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.
Unincorporated Los Angeles County (Los Angeles County) reported 1,298 ADU building permits in 2025, 28% more than the 1,013 it reported in 2024. That compares with 128 in 2018. The busiest year in this data was 2025, with 1,298 permits. ADUs made up 41.5% of all new homes permitted in Unincorporated Los Angeles County in 2025; statewide the figure was about 26%.
ADU permits in Unincorporated Los Angeles County 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 | 128 | 633 | 20.2% |
| 2019 | 594 | 1,284 | 46.3% |
| 2020 | 397 | 948 | 41.9% |
| 2021 | 574 | 2,084 | 27.5% |
| 2022 | 669 | 1,762 | 38.0% |
| 2023 | 1,044 | 3,026 | 34.5% |
| 2024 | 1,013 | 2,087 | 48.5% |
| 2025 | 1,298 | 3,131 | 41.5% |
ADU rules in Unincorporated Los Angeles County
Official rules: LA County Planning: Accessory Dwelling Units checked Oct 2026. State law sets the floor; see the HCD ADU Handbook.
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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.