California ADU Statistics: Permits by Year, County and City

The numbers at a glance

How many ADUs did California permit in 2025?

41,847, against 9,000 in 2018. That is a 4.6-fold increase in seven years, and it is the reason ADUs stopped being a niche product and became a normal part of how California adds housing. The chart shows the whole series; the table adds each year’s share of total new-home permits.

Source: California HCD, Annual Progress Report Table A2 (units with building permits issued), queried August 2026.

Is California’s ADU boom slowing down?

Yes, and the deceleration is steady rather than sudden. Year-over-year growth ran +29.2% in 2022, +12.3% in 2023, +11.0% in 2024 and +5.6% in 2025. The absolute number is still climbing and 2025 was the highest year on record, so this is maturation rather than decline: the easiest sites have been built, construction costs are higher than they were in 2021, and the cities that were going to adopt friendly ordinances mostly have. For a homeowner the practical read is that the competitive advantage of moving early has narrowed, and the advantage of building well has widened.

What share of new California homes is an ADU?

26.0% in 2025, up from 15.5% in 2021. Roughly one in every four homes the state permits is now a backyard or converted unit rather than a house or an apartment. That share has risen every single year of the series, which is a different trend from the permit count and worth separating: even as ADU growth slows, ADUs are taking a larger slice of a shrinking overall housing pipeline.

Which California counties build the most ADUs?

Los Angeles County, by a distance that surprises people. Its 19,958 permits in 2025 exceed the next five counties combined. Southern California as a whole (Los Angeles, Orange, Riverside and San Bernardino) accounts for the clear majority of the state’s ADU activity.

Top seven counties by 2025 ADU building permits, same source as above.

Which Orange County city issues the most ADU permits?

Fullerton, with 589 in 2025. The more interesting number is the county total: Orange County went from 2,879 permits in 2024 to 3,071 in 2025, still growing but at 6.7% against 20.0% the year before. It is small enough that one year does not make a trend, but it is worth watching, and it sits alongside a statewide slowdown rather than contradicting it. City-level counts also move sharply year to year: Buena Park more than doubled, from 86 to 179, while Westminster stopped filing altogether.

Top 15 Orange County jurisdictions by 2025 ADU permits, as reported to HCD by each city. A few cities’ most recent filings appear incomplete in the state dataset; figures reflect what each jurisdiction reported.

Which Los Angeles County cities build the most?

The City of Los Angeles alone permitted 12,328 ADUs in 2025, which is more than every county in the state except Los Angeles County itself and San Diego. Among the smaller cities we build in, Long Beach and Lakewood lead. Lakewood is the standout: 498 permits in 2025 against 197 in 2024, a two-and-a-half-fold jump in a single year.

Same source and metric as above; jurisdiction-reported.

How should you read these numbers?

Carefully, and this is the section most ADU statistics pages leave out. Four limits are worth knowing before you quote any of this, including quoting it back to us.

• These are permits issued, not units built. A permit can lapse, and construction can start in a later year than the permit. Treat the series as a measure of intent and approval, not of finished homes.
• Cities self-report. The Annual Progress Report is filed by each jurisdiction. Some file late, some file incompletely, and some do not file at all in a given year. Westminster reported 232 ADUs in 2024 and nothing for 2025, which is a filing gap rather than a collapse in building.
• Some counts are not credible on their face. Irvine reports 8 ADU permits for 2025 and 15 across the entire 2018 to 2025 period. For a city of its size that is a reporting artifact, not a measure of local activity. Where a city’s own filings look incomplete we say so rather than repeating the number.
• The category is broad. UNIT_CAT ‘ADU’ covers detached units, attached units, garage conversions and JADUs together. The data does not split them, so no honest source can tell you from this dataset how many of the 41,847 were detached.

Check it yourself. The reporting duty comes from Government Code section 65400, which requires every city and county to file an annual report with HCD by April 1 covering, among other things, the number of units issued a building permit. HCD publishes what they file on its APR dashboard, and the raw table sits on data.ca.gov for anyone to query.

A worked example of why the late-filing caveat matters. When we first built this page in August 2026 the dataset gave Orange County 2,879 permits for 2024 and 2,856 for 2025, and we published that as the county’s first year-over-year decline. Re-querying the same dataset in September 2026 returns 3,071 for 2025, because more jurisdictions had filed in the interim. There was no decline. We have corrected it here, and we are leaving the episode on the page because it is the clearest illustration we have that a recent year in this dataset is provisional until the filings settle.

What do the numbers mean if you own a home here?

Three things follow from the data rather than from opinion. First, the approval path works: 41,847 permits in a single year is not a jurisdiction quietly refusing, it is a state-level process that is functioning at scale. Second, your city’s own count is a reasonable proxy for how practised its plan-check staff are. A city issuing hundreds of ADU permits a year has seen your project before, and that usually shows in the correction rounds. Third, the slowdown changes what competitive advantage looks like: when volume was doubling, being early mattered; now that it is growing at 5%, the unit that rents well is the one that was designed and built properly. Each of our city pages carries that city’s own 2018 to 2025 series so you can look up your own. From there the practical next steps are the three questions every owner asks: what it costs (our 2026 cost guide), what your city allows (the rules by city), and what fits the yard (ADU floor plans by size).