What is an ADU? An ADU (accessory dwelling unit) is a small second home on the same lot as a house, with its own kitchen and bathroom. Granny flats, in-law units, backyard cottages and garage conversions are all ADUs. More on what counts.
San Diego (San Diego County) reported 2,165 ADU building permits in 2025, 5% fewer than the 2,281 it reported in 2024. That compares with 216 in 2018. The busiest year in this data was 2024, with 2,281 permits. ADUs made up 28.4% of all new homes permitted in San Diego in 2025; statewide the figure was about 26%.
ADU permits in San Diego by year
Source: HCD Housing Element Annual Progress Report, Table A2 (data.ca.gov) checked Oct 2026. Our count, see method.
| Year | ADU permits | All homes permitted | ADU share |
|---|---|---|---|
| 2018 | 216 | 3,895 | 5.5% |
| 2019 | 625 | 4,862 | 12.9% |
| 2020 | 491 | 6,482 | 7.6% |
| 2021 | 870 | 5,032 | 17.3% |
| 2022 | 656 | 5,322 | 12.3% |
| 2023 | 1,908 | 9,690 | 19.7% |
| 2024 | 2,281 | 8,782 | 26.0% |
| 2025 | 2,165 | 7,630 | 28.4% |
ADU rules in San Diego
We keep a sourced summary of local rules on our San Diego ADU rules page. The official source is City of San Diego: Information Bulletin 400 (Jan 2026).
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Method
- Counts are building permits for units the jurisdiction reported as ADUs, with an issue date in the report year, after removing exact duplicate rows. Same method as our California ADU Data page.
- Permits are not finished homes. 2025 filings were due in April 2026, and late or corrected filings can change the numbers.