In short
- 586 ADU permits since 2018.
- 117 in 2025, up 60% from 2024.
- Typical permit time: 146 days from application to permit (median of 266 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 | 19 | — | — |
| 2019 | 20 | 0 | 5 |
| 2020 | 40 | 2 | 10 |
| 2021 | 68 | 3 | 27 |
| 2022 | 133 | 1 | 31 |
| 2023 | 116 | 2 | 79 |
| 2024 | 73 | 0 | 1 |
| 2025 | 117 | 1 | 3 |
“—” means the source for that year does not report ADU type.
Read more: ADU types explained
Not counted above: 307 approved projects with no building permit reported yet.
ADU rules in Thousand Oaks
State law check: HCD found the current ordinance (adopted March 10, 2026) noncompliant (June 1, 2026), including counting a locally regulated ADU against the state-law allowance; state law governs where they differ.
| Rule | Thousand Oaks' code | State law guarantees |
|---|---|---|
| Maximum size | Attached or converted: 850 sq ft or 50% of the house, whichever is greater. Detached: 1,000 sq ft. 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 | Detached: 16 ft (18 ft near transit, plus 2 ft). Attached: 25 ft or the zone limit. | 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; the house's front setback; 6 ft between a detached ADU and other buildings. | No more than 4 ft side and rear; none for conversions of existing space. |
| Parking | 1 space unless exempt (transit, conversions, 500 sq ft or less, and others). | 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: only when it shares a bathroom with the house. | 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 | The state-law combinations, but a larger locally regulated ADU counts as one of them. | 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 | Not for 30 days or less. | No guarantee: cities may require rentals of more than 30 days, and junior ADUs can't be short-term rentals. |
- No ADUs on slopes over 25%; ridgeline and oak-tree protections apply.
- Objective design standards: privacy glass within 10 ft of a neighbor, no rooftop decks.
Where local rules conflict with state law, state law controls. Sources: Thousand Oaks Municipal Code §§ 9-4.4501–9-4.4512 (Ord. 1747-NS, adopted Mar 10, 2026) · HCD findings (Jun 1, 2026) · HCD findings (Sep 23, 2025); HCD's list of review letters; California ADU rules. Verified Sep 29, 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 |
|---|---|---|---|
| Detached ADU | 146 | 83 – 231 | 92 |
| Attached ADU | 112 | 65 – 174 | 42 |
| Garage conversion | too few to say | 8 | |
| Junior ADU (JADU) | too few to say | 7 | |
| Unclassified | 161 | 98 – 236 | 117 |
Middle half: the range covering the middle 50% of permits (a quarter were lower, a quarter higher).
Read more: ADU permit times across Ventura County · How long ADUs take to build
From permit to completion
Of the 256 ADU permits Thousand Oaks reported issuing from 2020 through 2023, 76 (30%) have a completion reported to the state. For those, the median time from permit to completion was 5 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 Thousand Oaks? Feature your business on this page.
Questions about ADUs in Thousand Oaks
How many ADUs have been permitted in Thousand Oaks?
Public records show 586 ADU permits in Thousand Oaks from 2018 through 2025. 117 in 2025, up 60% 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 Thousand Oaks?
Among the 266 ADU permits in Thousand Oaks with both dates recorded, half were issued within 146 days of the application; the middle half took 86 to 226 days. That includes plan-check corrections and resubmittals, not just the review itself.
Can I build an ADU on my property in Thousand Oaks?
California law allows ADUs on most lots with a house, including in Thousand Oaks, 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 Thousand Oaks?
Apply with the City of Thousand Oaks: Planning review, then a building plan check and permit through the TO24 portal. 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.