Contra Costa County, CA Accessory Structures: Garage Conversions (2026)
Garage conversion rules in Contra Costa County, CA, sometimes called garage-to-ADU or accessory living unit conversions, govern permits, ceiling height, egress, and parking replacement.
Key Facts
- Code Chapter
- Chapter 82-24
- Setback for Existing Garage
- Not required
- Parking Replacement
- Only if required for primary dwelling
- State Override
- CA Gov. Code § 65852.2
- Permit
- Building permit always required
Summary
Contra Costa County allows an attached ADU to be created through an internal conversion of an existing garage; no setback is required for an existing garage being converted to an ADU under Chapter 82-24.
If an accessory dwelling unit is attached to a primary residence, the accessory dwelling unit must be an internal conversion of a garage or other area within the existing primary residence, or an addition to the existing primary residence. A setback is not required for an existing garage that is converted to an accessory dwelling unit.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Ordinance Code: Supplement 103).
Full Breakdown
Per Contra Costa County Ordinance Code Chapter 82-24, an ADU attached to a primary residence may be created as an internal conversion of a garage or other area within the existing primary residence, or as an addition to the existing primary residence. 2) does not require a setback for an existing garage that is converted to an ADU. , within one-half mile of public transit). When a garage, carport, or covered parking structure is demolished or converted in conjunction with construction of an ADU, the displaced parking space must be replaced only if necessary to comply with the off-street parking requirements applicable to the primary dwelling unit.
All converted garages must still meet building code requirements for habitability (ventilation, egress, fire separation, foundation) under the California Residential Code as adopted by the County.
Violations & Fines
Converting a garage to a habitable dwelling without a building permit and zoning approval is a code violation subject to enforcement under the County Ordinance Code. Unpermitted conversions can be ordered abated, required to be returned to garage use, or compelled to obtain after-the-fact permits and inspections.
Frequently Asked Questions
Can I convert my detached garage into an ADU?
Do I have to replace the parking I lose by converting my garage?
What permits do I need?
Sources & Official References
Other rules in Contra Costa County
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