Tiny home rules in Castro Valley, CA — covering tiny houses on wheels (THOWs), park model RVs, and tiny home on foundation builds — determine where they are legal and how they get permitted.
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.
Alameda County added Chapter 17.55 through Ordinance O-2024-32 (adopted September 19, 2024) to govern ADUs and Junior ADUs in unincorporated areas, implementing California Government Code Section 65852.2. State law preempts most local restrictions for ADUs at or under 1,200 sq ft and limits side and rear setbacks for new detached ADUs to 4 feet. JADUs are limited to 500 sq ft under Government Code Section 65852.22, are permitted only on R-1 lots with a single dwelling, and require owner occupancy. A foundation tiny home can be permitted as an ADU; California Residential Code Appendix Q sets standards for tiny houses 400 sq ft or less. A tiny house on wheels is treated by HCD as a recreational vehicle (ANSI A119.5) requiring DMV registration; the county has not published an unincorporated ordinance authorizing movable tiny houses as primary residences. Confirm any project with Planning at (510) 670-5400.
Siting a tiny house on wheels as a permanent residence without a permit can be cited as an unpermitted dwelling under Title 17 and Title 15 and may trigger removal. A foundation tiny home that exceeds Chapter 17.55 size, setback, or height standards is enforceable through county zoning.
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Side-by-side rule comparisons with other cities in Alameda County.
See how other cities in Alameda County handle tiny homes.
See how Castro Valley's tiny homes rules stack up against other locations.
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