If you own a home in unincorporated Los Angeles County, the LA County ADU guidelines let you add an accessory dwelling unit on most residential lots through a ministerial permit process, with the county required to approve or deny a complete application within 60 days using fixed objective standards.1California Legislative Information. California Government Code – 65852.2 These rules only apply outside city limits. If your address falls within Pasadena, Long Beach, the City of Los Angeles, or any other incorporated city, that city’s own ADU ordinance governs instead, and the county standards below do not apply to you.
Which Lots Qualify
Title 22 of the Los Angeles County Code controls where ADUs are allowed. Parcels zoned R-A, R-1, R-2, R-3, R-4, and R-5 all qualify for full ADUs and junior ADUs through a Site Plan Review.2Los Angeles County Department of Regional Planning. Los Angeles County Code Title 22 Planning and Zoning On a single-family lot, you can build one full ADU plus one junior ADU. Multi-family lots can host additional ADUs based on a percentage of the existing units on the property.
Confirm two things before you spend money on design. First, that your lot sits in unincorporated county territory, which is what makes LA County Planning your reviewing agency.3Los Angeles County Planning. Los Angeles County Planning Second, that your zoning falls into one of the eligible categories. The county’s Z-NET tool lets you look up both.4Los Angeles County Planning. Find My Zoning
Size, Height, and Setback Limits
The physical rules depend on whether your ADU is detached, attached to the primary home, or a conversion of existing interior space.
- Detached ADUs can go up to 1,200 square feet of floor area, regardless of the size of the primary home.
- Attached ADUs are capped at 50 percent of the primary dwelling’s floor area, but the county must allow at least 800 square feet even if that percentage would produce a smaller number.
- Side and rear setbacks are four feet from property lines for new construction.
- Height is generally capped at 16 feet for detached ADUs. Units near major transit stops or on multi-family lots can reach 25 feet.
Parking is waived when the ADU is within half a mile of public transit, inside a historic district, or built within an existing structure. ADUs under 800 square feet are largely exempt from local design restrictions, which shortens the review path. Larger units are expected to remain visually secondary to the primary residence in scale and style.5LA County Planning. Accessory Dwelling Units
The county also runs a Standard ADU Plans Program with pre-reviewed architectural designs. Using one skips most of the design review on the plans themselves, though you still need site-specific documents showing where the unit sits on your lot.
Junior ADU Rules
A junior ADU is a smaller unit carved out of the existing footprint of your primary home: a converted bedroom, garage, or other attached space, capped at 500 square feet. Because it uses existing walls and roof, construction cost is usually a fraction of a full ADU.
Owner-occupancy is where junior ADUs differ most from full ADUs. Under AB 976, which took effect January 1, 2025, California eliminated owner-occupancy requirements for full-size ADUs, so you can rent both the main house and the ADU without living on the property. Junior ADUs still generally require the owner to live in either the main home or the junior unit. That requirement is waived under AB 1154 if the junior ADU has its own separate bathroom facilities.
If you build a junior ADU, the county requires you to record a Covenant and Agreement against your property title. It runs with the land, binding future owners, and memorializes both the occupancy rule and the unit’s status as a junior ADU.
Fire Hazard Severity Zones
Lots inside a Very High Fire Hazard Severity Zone face additional access rules. The county’s ordinance has required two separate vehicular routes from the lot to a public road, each with pavement at least 24 feet wide, and the two routes cannot overlap. If the lot also sits in a Hillside Management Area, both routes must be paved and maintained by Public Works.6California Department of Housing and Community Development. County of Los Angeles Very High Fire Hazard Severity Zone and Accessory Dwelling Units – Letter of Technical Assistance
One exception: lots fronting directly onto a public highway, with vehicle access that doesn’t rely on a shared private road, can qualify with a single point of access. The California Department of Housing and Community Development has challenged the broader restrictions, so enforcement may shift. If your property is in a fire zone, call LA County Planning before paying for design work.
Fees and the 750-Square-Foot Exemption
Plan check and building permit fees apply to every project and vary with scope. Water and sewer connection fees also apply regardless of unit size and can be a large share of total cost, so get quotes from your utility providers early.
The savings come from impact fees. Under Government Code Section 66311.5, ADUs with less than 750 square feet of interior livable space are exempt from most local impact fees, including park, transportation, fire facility, and library fees. Units under 500 square feet also avoid school developer fees. ADUs between 500 and 750 square feet can still be charged a per-square-foot school fee; as of early 2026, the statewide Level 1 rate is $5.38 per square foot.
Interior livable space is measured as space intended for living, sleeping, eating, cooking, or bathing, and does not include exterior wall thickness. If your design is near the 750-square-foot line, that measurement rule can keep you under the threshold.
How the Permit Process Works
Applications go through EPIC-LA, the county’s electronic permitting portal, where you create an account, upload plans, pay fees, and receive comments from both the planning and building divisions.7Los Angeles County Department of Regional Planning. EPIC-LA Your submission package needs architectural plans (site plan, floor plans, roof plan, four-sided elevations), structural plans and calculations, Title 24 energy compliance sheets, the ADU application form, and an Owner-Builder Declaration if you’re acting as your own general contractor.8Los Angeles County Department of Regional Planning. Step-by-Step Guide for Accessory Dwelling Units in the County of Los Angeles Unincorporated Areas Junior ADUs also need the Covenant and Agreement.9California Energy Commission. 2025 Energy Code Accessory Dwelling Units FAQs
State law gives the county 60 days from receipt of a complete application to approve or deny it. The review is ministerial: staff check your plans against fixed standards rather than weighing whether the neighborhood wants the unit. If your plans comply, approval is mandatory.1California Legislative Information. California Government Code – 65852.2 When the county sends back correction requests, the clock typically pauses until you resubmit, which is why mismatches between forms and plans (one of the most common correction triggers) are worth catching before submission.
Renting Your ADU
You can rent an ADU, but only on leases of 30 consecutive days or longer. California prohibits short-term rental use of ADUs, so vacation rentals, corporate housing under 30 days, and hotel-alternative platforms are off the table even if your primary home would otherwise qualify.
Adding an ADU also changes your lot’s classification. What was a single-family lot may now be treated as multi-family, since two dwelling units share a parcel that cannot be subdivided. That change can trigger rental registration and tenant protection obligations under local ordinances. The ADU itself is likely exempt from state rent caps under the Tenant Protection Act if it was built after 2010, because that law only reaches housing at least 15 years old. The existing primary residence on the same lot, however, can lose its single-family exemption from rent stabilization once a second unit exists on the parcel. Factor that in before you list.