Garage conversion in San Jose
Turning a garage into a legal ADU is the most affordable way to add a rentable unit. Here's what it costs in San Jose in 2026 (with sources), what's involved, and how permits work.
A garage conversion is often the smartest first move for San Jose homeowners who want an ADU without the cost of building from the ground up. The structure is already there — foundation, walls, and roof — so the project focuses on making the space 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–$225,000, or roughly $180–$350 per square foot. The low end reflects a sound detached garage that needs mainly insulation, finishes, and a kitchen and bath; the high end reflects attached garages that need structural changes, new utilities, or premium finishes. A junior ADU (JADU) garage conversion with a shared bath can start lower — around $30,000–$80,000. By comparison, a detached ADU usually runs well into the $200,000s; see our ADU cost guide.
Why convert a garage
It's typically the lowest-cost path to a legal ADU, it uses space many households rarely use for parking, and it can generate rental income — San Jose garage ADUs commonly rent for about $2,600–$4,000 per month. Because the shell already exists, conversions usually move faster than a detached ADU build.
What's involved
A proper conversion is more than drywall and a door. We insulate walls, ceiling, and floor to code; frame and finish interior walls; add or enlarge windows for light and 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 original to the home.
Permits and code
Garage-to-ADU conversions require City of San José permits, Title 24 energy compliance, and SB 407 water-fixture updates — and California's ADU-friendly rules have made approvals more straightforward than they used to be. We handle the full permit process and inspections so the unit is 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/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.