Garage conversion in San Jose: turn your garage into a legal ADU

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.

Who this is for

• You have a garage you use for storage, not parking, and want a legal living unit.
• You want one fixed price in writing for the defined scope, with permits included in the plan.

Garage already converted without a permit? That is a different job. Start here.

What the conversion includes

A real conversion is more than drywall and a new door.

• Insulation in the walls, ceiling and floor, to code.
• Framing and interior finish.
• New or larger windows for light and legal egress.
• Plumbing and electrical for a kitchen and bath.
• Heating and ventilation that meets Title 24.
• The garage door replaced with a wall, window or entry that matches the house.
• City of San José permits, and the inspections.

How the job runs

1. Walk the property.We look at the garage and tell you what is possible.
2. Price in writing.You get a fixed price in writing for the defined scope.
3. Permits.We pull the City of San José permits, Title 24 energy paperwork included.
4. Build.Insulation, framing, windows, plumbing and electrical go in, and the garage door becomes a wall, window or entry that looks like it was always part of the house.
5. Inspections.We meet the inspectors and close out the permit.

What a garage conversion costs in San Jose

Published Bay Area estimates vary widely. GreatBuildz puts a garage conversion to a legal ADU with a kitchen, bathroom and separate entrance at $100,000 to $150,000. Barcci Builders gives $180 per square foot for a detached garage with good bones and up to $350 per square foot for an attached garage that needs major structural changes, with project totals from $150,000 to $400,000. 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. For comparison with building a detached ADU, 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: Barcci Builders puts San Jose garage ADU rents at about $3,000 to $4,000 per month. Because the shell already exists, conversions also tend to move faster than a detached ADU build.

What the code asks of the finished space

A garage was built to hold cars, so the conversion has to bring it up to the standard for a room people live in. These are the minimums that shape most garage conversions, from the 2025 California Residential Code:

• Ceiling height: habitable space needs a ceiling of at least 7 feet. Bathrooms and laundry rooms need at least 6 feet 8 inches.
• Escape window: every sleeping room needs an emergency escape opening of at least 5.7 square feet (5 square feet at grade floor), at least 24 inches high and 20 inches wide, with the sill no more than 44 inches above the floor.
• Smoke alarms: when permitted alterations are made, the whole home must get smoke alarms located as required for a new home.

Two rules work in your favor. When a garage is converted to an ADU, the City cannot require the lost parking spaces to be replaced, under California Government Code 66314. And the City of San José says ADUs under 750 square feet are not subject to parkland and school impact fees. The City decides what applies to your garage. Not sure whether a conversion or a new unit fits your lot? See ADU vs garage conversion in San José.

Permits and code

A garage-to-ADU conversion requires City of San José permits and Title 24 energy compliance, and homes built on or before January 1, 1994 also need SB 407 water-conserving fixtures. That reads like a lot of paperwork, but it's our paperwork, not yours. We pull the permits, meet the inspectors, and hand you a unit that is documented and inspected. See our permit guide.

Already have a garage that was converted without a permit? See how to legalize an unpermitted garage conversion in San José.

Already converted without a permit?

Many South Bay garages were converted years ago without permits, often by a previous owner. That is a different job from a new conversion: the city inspects what is already there, and you correct what fails. If the space was a living unit before January 1, 2020, state law gives you a much easier path. See our guides to legalizing an unpermitted unit as an ADU and California's ADU amnesty, and check the penalty rules by city if you are outside San Jose.

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).
• California Residential Code, 2025 edition, Chapter 3 (ceiling height, escape openings and smoke alarms).
• California Government Code 66314 (replacement parking for garage conversions).
• 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).