ADU Rules in Los Angeles: Size, Setbacks, Garage Conversions and Permits

Accessory dwelling units, or ADUs, are one of the most popular projects for homeowners in Los Angeles. Families use them for aging parents, adult children, a home office or rental income. California has passed several laws over the past few years that make ADUs easier to build, but the rules can still be confusing. This guide explains the basics in plain English.

Every property is different, so treat this as a starting point and confirm the details for your lot before you design anything.

The four types of ADUs

• Detached ADU: a separate backyard cottage or small home.

• Attached ADU: an addition connected to your main house with its own entrance.

• Conversion ADU: an existing garage, basement or other space converted into a living unit.

• Junior ADU (JADU): a unit of no more than 500 square feet created within the walls of a single-family home, such as a converted bedroom suite.

How many ADUs can I build on a single-family lot?

Under state law, a single-family lot can have at least one ADU created from existing space, one junior ADU, and one newly built detached ADU. That means many Los Angeles homeowners can add more than one unit to the same property.

How big can an ADU be?

• State law requires cities to allow an ADU of at least 800 square feet, as long as other basic standards are met.

• In the City of Los Angeles, a detached ADU can generally be up to 1,200 square feet.

• An attached ADU is generally limited to 50 percent of the main home's living area, but the 800-square-foot minimum still applies.

• A junior ADU can be up to 500 square feet.

Setbacks and height

Setbacks are the required distance between the building and your property lines.

• Side and rear setbacks: state law limits cities to requiring no more than 4 feet from the side and rear property lines for a new ADU.

• Garage conversions: converting an existing garage or other existing structure does not trigger new setback requirements.

• Height for a detached ADU: cities must allow at least 16 feet. That increases to 18 feet for lots within a half mile of major transit, with an extra 2 feet allowed to match the roof pitch of the main house.

• Height for an attached ADU: up to 25 feet or the height limit for your zone, whichever is lower.

Parking

Parking is often the biggest worry for homeowners, and state law is generous here:

• No parking can be required for an ADU within a half mile walking distance of public transit.

• If you convert or demolish a garage to build an ADU, the city cannot require you to replace those parking spaces.

Fees

ADUs under 750 square feet are exempt from impact fees under state law. Larger ADUs can be charged impact fees in proportion to the size of the ADU compared to the main home. You will still pay plan check and permit fees.

Do I have to live on the property?

For a regular ADU, no. State law no longer allows cities to require the owner to live on the property. Junior ADUs are different. A JADU that shares a bathroom or kitchen with the main home generally requires the owner to live on the property.

Permits in Los Angeles

In the City of Los Angeles, ADU permits go through the Los Angeles Department of Building and Safety (LADBS). A few things to know:

• Review timeline: under state law, once your application is complete, the city has 60 days to approve or deny it.

• Standard Plan Program: LADBS offers pre-reviewed ADU designs from architects and builders. Using a standard plan can shorten plan check because the design has already been reviewed for building code compliance.

• Utilities: LADBS requires an ADU to have its own water shut-off valve that is accessible in the unit and its own electrical panel.

• Fire sprinklers: generally only required if the main house already has fire sprinklers or if sprinklers are required because of major remodeling.

If you live in another city in the Los Angeles area, such as Glendale, Burbank or Santa Monica, your project goes through that city's building department instead. State ADU law still applies, but local details and fees vary.

Check your lot before you design

Some lots have extra requirements. Before you spend money on plans, look up your property on ZIMAS (zimas.lacity.org), the City of Los Angeles zoning map. It shows your zone and whether your lot is in a Hillside Area, a Very High Fire Hazard Severity Zone, a historic preservation zone or another special area. These can add requirements for access, fire safety or design review.

Already have an unpermitted unit?

California law also created a path for some unpermitted units built before January 1, 2020 to be legalized as ADUs. LADBS has a separate process for these projects. If you have an existing unpermitted garage conversion or guest unit, ask about this option before you tear anything down.

The bottom line

California law makes it easier than ever to add an ADU, but every lot is different. The best first step is a site visit to look at your lot, utilities, access and zoning, then a clear plan and budget before you submit for permits.

Realco Home Remodeling is a licensed general contractor (CSLB License No. 1061619) that builds ADUs, garage conversions and room additions throughout Los Angeles and the surrounding area. We handle design coordination, permits and construction under one contract. Call (818) 806-8173 or request a free estimate to talk about your property.

This article is general information based on California and City of Los Angeles rules as of 2026. Rules change and every lot is different, so confirm the requirements for your property with your local building department.

Sources

• California Department of Housing and Community Development, Accessory Dwelling Unit Handbook (March 2026), Government Code sections 66310 to 66342

• Los Angeles Department of Building and Safety, ADU program and Standard Plan Program

• Los Angeles Department of Building and Safety, Information Bulletin P/BC 2026-150