ADUs in the East Bay: Rules by City & County

The East Bay — from Oakland and Berkeley out to Walnut Creek and beyond — has some of the strongest ADU demand in the region, with deep lots and high rents. But “the East Bay” spans two counties and dozens of cities, and the ADU rules in the East Bay depend entirely on which one you’re in. Here’s how to get oriented. (For the statewide baseline, see our Bay Area ADU guide.)

First, find your jurisdiction

Each county regulates only its unincorporated areas; if you’re inside a city, that city’s ordinance applies. Alameda County publishes a helpful per-jurisdiction lookup at the Alameda County ADU Resource Center, and Contra Costa County’s planning department posts its own standards.

Alameda County & its cities

  • Unincorporated Alameda County: Updated its ADU ordinance in 2024 to match state law (a single-family lot can generally add one ADU plus one JADU, with 4-ft setbacks). The state flagged a few provisions for amendment in 2025, so confirm the current rules before applying.
  • Oakland: ADUs up to 850 sq ft (1-bedroom) or 1,000 sq ft (2-bedroom), 4-ft setbacks for detached units, and no owner-occupancy requirement on newer ADUs.
  • Berkeley: Stricter than most — one ADU per lot, capped at 750 sq ft or 75% of the main home (whichever is less), 4-ft setbacks, and an owner-occupancy requirement with a deed restriction barring selling the ADU separately.
  • Albany, Alameda, San Leandro, Hayward, Fremont and others each have their own ordinances built on the state minimums — check the specific city.

Contra Costa County & its cities

  • Unincorporated Contra Costa County: A detached ADU up to 800 sq ft and 16 ft tall gets streamlined processing with no parking required; larger ADUs are allowed too. Setbacks are 4 ft from side and rear lines, and parking is capped at one space per bedroom (waived within a half-mile of transit).
  • Walnut Creek, Concord, Richmond, Antioch, Orinda, Lafayette and the rest each set their own standards on top of the state baseline — verify with that city’s planning department.

This page is general information, not legal or construction advice, and rules change. Confirm specifics with your city or county before you build. We’re always happy to refer trusted ADU architects and contractors who work across the East Bay — just ask.

Thinking about an ADU in the East Bay?

We’ll help you confirm your city’s rules, weigh the cost, and understand the value an ADU adds. Start with a free home valuation or call (415) 407-5324. See also: ADUs in San Francisco, Marin County, and San Mateo County. — Beatrice Kopilenko, REALTOR® · DRE #01970797 · Primavera Realty