A garage conversion is usually the lowest-cost path to an ADU in San Jose — $90,000-$150,000, versus $200,000-$450,000 for a new detached build — because the shell already exists.
Garage Conversion Cost in San Jose
Converting an existing garage in San Jose runs $90,000-$150,000. That's well under the $200,000-$450,000 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 FY 2026-27 Building Fee Schedule (effective Aug 10, 2026): ADU 0-750 sq ft $422 issuance + $1,137 plan review + $1,732 inspection = $3,291; 751-1,200 sq ft $633 + $1,950 + $2,520 = $5,103. Excludes construction taxes, school and parkland fees and any planner meeting ($398/hour).. A converted unit rents for about $2,500-$3,000/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 building permit, no planning hearing. Step 1: complete the ADU Universal Checklist (Bulletin #210) and, optionally, book a preliminary virtual meeting with a planner ($398/hour, 30-minute minimum). Step 2: prepare plans to Bulletin #211. Step 3: open the application on SJPermits.org (folder '1 & 2 Family Detached Dwellings (including ADU)', sub-type 'ADU') and name an ePlan Applicant. Step 4: upload to SJePlans the plans, Bulletin #213 inspection checklist, Title 24 energy and CALGreen documents, Form 302 address request, Form 312 owner declaration (Form 313 deed restriction for a JADU), and the water company's hydrant flow letter. Step 5: Prescreen, Plan Review and Issuance Review in SJePlans. Step 6: construction, inspections and final. Multifamily lots and AB 2533 legalizations go through the ADU Ally team (adu.ally@sanjoseca.gov); preapproved plans use a separate expedited path. The review timeline is City-published: the first round of building review typically takes 20 business days and complete plans stay within one or two cycles (ADU FAQs); preapproved plans can be issued the same day as the review meeting. Gov. Code 66317 (SB 543) deems the application approved after 60 days., with plan check: Electronic review in SJePlans in three phases: Prescreen (a permit specialist confirms the package is complete and invoices the initial plan review fee), Plan Review (comment and resubmittal cycles, all through SJePlans), and Issuance Review (residual plan review and inspection fees, taxes, school and parkland fees paid, then the permit card and stamped plans are released). Fire Prevention checks a 150 ft hose path along a 4 ft clear route, a hydrant within 600 ft and a 1,000 gpm at 20 psi flow letter from the water company; the missing letter is the city's most-cited cause of delay.. Pre-approved plans: Yes. The Preapproved ADU program currently lists 7 city-reviewed standard plans from 5 vendors, 476-799 sq ft (1 bed/1 bath to 2 bed/2 bath); about 15 further plans from 7 vendors, 440-1,000 sq ft, are under review and not yet eligible. Applicants still submit a site-specific plan (siting, setbacks, utilities); a dedicated review team can issue the permit the same day as the plan review meeting when the site documents are complete (deferred structural submittals, clearances or variances take longer). Eligibility: a residential lot with an existing single-family home or duplex, outside geohazard, landslide, flood and Wildland-Urban Interface zones. Gov. Code 65852.27 governs pre-approved plan programs..
- Confirm eligibility — ADUs are allowed in Any zoning district where the lot has a legally permitted single-family, duplex or multifamily dwelling (SJMC 20.80.175 A; ADU Universal Checklist, Bulletin #210 rev. Sept 16, 2026, Part 1). An open Code Enforcement case must be closed before plans are accepted. Flood zones A/AE/AH/AO, geohazard, landslide or liquefaction zones, Historic Resources Inventory listing and Wildland-Urban Interface areas add design rules or clearances rather than prohibiting the unit..
- Prepare conversion plans — layout, egress windows, insulation, ventilation, smoke/CO detectors, plus a kitchen and bathroom.
- Submit for plan check — Electronic review in SJePlans in three phases: Prescreen (a permit specialist confirms the package is complete and invoices the initial plan review fee), Plan Review (comment and resubmittal cycles, all through SJePlans), and Issuance Review (residual plan review and inspection fees, taxes, school and parkland fees paid, then the permit card and stamped plans are released). Fire Prevention checks a 150 ft hose path along a 4 ft clear route, a hydrant within 600 ft and a 1,000 gpm at 20 psi flow letter from the water company; the missing letter is the city's most-cited cause of delay..
- Pull permits and build — fees run FY 2026-27 Building Fee Schedule (effective Aug 10, 2026): ADU 0-750 sq ft $422 issuance + $1,137 plan review + $1,732 inspection = $3,291; 751-1,200 sq ft $633 + $1,950 + $2,520 = $5,103. Excludes construction taxes, school and parkland fees and any planner meeting ($398/hour).; 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 maximum, 150 sq ft minimum, inside the walls of an existing or proposed single-family home (an attached garage counts). Since Ordinance 31329 (effective July 16, 2026) SJMC 20.80.178 applies Gov. Code 66333 directly: an efficiency kitchen is required, the bathroom may be shared, rentals must be 30 days or longer, and a deed restriction (Form 313, wet-signed for the County Recorder) is recorded. One JADU plus one ADU is allowed per single-family lot (20.80.175 B.1). 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.