In short
- 2,395 ADU permits since 2018.
- 398 in 2025, down 21% from 2024.
- Typical permit time: 132 days from application to permit (median of 124 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 San Diego County covers the parts of the county outside any city, such as Casa de Oro-Mount Helix, La Presa, Fallbrook, Spring Valley and Bonita. 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.
Permits by year
Permits by year and type (table)
| Year | All ADU permits | Garage conversions | Detached |
|---|---|---|---|
| 2018 | 110 | — | — |
| 2019 | 137 | — | — |
| 2020 | 140 | 0 | 0 |
| 2021 | 306 | — | — |
| 2022 | 345 | — | — |
| 2023 | 457 | — | — |
| 2024 | 502 | — | — |
| 2025 | 398 | — | — |
“—” means the source for that year does not report ADU type.
Read more: ADU types explained
Not counted above: 35 approved projects with no building permit reported yet.
By community
Where these ADU permits are, by community. The most active are Casa de Oro-Mount Helix, La Presa and Fallbrook.
| Community | ADU permits | Share |
|---|---|---|
| Casa de Oro-Mount Helix | 149 | 6% |
| La Presa | 136 | 6% |
| Fallbrook | 114 | 5% |
| Spring Valley | 109 | 5% |
| Bonita | 106 | 4% |
| Fairbanks Ranch | 83 | 3% |
| Rancho San Diego | 76 | 3% |
| Ramona | 75 | 3% |
| Winter Gardens | 71 | 3% |
| Valley Center | 63 | 3% |
| Alpine | 56 | 2% |
| Bostonia | 54 | 2% |
| 20 other communities (listed below) | 312 | 13% |
| Outside any designated community | 990 | 41% |
| Location not available | 1 | <1% |
Show the other 20 communities
| Community | ADU permits | Share |
|---|---|---|
| Lakeside | 53 | 2% |
| Eucalyptus Hills | 42 | 2% |
| Bonsall | 37 | 2% |
| San Diego Country Estates | 36 | 2% |
| Rancho Santa Fe | 34 | 1% |
| Jamul | 18 | 1% |
| Hidden Meadows | 17 | 1% |
| Granite Hills | 15 | 1% |
| Harbison Canyon | 15 | 1% |
| Lake San Marcos | 14 | 1% |
| Crest | 8 | <1% |
| Elfin Forest | 7 | <1% |
| Borrego Springs | 3 | <1% |
| Del Dios | 3 | <1% |
| Descanso | 3 | <1% |
| Campo | 2 | <1% |
| Pine Valley | 2 | <1% |
| Harmony Grove | 1 | <1% |
| Julian | 1 | <1% |
| Rainbow | 1 | <1% |
Communities are Census designated places, matched from each permit's location.
ADU rules in Unincorporated San Diego County
State law check: HCD found the county's ADU rules out of line with state law (July 7, 2026), including its limit on ADU combinations, junior ADU owner-occupancy and replacement parking; the county had until August 6, 2026 to respond.
| Rule | Unincorporated San Diego County's code | State law guarantees |
|---|---|---|
| Maximum size | Detached: 1,200 sq ft. Attached: 50% of the house up to 1,200 sq ft, but at least 850 sq ft (1,000 sq ft with more than one bedroom). Conversions of existing permitted space: no cap. 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 | Detached: 25 ft. An ADU of 800 sq ft or less: 18 ft. Detached ADUs on apartment lots: 18 ft. | 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 for new ADUs, plus any fire setbacks; 4 ft street side on corner lots. None for conversions except fire safety. An ADU of 800 sq ft or less may sit in the front setback. | No more than 4 ft side and rear; none for conversions of existing space. |
| Parking | 1 space for a new detached ADU when the house already exists and the lot is more than ½ mile from transit; none for an ADU of 800 sq ft or less. No replacement when a garage becomes an ADU, but the house's 2 spaces must be replaced when a garage becomes a junior ADU. | 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. Junior ADU: the owner lives in the house or the junior ADU. | 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 new detached ADU, one ADU converted from existing space 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 | 30 days or more, for ADUs and junior ADUs. | No guarantee: cities may require rentals of more than 30 days, and junior ADUs can't be short-term rentals. |
- A Director's Determination (January 29, 2025) says state law controls wherever the county zoning ordinance conflicts with it.
- The county's ADU impact-fee waiver ended January 9, 2024.
- The county offers detached ADU building plans that are about 85% complete.
- Since March 4, 2026, ADUs can be sold separately as condominiums through a parcel or tentative map.
- Check with the local fire district early: it sets fire setbacks and whether sprinklers or a hydrant are needed.
Where local rules conflict with state law, state law controls. Sources: County of San Diego PDS-611 ADU/JADU handout (Rev. September 2, 2026) · County of San Diego ADU page · HCD findings (July 7, 2026) · PDS Director's Determination (January 29, 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
| Type | Median days, application to permit | Middle half | Permits |
|---|---|---|---|
| Junior ADU (JADU) | not reported | ||
| Unclassified | 132 | 66 – 187 | 124 |
Middle half: the range covering the middle 50% of permits (a quarter were lower, a quarter higher).
Read more: How long ADUs take to build
From permit to completion
Of the 1,178 ADU permits Unincorporated San Diego County reported issuing from 2020 through 2023, 941 (80%) have a completion reported to the state. For those, the median time from permit to completion was 12 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 San Diego County? Feature your business on this page.
Questions about ADUs in Unincorporated San Diego County
How many ADUs have been permitted in Unincorporated San Diego County?
Public records show 2,395 ADU permits in Unincorporated San Diego County from 2018 through 2025. 398 in 2025, down 21% 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 San Diego County?
Among the 124 ADU permits in Unincorporated San Diego County with both dates recorded, half were issued within 132 days of the application; the middle half took 66 to 187 days. That includes plan-check corrections and resubmittals, not just the review itself.
Can I build an ADU on my property in Unincorporated San Diego County?
California law allows ADUs on most lots with a house, including in Unincorporated San Diego 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 San Diego County?
Apply with the County of San Diego's Planning & Development Services for a building permit; the county also offers ready-made detached 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.