ADU Rules: Castro Valley vs Sunol
How do adu rules rules compare between Castro Valley, CA and Sunol, CA?
Castro Valley and Sunol have similar restriction levels.
Castro Valley, CA
Alameda County
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.
View full Castro Valley rules →Sunol, CA
Alameda County
Sunol is an unincorporated CDP in Alameda County governed by Alameda County Code Title 17 (Zoning), specifically the new Chapter 17.55 (Accessory Dwelling Unit and Junior Accessory Dwelling Unit Ordinance) adopted by Ordinance O-2024-XX in 2024. The County allows one ADU plus one JADU on single-family lots in all residential zones with no minimum lot size, consistent with California Government Code §65852.2.
View full Sunol rules →Key Facts Comparison
| Fact | Castro Valley | Sunol |
|---|---|---|
| State law | Gov Code 65852.2 | - |
| Detached ADU max | 1,200 sqft | - |
| JADU max | 500 sqft | - |
| Side/rear setback | 4 feet | - |
| Review time | 60 days ministerial | - |
| Governing Code | - | Alameda Co. Code Ch. 17.55 |
| Adopted | - | Ord. O-2024-XX (2024) |
| Max Detached ADU | - | 1,200 sq ft |
| Min Lot Size | - | None |
| Septic/Well | - | Alameda Co. EH review required |
Highlighted rows indicate differences between cities.
Castro Valley FAQ
Do I need a public hearing?
No, ADUs are approved ministerially by county staff under state law; no planning commission or neighbor notice is required if the application meets objective standards.
Can I sell my ADU separately?
AB 1033 (2023) allows separate sale as condominium only if Alameda County opts in by local ordinance; check current county policy.
Sunol FAQ
Who regulates ADUs in Sunol?
Sunol is unincorporated, so the Alameda County Community Development Agency regulates ADUs under Alameda County Code Title 17, Chapter 17.55, adopted in 2024 to implement California Government Code §65852.2.
Is there a minimum lot size for a Sunol ADU?
No. Chapter 17.55 of the Alameda County Code (adopted 2024) eliminated the minimum lot size for ADUs in the unincorporated areas, consistent with state ADU law.
Do I need septic approval for a Sunol ADU?
Yes for parcels not on municipal sewer/water. Alameda County Environmental Health reviews septic-system capacity and well water before the building permit is issued.
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