In short
- 101 ADU permits since 2020.
- 35 in 2025.
- Typical permit time: 158 days from application to permit (median of 68 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).
- Mission Viejo's state reports include no ADUs for 2018 or 2019.
Permits by year
Permits by year and type (table)
| Year | All ADU permits | Garage conversions | Detached |
|---|---|---|---|
| 2020 | 4 | — | — |
| 2021 | 14 | — | — |
| 2022 | 7 | — | — |
| 2023 | 24 | — | — |
| 2024 | 17 | — | — |
| 2025 | 35 | — | — |
“—” means the source for that year does not report ADU type.
Read more: ADU types explained
Not counted above: 6 approved projects with no building permit reported yet.
ADU rules in Mission Viejo
State law check: No HCD review letter on file. The code requires a recorded covenant on every ADU and replacement parking for a junior ADU in a garage, the kinds of rules HCD has told other cities state law doesn't allow.
| Rule | Mission Viejo's code | State law guarantees |
|---|---|---|
| Maximum size | 1,200 sq ft for a new detached ADU; attached ADUs 50% of the house, but at least 800 sq ft (city FAQ). 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 | Single-story detached ADU: 20 ft. Two-story attached ADU: 35 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 | Detached ADUs only in the rear half of the lot; the code states no other ADU setbacks. | No more than 4 ft side and rear; none for conversions of existing space. |
| Parking | At most 1 space per ADU or per bedroom, none if exempt (city FAQ). A junior ADU made from an attached garage must replace the 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 permitted since 2020. 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 | An ADU and a junior ADU, processed under state law. | 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, under a recorded covenant. | No guarantee: cities may require rentals of more than 30 days, and junior ADUs can't be short-term rentals. |
- An attached ADU's entrance must be on the side or rear, not facing the same street as the house's.
- ADUs must be architecturally compatible with the house and the neighborhood.
- Lot coverage is capped at 60% on single-family lots, but it can't block an 800 sq ft ADU.
Where local rules conflict with state law, state law controls. Sources: Mission Viejo Municipal Code 9.10.020(12) · City ADU FAQ (Jan 2023); HCD's list of review letters; California ADU rules. Verified Oct 5, 2026. Rules change and every lot is different: confirm with the city before you design.
How long permits take
| Type | Median days, application to permit | Middle half | Permits |
|---|---|---|---|
| Unclassified | 158 | 94 – 236 | 68 |
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 49 ADU permits Mission Viejo reported issuing from 2020 through 2023, 26 (53%) have a completion reported to the state. For those, the median time from permit to completion was 10 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 Mission Viejo? Feature your business on this page.
Questions about ADUs in Mission Viejo
How many ADUs have been permitted in Mission Viejo?
Public records show 101 ADU permits in Mission Viejo from 2020 through 2025. 35 in 2025. 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 Mission Viejo?
Among the 68 ADU permits in Mission Viejo with both dates recorded, half were issued within 158 days of the application; the middle half took 94 to 236 days. That includes plan-check corrections and resubmittals, not just the review itself.
Can I build an ADU on my property in Mission Viejo?
California law allows ADUs on most lots with a house, including in Mission Viejo, 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 Mission Viejo?
Apply with the City of Mission Viejo's Building Services division through its Client Self Service online portal; ADUs need only a building permit. 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.