Garage conversion in San Jose
Your garage already has the expensive parts: a foundation, walls, and a roof. That head start makes converting it the most affordable way to add a rentable unit. Here's what it costs in San Jose in 2026 (with sources), what the work involves, and how permits play out.
Most San Jose garages hold boxes, not cars. Converting one is often the smartest first move for homeowners who want an ADU without paying to build from bare dirt. The structure is already standing, so the project isn't about erecting a building. It's about turning space you already own into a home that's livable, efficient, and fully up to code.
What a garage conversion costs in San Jose
As of 2026, a fully permitted garage conversion in San Jose commonly runs about $80,000–$200,000, or roughly $180–$350 per square foot. What moves the number is the garage you're starting with. A sound detached garage that mostly needs insulation, finishes, and a kitchen and bath lands near the low end; an attached garage that needs structural changes, new utilities, or premium finishes climbs toward the top. A junior ADU (JADU) garage conversion with a shared bath can start lower, around $50,000–$90,000. For comparison, a detached ADU usually runs well into the $200,000s; see our ADU cost guide.
Why convert a garage
Three reasons come up on almost every walkthrough. It's typically the lowest-cost path to a legal ADU. It reclaims space most households use for storage rather than parking. And it can earn its keep: San Jose garage ADUs commonly rent for about $2,600–$4,000 per month. Because the shell already exists, conversions also tend to move faster than a detached ADU build.
What the work actually involves
A real conversion is more than drywall and a new door. We insulate walls, ceiling, and floor to code; frame and finish the interior; add or enlarge windows so the space gets genuine light and legal egress; run plumbing and electrical for a kitchen and bath; install heating and ventilation that meets Title 24; and replace the garage door with a wall, window, or entry that looks like it was always part of the house.
Permits and code
A garage-to-ADU conversion requires City of San José permits, Title 24 energy compliance, and SB 407 water-fixture updates. That reads like a lot of paperwork, but California's ADU-friendly rules have made approvals more straightforward than they used to be, and it's our paperwork, not yours. We pull the permits, meet the inspectors, and hand you a unit that's legal, safe, and properly documented. See our permit guide.
Sources
Figures are 2026 planning ranges for the San Jose area and vary by project, lot, and finish level; they are not quotes. Compiled from the sources below; the only way to know your number is a free, lot-specific estimate.
- City of San José: Accessory Dwelling Units (ADU and garage-conversion permits and requirements).
- GreatBuildz: Garage Conversion Costs in the Bay Area (cost ranges and per-square-foot data).
- Garage Conversion ADU Cost, Bay Area (Silicon Valley conversion pricing).