A garage conversion is usually the lowest-cost path to an ADU in San Jose — $100,000-$220,000, versus $180,000-$400,000 for a new detached build — because the shell already exists.
Garage Conversion Cost in San Jose
Converting an existing garage in San Jose runs $100,000-$220,000. That's well under the $180,000-$400,000 typical cost of a ground-up detached ADU, because you're reusing the foundation, walls, and roof. The biggest variables are whether the slab and framing are sound, what utility/electrical upgrades are needed, and your finish level. Permit fees add $4,000-$14,000. A converted unit rents for about $2,000-$2,800/mo (1BR) in San Jose.
The San Jose Garage Conversion Permit Process
A garage-to-ADU conversion in San Jose needs building permits even if the exterior is unchanged. Approval process: Ministerial review The review timeline is 60 days, with plan check: Standard review process. Pre-approved plans: Limited pre-approved options available.
- Confirm eligibility — ADUs are allowed in All residential zones (R-1, R-2, R-M, R-MH).
- Prepare conversion plans — layout, egress windows, insulation, ventilation, smoke/CO detectors, plus a kitchen and bathroom.
- Submit for plan check — Standard review process.
- Pull permits and build — fees run $4,000-$14,000; then framing, electrical, plumbing, and final inspection.
No Replacement Parking Required
No. California law (AB 68 / Gov Code §66314) prohibits cities from requiring replacement parking when you convert or demolish a garage to build an ADU — so you do not need to add a parking space anywhere on the lot. Owner-occupancy is not required, so you can rent the converted unit out.
The JADU Option for an Attached Garage
If your garage is attached to the house, you can convert it into a junior ADU (JADU) — capped at 500 sq ft and built within the existing walls. JADUs are cheaper and faster to permit than a full ADU, though they may share sanitation with the main home. A full ADU gives you more size and a separate unit; a JADU is the budget route.
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San Jose Garage Conversion FAQ
How much does a garage conversion cost in San Jose?
Do I need a permit to convert a garage in San Jose?
Do I have to replace the parking if I convert my garage in San Jose?
How long does a garage conversion take in San Jose?
Can I convert an attached garage into a JADU in San Jose?
Compare your options: see the full San Jose ADU rules, estimate your build with the San Jose ADU cost calculator, or read the general garage conversion guide.