California ADU rules · Ventura County
Can I Build an ADU in Simi Valley?
Yes — you can build an ADU in Simi Valley. California's statewide ADU law requires every city, including Simi Valley, to approve a qualifying accessory dwelling unit by right, plus a junior ADU (JADU) on a single-family lot. What varies city to city are the local specifics below.
Can you build one?
ADUs allowed
CA state lawYes — by right
ADUs and JADUs are allowed by right in all residential and mixed-use zones; ministerial approval, no hearing.
Units on a single-family lot
Local rule1 ADU (attached or detached) + 1 JADU; if both, ADU must be detached and limited to 800 sq ft
If both an ADU and JADU are built, the ADU must be detached and is capped at 800 sq ft.
Units on a multifamily lot
Local ruleup to 2 detached ADUs per lot + conversions of non-livable space up to 25% of existing units (minimum 1)
Detached ADUs on multifamily lots are capped at 2 per lot.
Junior ADU (JADU)
CA state lawAllowed
Up to 500 sq ft, within the walls of an existing single-family home (single-family lots only).
Size & height
Max detached ADU size
Local rule1,000 sq ft
Parcels ≤8,000 sq ft: 1,000 sq ft max; parcels >8,000 sq ft: 1,200 sq ft max. If both ADU and JADU, ADU is limited to 800 sq ft.
Max attached ADU size
Local rule50% of primary or 800 sq ft (whichever is larger), up to 1,000 sq ft max
Attached ADUs cannot exceed 1,000 sq ft.
Guaranteed minimum size
CA state law800 sq ft
An 800 sq ft ADU must be allowed regardless of FAR/lot-coverage caps; a city also cannot cap an attached ADU below 850 sq ft (1,000 for 2+ bedrooms).
Max JADU size
CA state law500 sq ft
Max height
Local rule18 ft
Detached ADUs: 18 ft (one story), up to 20 ft within ½ mile of a major transit stop or high-quality transit corridor. Attached ADUs: up to 25 ft or the primary dwelling's height limit, whichever is lower.
Setbacks
Side setback
Local rule4 ft
4 ft minimum for new construction ADUs; attached ADUs >25 ft height require 10 ft side setback.
Rear setback
Local rule4 ft
4 ft minimum for new construction ADUs; attached ADUs >25 ft height require 20 ft rear setback.
Front setback
Local rule20 ft minimum for new construction ADUs; attached ADUs >25 ft height require 20 ft front setback
Front setback for ADUs is 20 ft minimum.
Separation from main house
Local rule6 ft
Detached ADUs must be at least 6 ft from the main dwelling and other structures (10 ft if second ADU with SB9 unit).
Parking
Parking required
Local ruleUp to 1 space
One parking space per ADU, with multiple exemptions.
Transit parking exemption
CA state lawYes — no parking required near transit & for conversions
No parking may be required within ½ mi walking distance of transit, in a historic district, for an ADU within an existing structure, within one block of car-share, or in certain permit-parking areas.
Garage-conversion replacement parking
Local ruleNot required
No replacement parking required for garage/carport/covered parking conversion.
Approval, timeline & cost
Approval path
CA state lawMinisterial (by right)
No public hearing or discretionary design review for a qualifying ADU.
Approval timeline
CA state law60 days
The agency must act within 60 days of a complete application — and the ADU is deemed approved if it does not.
Owner-occupancy
Local ruleOnly for a JADU
No owner-occupancy for ADUs; JADUs require owner to occupy either the JADU or primary dwelling.
Impact-fee waiver
CA state lawWaived under 750 sq ft
An ADU of 750 sq ft or less pays no impact fees (the 750 sq ft threshold itself is exempt under § 66311.5); larger ADUs pay fees proportional to the primary dwelling. JADUs (≤ 500 sq ft) are exempt.
Permits required
Local ruleZoning clearance, Building permit
Both zoning clearance (ministerial) and building permit are required.
Simi Valley-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
Very High Fire Hazard Severity Zone (VHFHSZ)
ADUs in VHFHSZ must meet high fire construction standards; no variances allowed.
Hillside Areas
ADUs in hillside areas (SVMC Ch. 9-32) limited to 800 sq ft.
Historic Properties
ADUs not permitted on historic properties or parcels listed as historic resources.
Simi Valley imposes a 1,000 sq ft detached ADU cap on parcels ≤8,000 sq ft and 1,200 sq ft on larger lots, with a unique 800 sq ft cap for ADUs when a JADU is also built. Hillside and historic properties face additional restrictions, and front setbacks for ADUs are 20 ft minimum.
Frequently asked questions
Can I build an ADU in Simi Valley?
Yes. California's statewide ADU law requires Simi Valley to approve a qualifying accessory dwelling unit ministerial (by right), plus a junior ADU (JADU) on a single-family lot.
How big can an ADU be in Simi Valley?
A detached ADU of at least 1,000 sq ft must be allowed, and an ADU of 800 sq ft can never be zoned out by floor-area or lot-coverage limits. A JADU can be up to 500 sq ft.
What are the setback requirements for an ADU in Simi Valley?
Side and rear setbacks are limited to 4 ft. 20 ft minimum for new construction ADUs; attached ADUs >25 ft height require 20 ft front setback.
Is parking required for an ADU in Simi Valley?
Up to 1 space. No parking can be required within ½ mile of transit, for conversions, or for units inside the primary home. When a garage is converted, replacement parking is not required.
How long does ADU approval take in Simi Valley?
A complete application must be acted on within 60 days, with ministerial (by right) — no public hearing or discretionary design review for a qualifying ADU.
Do I have to live on the property to build an ADU in Simi Valley?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- SVMC §9-44.160 (as amended through 2023)
- SVMC §9-44.160(B), Table 4-4
- SVMC §9-44.160(F)(4), Table 4-4
- SVMC §9-44.160(E)(1)-(2)
- SVMC Table 4-5; §9-44.160(E)-(F)
- SVMC Table 4-5, Table 4-6; §9-44.160(E)-(F)
- SVMC §9-44.160(F)(3)
- SVMC Table 4-5; §9-44.160(C)
- SVMC §9-44.160(E)(4)
- SVMC §9-44.160(A)(6), (D)(2)
- SVMC §9-44.160(A)(3)
- SVMC §9-44.160(A)(5)
- SVMC §9-44.160(A)(11)
- SVMC §9-44.160(H)
- Cal. Gov. Code §§ 66310–66342 (ADU Law)
- HCD 2025 Accessory Dwelling Unit Handbook
- Cal. Gov. Code § 66317 (ministerial approval, 60-day deadline)
- Cal. Gov. Code § 66333 (junior ADUs)
- Cal. Gov. Code § 66321 (size minimums & height)
- Cal. Gov. Code § 66322 (ADU parking; § 66334 covers JADU parking)
- Cal. Gov. Code § 66311.5 (impact fees: none for an ADU ≤ 750 sq ft or JADU ≤ 500 sq ft)
Last updated 2026-06-25. This is an AI-assisted summary of Simi Valley's ADU rules, drawn from its published ordinance and California ADU law — general information, not legal advice, and it may be incomplete or out of date. Verify the controlling rule for your specific parcel with Simi Valley Planning before relying on it.
Will an ADU work on your Simi Valley lot?
Ask GoCodebook about your address and get the size, setback, parking and permit rules that actually apply to your parcel — with the exact citation.
Check my parcel free