How many ADUs California permits, where, and what they cost to build and rent. Every number links to its public source, and the method is spelled out so you can check it.
ADU building permits by year
Source: HCD Housing Element Annual Progress Report (APR) Table A2, data.ca.gov checked Oct 2026. Our count, see method below.
Permits rose from 8,905 in 2018 to 30,478 in 2024 and 32,174 in 2025 in the reports cities and counties filed. HCD's own ADU Handbook (March 2026) reports 30,354 ADUs permitted in 2024, up from 1,336 in 2016, and says ADUs were more than 26.6% of all homes permitted statewide in 2024 (HCD ADU Handbook). Our 2024 count is within 0.5% of that.
ADUs as a share of all permitted homes
Same APR data: ADU permits divided by permits for all unit types (single-family, 2 to 4, 5+, ADU, mobile home).
Top 10 jurisdictions by ADU permits, 2024
Cities and unincorporated counties as named in APR filings. Los Angeles County and San Diego County mean unincorporated areas only.
What ADUs cost to build
Median construction cost by region. Source: UC Berkeley Terner Center, Implementing the Backyard Revolution (Apr 2021) checked Oct 2026. Statewide median $150,000, or $250 per sq ft; 37% cost under $100,000 and 71% under $200,000. Average new ADU: 615 sq ft.
What ADUs rent for
The same survey found a median ADU rent of $2,000 a month, from $1,925 on the Central Coast to $2,200 in the SF Bay Area, or $3.68 per sq ft. These figures are from a 2020 owner survey and are not adjusted for inflation; today's prices are likely different.
Method
- We downloaded APR Table A2 (every permitted unit reported by every California city and county) from data.ca.gov in October 2026.
- We counted rows with unit category ADU, kept only permits whose issue date falls in the report year, and dropped exact duplicate rows (same jurisdiction, parcel, address, tracking ID and date). Counting every row without that filter gives higher totals (39,073 for 2024), because some reports repeat permits from earlier years.
- 2025 reports were due in April 2026; late filings could still change the 2025 numbers.
- This is a count of reported permits, not an index or a forecast. Permits are not finished homes.
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