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.
Berkeley (Alameda County) reported 116 ADU building permits in 2025, 14% more than the 102 it reported in 2024. That compares with 81 in 2018. The busiest year in this data was 2021, with 121 permits. ADUs made up 25.1% of all new homes permitted in Berkeley in 2025; statewide the figure was about 26%.
ADU permits in Berkeley 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 | 81 | 380 | 21.3% |
| 2019 | 88 | 363 | 24.2% |
| 2020 | 110 | 766 | 14.4% |
| 2021 | 121 | 506 | 23.9% |
| 2022 | 112 | 887 | 12.6% |
| 2023 | 95 | 431 | 22.0% |
| 2024 | 102 | 731 | 14.0% |
| 2025 | 116 | 462 | 25.1% |
ADU rules in Berkeley
We keep a sourced summary of local rules on our Berkeley ADU rules page. The official source is Berkeley Municipal Code 23.306.030 (ADU Development Standards).
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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.