an ADU, property owners must maintain a number of off-street parking spaces commensurate to the number of parking spaces eliminated by the garage conversion, though those spacescanbe uncovered.
If a parking space is required, it may be located within the setbacks and in an existing driveway as tandem parking. Parking spaces don’t need to be replaced when a garage, carport, or covered parking structure is demolished in conjunction with the construction of an ADU or converted to an ADU.
Additional Requirements in Unincorporated Los Angeles County
Most newly constructed ADUs must comply with California Title 24 Building and Energy Efficiency Standards. If you submitted your permit application later than January 1, 2020, this means you must provide solar panels on new ADUs to offset their reliance on the grid. This does not necessarily mean the solar panels need to be installedonthe ADU itself. They can be installed on the primary dwelling unit or a new or existing array.
No, a separate electric and water meter is not required for an ADU. However, you may request one from the city.
Not necessarily. An ADUcanbe permitted under the existing address. If you want your ADU to have its own address, you can apply to the Mapping and Property Management Division (MPM) for a “½” address designation. In other words, if your address is 1234 Elm Street, your ADU could have a separate address of “1234½ Elm Street.”
If the ADU has its own driveway or direct street access, a new addresswillbe required.
Low Impact Development (LID) is an approach to land development or redevelopment that seeks to preserve and conserve onsite water quality and natural features, with minimal detrimental effect to local waterways and ecosystems. Unincorporated Los Angeles County requires LID for ADUs of 500 square feet or more.
As of September 2024, ADUs can only be used as a short-term rental or Airbnb in unincorporated Los Angeles County if the unit is the owner’s primary residence — meaning the owner must actually live in the ADU. Rentals are limited to 30 consecutive days or less, and owners must register the rental with the L.A. County Treasurer and Tax Collector (TTC) and pay a fee.
Rentals in Los Angeles County are subject to the Los Angeles County Rent Stabilization and Tenant Protections Ordinance (RSTPO), which may or may not apply to your ADU.
If your ADU was built after January 1, 1995, RSTPO will most likely not apply. It also will most likely not apply if the ADU is built on a property that includes the owner’s primary residence. Even if the ADU is built on property thatissubject to RSTPO, RSTPO may not apply to the ADU unless specifically mentioned in local regulations or amendments.
You can use gas appliances in an ADU in unincorporated Los Angeles County as long as all building codes, safety standards, and installation guidelines are adhered to. The proper permits must be obtained, and requirements for safety and ventilation observed.
The Los Angeles Fire Department requires that all dwellings over 1,200 square feet, including an attached garage, have automatic fire sprinklers. Since ADUs are limited to 1,200 square feet in unincorporated Los Angeles County, your ADU is unlikely required to have fire sprinklers.
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