Garage conversion cost in San Diego and California (2026)

Garage conversion cost in San Diego

Builders publish ranges, not quotes, but the ranges cluster. Lars Remodel's 2026 San Diego cost guide puts a full design-build garage conversion at about $150,000 to $225,000+, and says slab, utility and access conditions drive the final number. Snap ADU puts the average at roughly $120,000+ to convert a two-car garage, and says actual costs vary with the garage's condition and location.

Maxable's starting figure covers design, permitting and construction for a basic unit. It also describes two 450 sq ft attached garage conversions in Southern California that came in at $160,000 and $240,000, the gap driven largely by finishes and add-ons.

Garage conversion cost per square foot

Few builders quote conversions per square foot, because so much of the cost is fixed: one kitchen, one bathroom, one set of plans, one permit. As a rough check, Maxable's two 450 sq ft examples work out to about $356 and $533 per square foot. A new detached unit in Snap ADU's March 2026 price list runs about $600 per square foot at 500 sq ft. For the broader picture, see what an ADU costs in San Diego and our ADU construction cost per square foot guide.

Cost to convert a garage: bedroom vs. ADU

The single biggest cost decision is what the garage becomes. A bedroom, office or gym stays part of your house: no kitchen, usually no new bathroom. An ADU is a second home, with its own kitchen, bathroom and entrance. The rules for each are in our guide to converting a garage to living space.

Source: This Old House's cost guide, updated June 2026. These are national averages. The ADU line is far below what San Diego builders publish, because a California ADU carries costs a simple room doesn't: a full kitchen, a bathroom with drain lines cut through the slab, an energy report, architectural and structural plans, and a separate entrance. Use the national room figures as a floor and get local bids.

One-car vs. two-car garage conversion cost

A single-car garage is about 200 to 240 square feet and a two-car garage about 400 to 440, according to This Old House. The published San Diego figures above are mostly for two-car garages; we found no builder that publishes a separate one-car price. A one-car conversion isn't half the price, because the kitchen, bathroom, plans and permit cost about the same at either size.

An attached one-car garage may fit a junior ADU instead: up to 500 square feet inside the house, with an efficiency kitchen, and it may share a bathroom with the house. Lars Remodel prices a San Diego JADU at $120,000 to $200,000+.

What goes into the cost of a garage conversion

A garage was built for cars. Every gap between a garage and a home shows up as a line in the bid. Lars Remodel lists the cost burden as kitchen, bath, insulation, egress, mechanical and electrical, and the main risk as existing conditions and code upgrades. National figures below come from This Old House (June 2026) and are for room conversions; ADU work in California usually costs more.

Slab and moisture

Many garage slabs were poured without a vapor barrier and need one under living space. Snap ADU notes that inspections often find footings not sufficient for an ADU, requiring retrofit footings at minimum, and that even when the slab is kept, all in-slab plumbing still has to be installed. Garages 30 or more years old, it says, are usually poor candidates for conversion.

Windows and egress

The garage door opening usually becomes a wall with windows and an entry door. Any bedroom needs an emergency escape opening: under the 2025 code, at least 5.7 square feet of net clear opening (5 at grade), at least 24 inches high and 20 wide, with the sill no more than 44 inches above the floor.

Heating, cooling and the energy code

The California Energy Commission treats a garage conversion as an addition, because unconditioned space becomes conditioned, so it must meet the addition rules in Section 150.2(a). The same FAQ says the Mechanical Code doesn't allow return air from an existing forced-air system to be discharged into another dwelling unit, so an attached ADU conversion generally can't share the house's ducted system. Budget for its own system, such as a mini-split. Lars Remodel notes that the solar requirement for new homes doesn't apply to a conversion of existing space.

Utilities

A city can't require a new or separate utility connection for an ADU converted from existing space, so sharing the house's water, sewer and power is allowed. If you want a separate electric meter anyway for rental billing, Snap ADU prices it at about $10,500. The electrical system itself, Snap ADU says, will likely need rerunning, and often an upgrade, to carry a kitchen and its own heating.

Permits and fees for a garage conversion

Fees are where a San Diego conversion saves real money compared with a large new ADU.

• City permit fees. Snap ADU's February 2026 table puts City of San Diego fees at about $10,734 for a 499 sq ft ADU and $25,138 at 749 sq ft. Those are a builder's figures, not an official fee schedule.
• Impact fees. San Diego exempts the first two ADUs on a property from development impact fees, whatever their size. Statewide, no impact fees apply to an ADU of 750 sq ft or less.
• School fees. None under 500 sq ft. Above that, San Diego Unified charges $5.38 per square foot.
• Sprinklers. An ADU never needs fire sprinklers if the main house isn't required to have them. Where they are required, Snap ADU puts design and installation at $5,000 to $10,000.
• Contingency. Maxable advises adding at least 10% over the estimated construction cost. Conversions hide surprises in the slab and walls.

For what the rules allow (setbacks, parking, size), read our garage conversion ADU guide. To run your own numbers, try the ADU cost calculator.

How to lower the cost of a garage conversion

• Start with a sound, permitted garage. Snap ADU says garages built in the last few years can often be converted without much extra money, while 30-plus-year-old garages often cost more to fix than to replace.
• Keep the footprint. A conversion within the existing walls skips setbacks and new foundation work.
• Put the kitchen and bath near the sewer line. Every foot of trench through the slab is labor.
• Share utilities. State law doesn't let the city require a separate connection for a conversion.
• Stay under 500 sq ft if you can. That avoids school fees, and under 750 avoids state impact fees.
• Choose finishes deliberately. Maxable estimates finishes at about 30% of construction cost.
• Get three bids on the same plans, and check a contractor's license before you sign. Our guide on how to hire an ADU contractor covers deposits and payment schedules.

Paying for a garage conversion

Common ways to pay are a HELOC, a home equity loan, a cash-out refinance, a construction loan, or a renovation loan such as Fannie Mae HomeStyle or Freddie Mac CHOICERenovation. Locally, the San Diego Housing Commission's ADU Finance Program offers loans up to $250,000 in exchange for renting at an affordable rent for seven years; check its current funding status. The state's CalHFA ADU grant of up to $40,000 has been fully reserved since December 2023. Compare options in our ADU financing guide and the list of ADU grants in California.

When you're ready for bids, compare verified ADU builders in San Diego.

Common questions