Tiny Homes: Castro Valley vs Hayward
How do tiny homes rules compare between Castro Valley, CA and Hayward, CA?
Castro Valley and Hayward have similar restriction levels.
Castro Valley, CA
Alameda County
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.
View full Castro Valley rules →Hayward, CA
Alameda County
Hayward allows tiny homes as ADUs on foundations. Tiny homes on wheels are restricted; Movable Tiny Houses are allowed as JADU equivalents in some cases.
View full Hayward rules →Key Facts Comparison
| Fact | Castro Valley | Hayward |
|---|---|---|
| Authority | Title 17 Chapter 17.55 (Ord. O-2024-32) | - |
| ADU By-Right Size | Up to 1,200 sq ft (Cal. Gov. Code 65852.2) | - |
| JADU Max Size | 500 sq ft (R-1 only, owner-occupied) | - |
| Detached ADU Setbacks | 4 ft side/rear (state minimum) | - |
| Tiny Home on Foundation | Permitted as ADU (CRC Appendix Q for ≤400 sq ft) | - |
| Tiny House on Wheels | RV per HCD; ANSI A119.5; not a dwelling unit | - |
| ADU Amnesty Law | AB 2533 (Cal. Gov. Code 66332), eff. Jan 1, 2025 | - |
| Confirm With | Alameda County Planning (510) 670-5400 | - |
| On foundation | - | Allowed as ADU |
| On wheels | - | Not as permanent home |
| RV parks | - | Only licensed stays |
| HCD modular | - | Allowed as ADU |
| Review | - | 60-day ministerial |
Highlighted rows indicate differences between cities.
Castro Valley FAQ
Can I put a tiny house on wheels in my backyard in unincorporated Alameda County?
California HCD treats tiny houses on wheels as recreational vehicles under ANSI A119.5 standards, not as dwelling units. Alameda County has not published an unincorporated ordinance that authorizes a movable tiny house as a permanent residence the way some California cities have. Confirm with the Alameda County Planning Department at (510) 670-5400 before siting a unit.
What size ADU does Alameda County allow on an unincorporated lot?
Chapter 17.55 of Title 17, adopted by Ordinance O-2024-32, implements California Government Code Section 65852.2. ADUs up to 1,200 square feet are generally available by-right, with a 4-foot side and rear setback minimum for new detached units. Junior ADUs are limited to 500 square feet under Government Code Section 65852.22 and require an owner-occupied R-1 lot.
Does Alameda County allow a tiny house on a permanent foundation?
Yes, when permitted as an Accessory Dwelling Unit under Chapter 17.55. A small foundation-based tiny home of 400 square feet or less can be designed under California Residential Code Appendix Q, which sets specific lofts, ladders, and ceiling-height standards for tiny houses. The unit must still meet ADU setbacks, height, and design standards under Chapter 17.55.
Hayward FAQ
Can I live in my RV in my driveway?
No. Hayward prohibits full-time residency in RVs on private residential property.
Is a park model OK as an ADU?
Only if HCD-certified and installed on a permanent foundation with full ADU permits.
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