In short
- 451 ADU permits since 2018.
- 102 in 2025, up 40% from 2024.
About this data
- Source: California HCD Housing Element Annual Progress Reports. The state data does not say whether an ADU is detached, attached, a garage conversion or a JADU, so most records show as 'unknown'. Permit valuations are not published in this source. Timelines use the application date the city reported to the state, matched to the permit where possible; some cities report their planning application date, so timelines can include planning review. Each project is counted once, in its building-permit year (or completion year when no permit date was reported).
- Unincorporated Orange County covers the parts of the county outside any city, such as North Tustin, Midway City, Rossmoor and El Modena. The county reports them together; its page breaks them down by community using each permit's location (Census designated places), with rural areas counted separately. Addresses show the postal city, which is often a nearby city's name.
- Unincorporated Orange County reported far fewer ADUs for 2021 than for the years around it; that year likely understates permit activity.
Permits by year
Permits by year and type (table)
| Year | All ADU permits | Garage conversions | Detached |
|---|---|---|---|
| 2018 | 26 | — | — |
| 2019 | 21 | — | — |
| 2020 | 57 | — | — |
| 2021 (incomplete report) | 15 | — | — |
| 2022 | 84 | — | — |
| 2023 | 73 | — | — |
| 2024 | 73 | — | — |
| 2025 | 102 | 0 | 0 |
“—” means the source for that year does not report ADU type.
Read more: ADU types explained
By community
Where these ADU permits are, by community. The most active are North Tustin, Midway City and Rossmoor.
| Community | ADU permits | Share |
|---|---|---|
| North Tustin | 138 | 31% |
| Midway City | 72 | 16% |
| Rossmoor | 21 | 5% |
| El Modena | 17 | 4% |
| Coto de Caza | 8 | 2% |
| Orange Park Acres | 7 | 2% |
| Ladera Ranch | 5 | 1% |
| Modjeska | 2 | <1% |
| Silverado | 1 | <1% |
| Trabuco Canyon | 1 | <1% |
| Williams Canyon | 1 | <1% |
| Outside any designated community | 178 | 39% |
Communities are Census designated places, matched from each permit's location.
ADU rules in Unincorporated Orange County
State law check: HCD sent a technical-assistance letter (December 5, 2025) noting the county's 2020 ordinance on file may be outdated; no formal findings. The county responded; its fact sheet (January 2026) follows current state law.
| Rule | Unincorporated Orange County's code | State law guarantees |
|---|---|---|
| Maximum size | Attached: 50% of the house, up to 1,200 sq ft. Detached: 1,200 sq ft. Built in a setback area: 800 sq ft. Junior ADU 500 sq ft. | At least 850 sq ft (1,000 sq ft with 2+ bedrooms) must be allowed; an 800 sq ft detached ADU always is. Conversions of existing space have no size cap. Junior ADU: up to 500 sq ft. |
| Height | The zone's limit in the buildable area; 16 ft in a setback area (18 or 25 ft where state law allows). | Detached: at least 16 ft (18 ft within ½ mile of transit, plus 2 ft for a matching roof). Attached: 25 ft or the zone's limit, whichever is lower. |
| Setbacks | 4 ft side and rear; in the front setback only as needed for an 800 sq ft ADU, at least 4 ft from the front line. None for conversions. | No more than 4 ft side and rear; none for conversions of existing space. |
| Parking | 1 space per ADU, unless exempt (transit, historic area, inside existing space, car share, no bedrooms). None for junior ADUs; no replacement parking. | At most 1 space; none within ½ mile of transit and in several other cases. No replacement parking when a garage is converted. |
| Owner living on site | None stated for ADUs. Junior ADU: the owner must live on the site. | None for ADUs. A junior ADU that shares a bathroom with the house requires the owner to live in one of them. |
| How many on a single-family lot | Up to three: one converted ADU, one new detached ADU and one junior ADU (county fact sheet); the 2020 code text still says one ADU plus a junior ADU. | One ADU converted from existing space, one junior ADU and one new detached ADU (up to 800 sq ft). From January 1, 2027: two new detached ADUs (a city then needn't allow a junior ADU on that lot). |
| Short-term rentals | 30 days or more. | No guarantee: cities may require rentals of more than 30 days, and junior ADUs can't be short-term rentals. |
- The code section still cites older state law (Gov. Code 65852.2); the county's ADU fact sheet describes the rules it applies now.
- ADUs need only a building permit, no separate planning approval.
- The county offers free pre-approved ADU plans.
Where local rules conflict with state law, state law controls. Sources: Orange County Zoning Code 7-9-90 · County ADU fact sheet (Jan 2026) · HCD letter (December 5, 2025); HCD's list of review letters; California ADU rules. Verified Oct 5, 2026. Rules change and every lot is different: confirm with the county before you design.
How long permits take
Application and issue dates are not published for this area in these sources.
Read more: How long ADUs take to build
From permit to completion
Of the 168 ADU permits Unincorporated Orange County reported issuing in 2020, 2022 and 2023, 131 (78%) have a completion reported to the state. For those, the median time from permit to completion was 11 months.
The state reports don't record expired or cancelled permits, and a completion the city hasn't reported looks the same as an unfinished project, so the share is a floor. Years with incomplete reports are left out.
What neighbors declared as cost
Cost data (declared permit valuations) is not published for this area in these sources.
Read more: How to choose an ADU builder
An ADU builder serving Unincorporated Orange County? Feature your business on this page.
Questions about ADUs in Unincorporated Orange County
How many ADUs have been permitted in Unincorporated Orange County?
Public records show 451 ADU permits in Unincorporated Orange County from 2018 through 2025. 102 in 2025, up 40% from 2024. These counts come from the city's reports to the state, which place a project in its completion year when no permit date was reported.
Can I build an ADU on my property in Unincorporated Orange County?
California law allows ADUs on most lots with a house, including in Unincorporated Orange County, but what you can build depends on your lot, local rules and utilities. This site shows permits, not eligibility. See California ADU rules.
Where do I apply for an ADU permit in Unincorporated Orange County?
Apply with the County of Orange's OC Development Services through the myOCeServices portal; ADUs need only a building permit, and the county offers pre-approved ADU plans. Official ADU page.
How current is this?
- State annual progress reports: through 2025 (published once a year)
How our data works · Download the data · Free to reuse with credit to SoCal ADU Tracker (socaladutracker.com), under CC BY 4.0.