Getting an ADU permitted in Simi Valley
How an ADU permit works in Simi Valley: Building & Safety, the 60-day approve-or-deny rule, HCD's 19 findings on Ordinance 1349, and Ordinance 1373.
ADU permits in Simi Valley go through the City of Simi Valley Building & Safety Division, not Ventura County. Once your application is complete, state law gives the City 60 days to approve or deny it when a house already exists on the lot. If it does neither, the application is deemed approved.
What makes Simi Valley unusual is that its local ADU rules were rewritten in 2026 after the state found them out of compliance. Knowing which rules changed keeps you from designing around a limit that no longer applies.
The permit path, step by step
Most ADUs are approved ministerially, meaning no public hearing and no discretionary review, as long as the plans meet objective standards.
| Step | What happens | Notes |
|---|---|---|
| 1. Site review | Lot, utilities, slope, fire zone and trees checked | Optional City pre-application review: $438.33 |
| 2. Design | Plans, structural and energy calculations | Soils report on some hillside pads |
| 3. Submit | Application to City of Simi Valley Building & Safety | Plan check fee due at submittal |
| 4. Decision | Approve or deny within 60 days of a complete application | Gov Code 66317; deemed approved if the City misses it |
| 5. Corrections | A denial must list every deficiency and how to fix it | A resubmittal restarts the 60 days |
| 6. Build | Inspections at each stage | Inspection fee is part of the ADU fee line |
| 7. Final | Final inspection and occupancy sign-off | Then the unit can be rented or lived in |
What HCD told Simi Valley to change
On October 29, 2025, HCD sent the City 19 findings that Ordinance No. 1349 (adopted June 5, 2023) did not comply with state ADU law, with a response due November 28, 2025. The ones that matter most to a single-family homeowner:
- The ordinance cited Government Code 65852.2, which was repealed in 2024; ADU law now lives in Government Code 66310 to 66342.
- The City must approve or deny within 60 days, not merely 'act on' an application.
- No 6-foot separation can be required around a streamlined detached ADU beyond fire and safety rules.
- Garages cannot be counted as living area.
- Unpermitted structures can be converted into ADUs unless they threaten health and safety and are affected by the work.
- Outside-stair setbacks of 18 feet rear and 8 feet side cannot be applied to required ADU stairs.
- Subjective rules, like keeping the entrance off the street 'if possible', are not allowed.
Ordinance 1373 and what is still unsettled
A replacement ordinance, No. 1373, was reported adopted in July 2026 to update the ADU rules for state law; a second-reading ordinance normally takes effect 30 days after adoption (Gov Code 36937). The adopted text was not published online when this page was written, and cities submit adopted ADU ordinances to HCD for review, so any Ordinance 1349 figure you find online, including the 6-foot separation and the 50 percent attached cap, should be treated as superseded.
Practical rule: design to the state floors in Government Code 66321 and 66323, then confirm the City's current standards at the counter or in plan check. State law wins where the two conflict.
Questions homeowners ask
Who issues ADU permits in Simi Valley, the City or Ventura County?
The City of Simi Valley Building & Safety Division, for every address inside Simi Valley city limits. Applying to the county by mistake is a common lost week.
How long does Simi Valley take to approve an ADU?
The legal limit is 60 days from a complete application to approve or deny when a house already exists on the lot. A denial must include a full set of comments, and a corrected resubmittal starts a new 60-day clock.
Can I pay to speed up plan check?
The City's FY2024-25 schedule offers an expedited single-cycle plan check at double the plan check fee. Whether it is available for your project is the City's call.
Do I need a public hearing for an ADU?
No. ADUs that meet objective standards are approved without discretionary review or a hearing. Your neighbors are not asked to approve it.
Which law should my plans cite?
Government Code sections 66310 to 66342. The old section 65852.2 was repealed and its contents moved in 2024; HCD's first finding against Simi Valley's ordinance was that it still cited the old sections.
Sources
Facts on this page last verified: .
- HCD findings on Simi Valley ADU Ordinance No. 1349, October 29, 2025: https://www.hcd.ca.gov/sites/default/files/docs/policy-and-research/ordinance-review-letters/simi-valley-adu-findings-102925.pdf (2026-10-05)
- California Government Code section 66317 (60-day approve or deny): https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV§ionNum=66317. (2026-10-05)
- Ordinance 1373 (reported adopted July 2026): the adopted text was not published online when this page was written. Confirm current local ADU standards with City of Simi Valley Building & Safety: https://www.simivalley.org/departments/environmental-services/building-safety-division/online-permit-submittal-instructions (2026-10-05)
- City of Simi Valley Summary of Service Charges, effective July 1, 2024 (FY2024-25): https://simivalleylibrary.org/wp-content/uploads/2025/02/CityofSimiValley_FeeSchedule2025.pdf (2026-10-05)
- HCD ADU Handbook, updated for law in effect January 1, 2026: https://www.hcd.ca.gov/sites/default/files/docs/policy-and-research/adu-handbook-update.pdf (2026-10-05)
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