What a garage conversion ADU costs in San Diego
How much does a garage conversion ADU cost in San Diego?
Garage and other conversion ADUs in the City of San Diego declared a median $89,600 of construction in 2026 (middle half $59,600–$144,400, 307 permits), about $64,700 less than a new detached ADU. Declared value leaves out design, City fees and utility work.
In 2026, 307 City of San Diego building permits converted a garage, room or accessory building into an ADU. The median declared construction value was $89,600.
| ADU type | Permits | Low (25%) | Median | High (75%) |
|---|---|---|---|---|
| Conversion | 307 | $59,600 | $89,600 | $144,400 |
| New detached ADU | 293 | $102,900 | $154,300 | $198,800 |
| Any single ADU | 750 | $76,000 | $120,900 | $197,700 |
Source: City of San Diego permit data (building permits issued Jan 1–Oct 15, 2026 that add at least one ADU). Valuation is the construction value the applicant declared to the City, not a final invoice or a quote. Types are sorted by words in the permit description.
Why conversions run lower
Typical conversion medians were about $64,700 less than new detached ADUs ($89,600 vs $154,300), because the walls, roof and slab already exist. Budgets still swing on what the existing structure needs: foundation and framing upgrades, insulation, windows, a new kitchen and bath, and utility runs.
Not in the permit value
Design, structural engineering, the Title 24 energy report, City fees, utility work (sewer lateral, meter, panel) and undeclared finishes are often left out. Ask every builder to price these line by line, and use the fair-quote checklist.
Fees to expect
- Development Impact Fees are waived for ADUs under 750 sq ft and for the first two ADUs on a property (SDMC §142.0640).
- Water and sewer capacity fees are separate and depend on the design, such as a new connection or meter.
- School fees, the General Plan Maintenance Fee and plan check/permit fees still apply. See the full fee notes.
How long the permit takes
Across 1,037 standard-track ADU permits issued in 2026, the median was 293 days from application to issue (fastest quarter 170 days or less; slowest quarter 486 days or more). Correction rounds are usually the longest part. Full timeline.