In short
- 1,128 ADU permits since 2018.
- 211 in 2025, up 1% from 2024.
- Typical permit time: 131 days from application to permit (median of 341 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).
Permits by year
Permits by year and type (table)
| Year | All ADU permits | Garage conversions | Detached |
|---|---|---|---|
| 2018 | 41 | — | — |
| 2019 | 26 | — | — |
| 2020 | 87 | — | — |
| 2021 | 122 | — | — |
| 2022 | 237 | — | — |
| 2023 | 196 | — | — |
| 2024 | 208 | — | — |
| 2025 | 211 | 0 | 0 |
“—” means the source for that year does not report ADU type.
Read more: ADU types explained
Not counted above: 478 approved projects with no building permit reported yet.
ADU rules in Westminster
State law check: HCD found the city's 2021 ADU ordinance out of line with state law (March 3, 2023) and followed up (December 18, 2023); the city updated its ADU rules November 12, 2025, and no HCD letter on the new version is on file.
| Rule | Westminster's code | State law guarantees |
|---|---|---|
| Maximum size | Attached: 1,200 sq ft or 50% of the house, whichever is less, but at least 850 sq ft (1 bedroom) or 1,000 sq ft (2+ bedrooms). Detached: 1,200 sq ft. No cap for conversions. 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: 16 ft (18 ft near transit, plus 2 ft for roof pitch). Attached: 25 ft or the zone limit, 2 stories. | 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; front setback matches the zone. 6 ft between a new detached ADU and other buildings. None for conversions. | No more than 4 ft side and rear; none for conversions of existing space. |
| Parking | 1 space unless the ADU is a studio or exempt (transit, historic district, car share, inside existing space). No replacement parking for converted garages. | 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, with a deed restriction. | 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 | Under the local rules, one ADU or one junior ADU. Under the state-law approvals in the code, a converted ADU plus a junior ADU, or an 800 sq ft detached 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, 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. |
- New ADUs must match the house's materials, colors and roof type, with shielded lighting.
- New ADUs are barred where the City Engineer maps water or sewer service as insufficient, except state-law ADUs.
- Separate utility connections are required, except for conversions inside the house.
Where local rules conflict with state law, state law controls. Sources: Westminster Municipal Code 17.400.135 · HCD findings (March 3, 2023) · HCD letter (December 18, 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 |
|---|---|---|---|
| Junior ADU (JADU) | not reported | ||
| Unclassified | 131 | 97 – 216 | 341 |
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 540 ADU permits Westminster reported issuing from 2020 through 2023, 358 (66%) have a completion reported to the state. For those, the median time from permit to completion was 7 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 Westminster? Feature your business on this page.
Questions about ADUs in Westminster
How many ADUs have been permitted in Westminster?
Public records show 1,128 ADU permits in Westminster from 2018 through 2025. 211 in 2025, up 1% 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 Westminster?
Among the 341 ADU permits in Westminster with both dates recorded, half were issued within 131 days of the application; the middle half took 97 to 216 days. That includes plan-check corrections and resubmittals, not just the review itself.
Can I build an ADU on my property in Westminster?
California law allows ADUs on most lots with a house, including in Westminster, 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 Westminster?
Apply with the City of Westminster's Community Development Department, which reviews ADUs through a zoning clearance and building plan check. 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.