In short
- 5,762 ADU permits since 2018.
- 1,181 in 2025, up 22% from 2024.
- Typical permit time: 301 days from application to permit (median of 3,597 permits with both dates recorded).
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 Los Angeles County covers the parts of the county outside any city, such as Altadena, East Los Angeles, Hacienda Heights, Rowland Heights and the Antelope Valley's rural areas. The county reports them together; its page breaks them down by community using each permit's location (Census designated places). Addresses show the postal city, which is often a nearby city's name.
Permits by year
Permits by year and type (table)
| Year | All ADU permits | Garage conversions | Detached |
|---|---|---|---|
| 2018 | 144 | — | — |
| 2019 | 595 | — | — |
| 2020 | 561 | — | — |
| 2021 | 618 | — | — |
| 2022 | 670 | — | — |
| 2023 | 1,022 | 0 | 1 |
| 2024 | 971 | 4 | 4 |
| 2025 | 1,181 | — | — |
“—” means the source for that year does not report ADU type.
Read more: ADU types explained
Not counted above: 4,638 approved projects with no building permit reported yet.
By community
Where these ADU permits are, by community. The most active are Altadena, East Los Angeles and South Whittier.
| Community | ADU permits | Share |
|---|---|---|
| Altadena | 691 | 12% |
| East Los Angeles | 515 | 9% |
| South Whittier | 303 | 5% |
| Hacienda Heights | 272 | 5% |
| Rowland Heights | 253 | 4% |
| Florence-Graham | 236 | 4% |
| East San Gabriel | 227 | 4% |
| La Crescenta-Montrose | 207 | 4% |
| Westmont | 197 | 3% |
| Valinda | 166 | 3% |
| Del Aire | 152 | 3% |
| West Whittier-Los Nietos | 149 | 3% |
| 36 other communities (listed below) | 1,864 | 32% |
| Outside any designated community | 526 | 9% |
| Location not available | 4 | <1% |
Show the other 36 communities
| Community | ADU permits | Share |
|---|---|---|
| West Rancho Dominguez | 144 | 2% |
| Lennox | 135 | 2% |
| Walnut Park | 125 | 2% |
| West Puente Valley | 125 | 2% |
| View Park-Windsor Hills | 109 | 2% |
| East Rancho Dominguez | 95 | 2% |
| East Pasadena | 88 | 2% |
| Mayflower Village | 79 | 1% |
| South San Jose Hills | 78 | 1% |
| Avocado Heights | 77 | 1% |
| South Monrovia Island | 77 | 1% |
| Vincent | 77 | 1% |
| Willowbrook | 77 | 1% |
| Alondra Park | 74 | 1% |
| South San Gabriel | 71 | 1% |
| West Carson | 57 | 1% |
| West Athens | 55 | 1% |
| North El Monte | 46 | 1% |
| Ladera Heights | 41 | 1% |
| Citrus | 33 | 1% |
| Quartz Hill | 31 | 1% |
| Charter Oak | 30 | 1% |
| Sun Village | 26 | <1% |
| San Pasqual | 21 | <1% |
| East Whittier | 19 | <1% |
| Castaic | 17 | <1% |
| Topanga | 13 | <1% |
| Desert View Highlands | 10 | <1% |
| Acton | 9 | <1% |
| Lake Los Angeles | 6 | <1% |
| Littlerock | 5 | <1% |
| Hasley Canyon | 3 | <1% |
| Leona Valley | 3 | <1% |
| Rose Hills | 3 | <1% |
| Stevenson Ranch | 3 | <1% |
| Agua Dulce | 2 | <1% |
Communities are Census designated places, matched from each permit's location.
ADU rules in Unincorporated Los Angeles County
State law check: HCD found the county's July 2025 ordinance noncompliant (December 1, 2025), including its unit allowances, front-yard siting rule and attached-ADU height; the county responded and is drafting a 2026 amendment. HCD also questioned its fire-zone access rule (June 22, 2023). State law governs where they differ.
| Rule | Unincorporated Los Angeles County's code | State law guarantees |
|---|---|---|
| Maximum size | 1,200 sq ft; no cap for an ADU inside an existing home or converted from an accessory building. State-law detached ADU 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 | 25 ft, attached or detached, unless a community standards district or specific plan sets less (it must still allow 16 ft, or 18 ft near transit plus 2 ft for roof pitch). Lower near scenic routes. | 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 rear, interior side and corner side; none for conversions. An ADU up to 800 sq ft may go in the front yard only if there's no other ground-level spot. | No more than 4 ft side and rear; none for conversions of existing space. |
| Parking | None outside Very High Fire Hazard Severity Zones. Inside them, parking per the county code unless exempt (no bedroom, transit, inside existing space and others). 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 for ADUs; the county released old ADU owner-occupancy covenants. Junior ADU: the owner lives in the house or the junior ADU, with a covenant; none on corporate-owned lots. | 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 | One ADU attached to or within the house, one detached ADU and one 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 | More than 30 consecutive days, for ADUs and junior ADUs. No home businesses in an ADU. | No guarantee: cities may require rentals of more than 30 days, and junior ADUs can't be short-term rentals. |
- Very High Fire Hazard Severity Zones: most new ADUs need two separate 24 ft wide routes to a highway (or frontage on one); state-law ADUs are exempt.
- After the Eaton and Palisades fires, an owner may live in an ADU on a destroyed-home lot while rebuilding, until January 7, 2030.
- Coastal Zone lots (Marina del Rey, the Santa Monica Mountains) follow the Local Coastal Program. Free county ADU plans (800 and 1,200 sq ft) are available.
Where local rules conflict with state law, state law controls. Sources: LA County Code § 22.140.640 (Ord. 2025-0029, adopted Jul 29, 2025) · HCD findings (Dec 1, 2025) · HCD letter on fire zones (Jun 22, 2023) · LA County Planning Interpretation No. 2025-04 (Apr 23, 2025) · LA County 2026 ADU Ordinance Amendment; HCD's list of review letters; California ADU rules. Verified Sep 30, 2026. Rules change and every lot is different: confirm with the county before you design.
How long permits take
| Type | Median days, application to permit | Middle half | Permits |
|---|---|---|---|
| Detached ADU | too few to say | 5 | |
| Attached ADU | too few to say | 2 | |
| Garage conversion | too few to say | 3 | |
| Junior ADU (JADU) | too few to say | 4 | |
| Unclassified | 302 | 182 – 483 | 3,583 |
Middle half: the range covering the middle 50% of permits (a quarter were lower, a quarter higher).
Read more: How long ADU permits take in Los Angeles (and other cities) · How long ADUs take to build
From permit to completion
Of the 2,517 ADU permits Unincorporated Los Angeles County reported issuing from 2020 through 2023, 1,683 (67%) have a completion reported to the state. For those, the median time from permit to completion was 13 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 Los Angeles County? Feature your business on this page.
Questions about ADUs in Unincorporated Los Angeles County
How many ADUs have been permitted in Unincorporated Los Angeles County?
Public records show 5,762 ADU permits in Unincorporated Los Angeles County from 2018 through 2025. 1,181 in 2025, up 22% 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.
How long does an ADU permit take in Unincorporated Los Angeles County?
Among the 3,597 ADU permits in Unincorporated Los Angeles County with both dates recorded, half were issued within 301 days of the application; the middle half took 182 to 483 days. That includes plan-check corrections and resubmittals, not just the review itself.
Can I build an ADU on my property in Unincorporated Los Angeles County?
California law allows ADUs on most lots with a house, including in Unincorporated Los Angeles 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 Los Angeles County?
Apply with LA County Planning for a plot plan review, then with LA County Public Works Building and Safety for the building permit; the county's standard ADU plans are free. 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.