California ADU Rules in 2026: Size, Setbacks & Parking

California has the most homeowner-friendly ADU law in the country, codified at Government Code §66314 and following. It preempts local bans, so even if your city's old zoning code says no, the state rules generally win. Here's what actually applies in 2026.

Size: the 800 sq ft guarantee

Your city must allow a detached ADU of at least 800 sq ft regardless of lot coverage, floor-area-ratio or other local limits. Most cities allow up to 1,200 sq ft. A junior ADU (JADU) is capped at 500 sq ft and must be inside the existing home.

Setbacks: 4 feet

The maximum side and rear setback a city can require is 4 feet. Converting an existing structure (like a garage) requires no additional setback at all, even if it sits on the property line.

Parking: often none

No replacement or additional parking can be required if the ADU is within half a mile walking distance of public transit, in a historic district, or part of the existing or proposed primary residence. In practice, a large share of California lots qualify for zero added parking.

Owner-occupancy: no longer required

Thanks to AB 976, the owner-occupancy requirement is permanently barred for ADUs. You can rent out both the main house and the ADU without living on the property — a major change for investors.

Approval: 60 days, ministerial

A complete ADU application must be approved or denied within 60 days, ministerially — meaning no public hearing and no discretionary design review. ADUs under 750 sq ft are also exempt from impact fees.