San Diego ADU price guide
What does an ADU cost in San Diego, including fees?
2026 City of San Diego permits put the median single-ADU construction value at $120,900 (750 permits). ADUs under 750 sq ft and the first two ADUs on a lot are exempt from Development Impact Fees, but school fees, plan check and permit fees still apply.
Every number below comes from City of San Diego records or official City pages. Where we estimate, we say so.
Construction value from 2026 permits
| ADU type (City of SD, 2026) | Permits | Low (25%) | Median | High (75%) |
|---|---|---|---|---|
| Any single-ADU permit | 750 | $76,000 | $120,900 | $197,700 |
| Conversion (garage, room, accessory building) | 307 | $59,600 | $89,600 | $144,400 |
| New detached ADU | 293 | $102,900 | $154,300 | $198,800 |
| Permits adding 2+ ADUs | 333 | $151,300 | $247,200 | $330,300 |
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. “Conversion” and “detached” are sorted by words in the permit description; some permits also include work on the main house.
Fees: what's waived and what isn't
- Development Impact Fees (DIF): exempt for ADUs under 750 sq ft and for the first two ADUs on a property, regardless of size. A third or later ADU of 750 sq ft or more pays the multi-unit rate. (City of SD impact fee FAQ, SDMC §142.0640)
- Water and sewer capacity fees: not covered by the 750 sq ft rule; they depend on the design, such as whether you add a new connection or meter. (City Attorney memo MS-2020-20)
- School fees, General Plan Maintenance Fee, and plan check/permit fees still apply. Projects with more than one ADU also pay the regional transportation (RTCIP) fee. (Information Bulletin 400, Jan 2026; full schedule in IB 501)
- California generally exempts additions of 500 sq ft or less from school fees (Education Code §17620). Ask your school district to confirm.
Budget items often missing from the permit value
Estimate guidance, not City data: architect or designer, structural engineering, Title 24 energy report, survey, soils report where needed, utility work (sewer lateral, meter, panel), and finishes or appliances the applicant didn't declare. Ask each builder to price these line by line.
See garage conversion costs and detached ADU costs · Compare up to 3 local ADU quotes → · See ADU data on the San Diego price hub