Planning

California ADU laws, what’s changed.

State law has made building an ADU meaningfully easier over the past few years, with several more changes landing in 2026. Here’s what actually affects a homeowner planning one, in plain terms.

What’s changed

• You no longer have to live on the property. The owner-occupancy requirement for ADUs has been permanently eliminated statewide — a meaningful change for anyone considering an ADU purely as a rental.
• Junior ADUs got the same treatment, with one condition. The owner-occupancy requirement is also eliminated for JADUs that don’t share a bathroom with the main house.
• Size limits now count differently. Maximum ADU and JADU size is based on interior livable space only — wall thickness no longer eats into your allowed square footage.
• Smaller ADUs are exempt from school impact fees. Units under 500 square feet don’t get hit with this cost, which can otherwise add meaningfully to a small project’s budget.
• Cities have to act fast, or your project is automatically approved. Local agencies work under a ministerial approval process with a firm decision window — if a city sits on a complete application past the deadline, it’s treated as approved.

Where it gets complicated

Cities are still catching up their own local codes to match these state changes, and enforcement varies — the state’s housing department has been actively sending ordinance-correction letters to cities whose local rules haven’t been updated yet. And in areas affected by the 2025 wildfires, a state executive order allows local agencies in Los Angeles County to restrict certain lot-split projects in high fire-hazard areas during post-fire rebuilding. Practically: the state rules set the floor, but your specific city’s current ordinance is what actually governs your project, and it’s worth confirming directly with your local planning department rather than assuming the statewide rule applies exactly as written.

Based on 2026 legal-update sources and state housing department bulletins; this is general information, not legal advice, and some effective dates and bill numbers conflict across sources. Confirm current requirements with your city’s planning department or the California Department of Housing and Community Development (hcd.ca.gov) before relying on anything here for a real project.

See our ADU cost guide and ADU rental income guide for the financial side of the decision.