An accessory dwelling unit, or ADU, is a second home on your property. Families build them for aging parents, grown kids, rental income, or a home office. California has made ADUs much easier to permit over the last several years, and Los Angeles builds more of them than almost any city in the country. Here is what to know before you start.
The main types of ADUs
- Detached ADU. A separate small house in the backyard. The most flexible option and usually the most private.
- Garage conversion. Turning an existing garage into living space. Often the fastest and most affordable path because the structure already exists.
- Attached ADU. An addition connected to the main house with its own entrance, kitchen, and bathroom.
- Junior ADU (JADU). A unit of up to 500 square feet created inside the existing home, such as a converted bedroom suite with its own entrance and a small kitchen.
Key California rules that help homeowners
State law sets minimum standards that cities must follow. As of the state housing department's 2026 guidance:
- Cities generally cannot require side and rear setbacks greater than four feet for a new ADU.
- Detached ADUs are allowed at least 16 feet in height, and more on lots near major transit.
- Owner occupancy is not required for an ADU. A JADU that shares a bathroom with the main house does require the owner to live on the property.
- ADUs of 750 square feet or less are exempt from impact fees.
- Once an application is complete, the city must approve or deny it within 60 days when there is an existing home on the lot.
Rules change often, and some lots have special conditions such as hillsides, fire zones, or easements. Always confirm the current requirements for your specific property before you design.
Los Angeles has pre approved ADU plans
The Los Angeles Department of Building and Safety runs a Standard Plan Program with ADU designs that are already approved for code compliance. Using one can shorten plan check, although the city still reviews site specific items such as zoning and the foundation.
How an ADU project usually runs
- Site visit and feasibility. Look at the lot, utilities, access, and what size and type will fit.
- Design. Custom plans or a pre approved standard plan, plus structural engineering.
- Plan check and permits. The city reviews the plans and issues permits.
- Construction. Foundation, framing, utilities, insulation, drywall, and finishes, with city inspections at each stage.
- Final inspection. The city signs off and the unit is ready to live in.
Costs to plan for beyond construction
- Design and engineering fees
- Permit and plan check fees
- Utility work, including possible sewer, water, or electrical panel upgrades
- Site work such as grading, drainage, and access paths
Utility upgrades are the most common surprise on ADU projects, so check the electrical panel and sewer connection early.
Common questions
Can I rent out my ADU?
Yes. California does not require owner occupancy for ADUs, and many homeowners rent them long term. Short term rentals may be restricted by local rules.
How long does it take to build an ADU?
It depends on the type, design, and permit timeline. Garage conversions are usually the fastest. A detached ADU takes longer because it includes a new foundation and full utilities.
Do I need a separate address or utility meters?
Not always. Many ADUs share utilities with the main house. Separate meters are possible but add cost, so it is worth deciding early based on how you plan to use the unit.
This guide is general information for homeowners. Every house is different, so an on site evaluation is the only way to know what your home needs.