Accessory Structures in Alameda County, CA (2026)

5 county-level rules, plus city-specific rules for 7 cities in Alameda County, California.

Verified from official government sources

Note: These county rules apply to unincorporated areas of Alameda County. If you live within an incorporated city, that city's own rules apply — see the city list below.

ADU Rules

Alameda County complies with California Government Code 65852.2 mandating ministerial ADU approval. ADUs up to 1,200 sqft for detached and JADUs up to 500 sqft are allowed on most residential lots.

ADU Rules in Alameda County

Few Restrictions

Full ordinance details →Official source ↗

Shed Rules

Unincorporated Alameda County regulates sheds under Title 17 Section 17.52.260: a detached accessory building in any R district must be one story, no taller than 15 feet, and at least 6 feet from any other building on the lot. Title 15 adopts the California Residential Code; sheds 120 sq ft or less are generally permit-exempt under CRC R105.2.

Alameda County Shed Rules

Some Restrictions

Full ordinance details →Official source ↗

Garage Conversions

Converting an attached or detached garage to an ADU in Alameda County is allowed ministerially under CA Gov Code 65852.2, with no replacement parking required for the ADU conversion.

Garage Conversion Rules in Alameda County

Few Restrictions

Full ordinance details →Official source ↗

Carport Rules

Carports in Alameda County generally require a building permit and must meet residential setbacks. They may count toward lot coverage limits but are often allowed in setbacks with reduced requirements.

Carport Rules in Alameda County

Some Restrictions

Full ordinance details →Official source ↗

Tiny Homes

Unincorporated Alameda County treats a foundation tiny home as an Accessory Dwelling Unit under Title 17 Chapter 17.55 (Ordinance O-2024-32, Sept 2024). ADUs up to 1,200 sq ft are generally by-right under California Government Code Section 65852.2. A tiny house on wheels is classified by HCD as a recreational vehicle under ANSI A119.5 and is not a permanent dwelling.