Garage Conversions: El Cerrito vs Martinez
How do garage conversions rules compare between El Cerrito, CA and Martinez, CA?
Martinez has fewer restrictions than El Cerrito.
El Cerrito, CA
Contra Costa County
Attached and detached garages in unincorporated Contra Costa must meet zoning setbacks and building code fire separation (1/2-inch gypsum from dwelling). Garages cannot be converted to living space without a permit, though garage-to-ADU conversions are streamlined under state law with no replacement parking near transit.
View full El Cerrito rules →Martinez, CA
Contra Costa County
Martinez regulates ADU and JADU development under Martinez Municipal Code Chapter 22.43, consistent with California Government Code §65852.2. Garage conversions are by-right with no replacement parking required, no minimum lot size, and existing garage setbacks preserved for the conversion footprint.
View full Martinez rules →Key Facts Comparison
| Fact | El Cerrito | Martinez |
|---|---|---|
| Fire separation | 1/2 in gypsum + 20-min self-closing door | - |
| Setback (detached) | 3 ft side/rear typical R-zones | - |
| Conversion to living | Requires permit + full CRC compliance | - |
| Garage-to-ADU parking | No replacement required near transit | - |
| Commercial use | Triggers home-occupation review | - |
| Code | - | Martinez MC Ch. 22.43 |
| Replacement Parking | - | Not required |
| Existing Setbacks | - | Preserved for conversion |
| JADU Cap | - | 500 sq ft |
| Review Timeline | - | 60-day ministerial |
Highlighted rows indicate differences between cities.
El Cerrito FAQ
Can I convert my garage to a bedroom without a permit?
No. Converting a garage to any habitable use requires a building permit, plan review, and final inspection. Unpermitted work creates liability at sale and can trigger enforcement.
Do I need replacement parking when I convert to an ADU?
No, if the site qualifies under AB 68—within a half mile of transit, in a historic district, or for a JADU or a converted ADU.
Martinez FAQ
Do I need to replace parking if I convert my Martinez garage to an ADU?
No. Cal. Gov Code §65852.2 and Martinez Municipal Code Chapter 22.43 prohibit the City from requiring replacement parking when an existing garage is converted to an ADU.
How big can my Martinez garage-conversion ADU be?
The City must allow up to 800 sq ft for any ADU under §22.43, and up to 1,200 sq ft for a detached or 2-bedroom attached ADU. JADUs in attached garages are capped at 500 sq ft within the primary dwelling.
Who processes a Martinez ADU permit?
Martinez Planning Division handles the ministerial zoning review under §22.43 (60-day timeline), and the Martinez Building Division issues the building permit under the California Residential Code.
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