Garage Conversion ADUs in San Diego
Updated
A garage conversion ADU in San Diego turns an existing garage into a separate home with its own kitchen and bathroom. Because the structure is already there, it can cost less than building new, but it still needs a building permit and has its own rules. Here is what the City of San Diego's rules and published cost guides say.
City rules for garage conversions
- Permit. A building permit is required for every ADU, with no exemptions [1].
- Size. Converting an existing structure is not held to the 1,200 square foot limit that applies to new attached or detached ADUs [1].
- Parking. ADUs outside the Coastal Overlay Zone need no parking [1]. One exception: a garage conversion in the Beach Impact area outside a Transit Priority Area needs one replacement parking space [2].
- No JADU in a detached garage. Since the City's Housing Action Package 2.0, JADUs cannot be built inside detached garages [3]. A detached garage can become an ADU instead.
- Renting. An ADU may not be rented for less than 31 days in a row [1].
What a garage conversion costs
We did not find a published survey of San Diego garage conversion prices, so these are national figures. HomeGuide's 2023 guide lists [4]:
| Item | National range |
|---|---|
| Garage conversion, per square foot | $50 to $200 |
| Full garage conversion | $20,000 to $140,000 |
| Typical project time | 2 to 12 months |
HomeGuide says a conversion involves new floors, walls, windows, insulation, drywall, electrical, plumbing, and HVAC [4]. Its figures are older and national, so local quotes may run higher.
City permit fees depend on size. In the City's August 2026 fee schedule, an attached ADU up to 1,100 square feet, or a detached ADU up to 500 square feet, starts at $3,512.92 for plan check and $2,228.29 for inspection [5]. Impact fees and school fees can be added on top [5]. More detail is on our ADU cost guide.
Things to weigh
- Losing the garage. HomeGuide notes that a conversion may lower home value in areas where garage parking is highly valued [4].
- Plumbing and sewer. A new bathroom and kitchen need drain lines, which can drive cost on some lots.
- Coastal lots. Inside the Coastal Overlay Zone, a Coastal Development Permit is generally required [1].
FAQ
Do I need to replace the parking when I convert my garage?
Usually not in the City of San Diego. No parking is required for ADUs outside the Coastal Overlay Zone [1]. The exception is a garage conversion in the Beach Impact area outside a Transit Priority Area, which needs one replacement space [2]. Check your lot's overlays before you design.
Can I turn my garage into a JADU instead?
Not if it is a detached garage. Since Housing Action Package 2.0, the City does not allow JADUs inside detached garages [3]. A JADU must sit entirely inside the main home [2]. A detached garage can become a full ADU instead.
How long does a garage conversion take?
HomeGuide puts a typical garage conversion at 2 to 12 months [4]. In the City of San Diego, permit review is part of that time. See our rules and permits guide for the steps.
Request a quote for a garage conversion from an independent local contractor.
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Sources
- City of San Diego Development Services, "Information Bulletin 400: Accessory Dwelling Unit/Junior Accessory Dwelling Unit," January 2026. Fetched 2026-11-11. https://www.sandiego.gov/development-services/forms-publications/information-bulletins/400
- City of San Diego Development Services, "Accessory Dwelling Unit/Junior Accessory Dwelling Unit," no date shown. Fetched 2026-11-11. https://www.sandiego.gov/development-services/news-programs/programs/companion-junior-units
- City of San Diego Development Services, "Regulatory Updates," no date shown. Fetched 2026-11-11. https://www.sandiego.gov/development-services/regulatory-updates
- HomeGuide, "How Much Does It Cost to Build an ADU?," November 13, 2023. Fetched 2026-11-11. https://homeguide.com/costs/adu-cost
- City of San Diego Development Services, "Information Bulletin 501: Fee Schedule for Construction Permits," August 2026. Fetched 2026-11-11. https://www.sandiego.gov/development-services/forms-publications/information-bulletins/501