In short
- 566 ADU permits since 2018.
- 192 in 2025.
- Typical permit time: 211 days from application to permit (median of 80 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).
- Simi Valley reported no ADU building-permit dates for 2019 and, for 2020–2024, appears to have reported only completed projects; those are counted in their completion year. Yearly counts likely understate permit activity.
Permits by year
Permits by year and type (table)
| Year | All ADU permits | Garage conversions | Detached |
|---|---|---|---|
| 2018 | 27 | — | — |
| 2019 (incomplete report) | 24 | — | — |
| 2020 (incomplete report) | 52 | — | — |
| 2021 (incomplete report) | 24 | — | — |
| 2022 (incomplete report) | 72 | 0 | 0 |
| 2023 (incomplete report) | 83 | 0 | 0 |
| 2024 (incomplete report) | 92 | — | — |
| 2025 | 192 | — | — |
“—” means the source for that year does not report ADU type.
Read more: ADU types explained
Not counted above: 26 approved projects with no building permit reported yet.
ADU rules in Simi Valley
State law check: HCD found the ordinance noncompliant (October 29, 2025), with 19 findings; the city says it's being updated. State law governs where they differ.
| Rule | Simi Valley's code | State law guarantees |
|---|---|---|
| Maximum size | Detached: 1,000 sq ft on lots up to 8,000 sq ft, 1,200 sq ft on larger lots; 800 sq ft with a junior ADU or in hillside areas. Attached: 50% of the house or 800 sq ft, up to 1,000. 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: one story, 18 ft (plus 2 ft near transit). Attached: 2 stories, 25 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; 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 (studios, transit, inside the house, garage conversions 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 stated for ADUs. Junior ADU: required, 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 | One 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 | 30 days or more. | No guarantee: cities may require rentals of more than 30 days, and junior ADUs can't be short-term rentals. |
- Hillside Performance Standards apply on slopes.
- The entrance can't face the street; colors and materials must match the house.
Where local rules conflict with state law, state law controls. Sources: Simi Valley Municipal Code § 9-44.160 (Ord. 1349, 2023) · HCD findings (Oct 29, 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 |
|---|---|---|---|
| Junior ADU (JADU) | too few to say | 4 | |
| Unclassified | 206 | 148 – 355 | 76 |
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
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 Simi Valley? Feature your business on this page.
Questions about ADUs in Simi Valley
How many ADUs have been permitted in Simi Valley?
Public records show 566 ADU permits in Simi Valley from 2018 through 2025. 192 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 Simi Valley?
Among the 80 ADU permits in Simi Valley with both dates recorded, half were issued within 211 days of the application; the middle half took 150 to 355 days. That includes plan-check corrections and resubmittals, not just the review itself.
Can I build an ADU on my property in Simi Valley?
California law allows ADUs on most lots with a house, including in Simi Valley, 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 Simi Valley?
Apply with the City of Simi Valley's Planning Division, which publishes an ADU guide. 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.