LA & OC ADU Permitting: A Homeowner's Overview
ADU rules in Southern California come from two directions at once: statewide laws that set a baseline, and the city or county that actually reviews your project. This overview explains how those fit together in Los Angeles and Orange County and points you to the official sources — the only places to confirm current detail. We deliberately avoid quoting specific numbers, because they vary and change.
State sets the floor; your jurisdiction runs the review
California has adopted a series of laws intended to make accessory dwelling units easier to build, and local agencies generally cannot go below the baseline those laws establish. Within that baseline, each city and county applies its own standards and runs its own permit review. So two things are always true at once: state law matters, and the specifics for your address are set and enforced locally. The California Department of Housing and Community Development maintains the statewide reference at its ADU information page.
Who reviews your ADU in Los Angeles
It depends on whether your property is inside the City of Los Angeles or in another city or an unincorporated area:
- City of Los Angeles. Planning matters go through LA City Planning, and building permits and plan-check go through the Department of Building and Safety, LADBS.
- Unincorporated Los Angeles County. Planning is handled by LA County Planning, with building and safety under LA County Public Works.
- Other cities in LA County. Each incorporated city (Pasadena, Santa Monica, Burbank, and so on) runs its own planning and building departments with their own counters and processes.
Who reviews your ADU in Orange County
Orange County is largely made up of incorporated cities, so for most addresses the relevant authority is your city's planning and building department — Anaheim, Irvine, Santa Ana, Huntington Beach, and the rest each handle their own permits. For unincorporated parts of the county, building and development services are provided through OC Public Works. The practical first step is always to identify exactly which jurisdiction your parcel sits in.
About "pre-approved" ADU programs
You may see references to pre-approved or pre-reviewed ADU plan programs, in which a local agency reviews certain standard plans in advance. Where these exist they are specific to the jurisdiction, and whether one applies to your address and a given plan is a question for that agency. Treat a "pre-approved" label with the same question we use everywhere: pre-approved by whom, for what, and does it apply here? Our piece on what pre-approved plans are unpacks the term.
Extra layers that can apply
Beyond the base ADU review, hillside areas, fire hazard zones, historic districts, coastal zones, and HOAs can each add requirements or steps. These do not necessarily rule out an ADU, but they change what is feasible and can affect timing — see historic overlays and zoning limits and hillside-lot considerations.
How to use this
Start by confirming your jurisdiction, then read that agency's current ADU guidance and ask what they require and how review is running now. We cover why we don't promise a timeline in how long permits take with ready-made plans, and you can see local context for each region on our service-areas pages.
State law sets the floor. Your city or county sets the detail. The only reliable answer is the one from the agency that reviews your address.
Kevin Cohen Design works on ADUs across Los Angeles, Orange County, and beyond — from ready-made ADU plans to custom ADU design and build, including help with permits and plan-check.
General information only, not legal, engineering or code advice. Links are to official agencies whose information and processes change over time; always confirm the current rules and requirements for your specific property with the jurisdiction that reviews it.