California ADU Laws 2026: A Complete Homeowner's Guide
Everything California homeowners need to know about ADU regulations in 2026, from statewide rules to local permit timelines.
California has the most permissive ADU laws in the United States. Under SB 9, AB 68, and AB 881, every city is required to allow ADUs on most single-family lots, with size, setback, and parking minimums set at the state level.
This guide walks through what every California homeowner should know before starting an ADU project: the statewide rules that override local ordinances, the maximum size you can build, when owner-occupancy is required, and how long permits typically take in major cities.
Detached ADUs can be up to 1,200 square feet. Attached ADUs are limited to 50% of the primary residence or 800 square feet, whichever is greater. Cities must approve or deny ADU applications within 60 days of receiving a complete application.
Most cities have additional local rules layered on top of state law — height limits, design standards, and impact fees vary widely. We'll be adding city-specific permit guides for every major California market.