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ADU Rules in Los Angeles.

Plain-English information about the rules that shape ADUs, JADUs and garage conversions in Los Angeles County.

Photo: Accessory Dwelling Unit by Sightline Institute, CC BY 2.0, via Openverse (flickr).

Last reviewed 2 min read

Rules for ADUs come from state law, your city or county, and your lot. This section explains how those pieces fit together in plain language.

What this topic covers

California's ADU law sits in Gov. Code sections 66310 to 66342. It was renumbered in 2024 (SB 477, effective March 25, 2024) from the former section 65852.2. Cities and counties must follow it, and they can add local rules only above the state floor.

Key facts

  • Section 66323(a) lists ADUs a city "shall ministerially approve," including one detached ADU with side and rear setbacks of no more than four feet.
  • Section 66317 gives the agency 60 days to act on a complete application.
  • A local ordinance may cap a detached ADU, but not below 850 square feet (studio or 1 bedroom) or 1,000 square feet (2 or more bedrooms), per ABAG's July 2025 summary. The 1,200 square foot figure applies only where a city has no ADU ordinance.
  • Section 66314(a) limits when a city can bar ADUs in fire zones to findings about traffic flow and public safety.
  • HCD's 2024 review found 17 places where the City of Los Angeles ordinance did not match state law, and state law controls where they conflict.

Guides in this hub

Before you start

  • Confirm which agency permits your address: City of Los Angeles, unincorporated LA County, or another city.
  • Check your lot against the state minimums: 800 square feet, four-foot setbacks and 16 feet of height.
  • Look up your fire zone and whether the lot is in a hillside area.
  • Ask the agency in writing which code sections it relies on, since older ordinances still cite the deleted section numbers.

How the pieces fit

State law sets what a city must allow. The City of Los Angeles ordinance (No. 186481, effective December 19, 2019) and the LA County code add local detail. SB 9 is a separate law that lets owners of many single-family lots build two homes or split the lot, and it counts ADUs and JADUs toward its limit of two units per lot.

Rules change and differ from place to place. Confirm the current requirements with your city or LA County before you build.

Guides in this section.