California ADU rules · Ventura County
Can I Build an ADU in Thousand Oaks?
Yes — you can build an ADU in Thousand Oaks. California's statewide ADU law requires every city, including Thousand Oaks, 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
CA state law1 ADU + 1 JADU
At least one ADU and one JADU per single-family lot (a conversion ADU may also be possible).
Units on a multifamily lot
Local ruleconversions (>=1 or 25% of units) + up to 2 detached
Local cap of 2 detached ADUs per multifamily lot; state allows up to 8.
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 rule850 sq ft
Studio detached ADU max is 850 sq ft; 1,000 sq ft for 1-bedroom; 1,200 sq ft for 2+ bedrooms on lots ≥1 acre.
Max attached ADU size
Local rule850 sq ft or 50% of primary, whichever is greater
Local rule sets 850 sq ft or 50% of primary dwelling, whichever is greater.
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 rule16 ft
Detached ADU: 16 ft standard; 18 ft within ½ mile of transit or on multifamily lot; attached ADU: up to 25 ft or primary dwelling height limit.
Setbacks
Side setback
CA state law4 ft
A city cannot require more than 4 ft side or rear setback; conversions of existing structures are exempt.
Rear setback
CA state law4 ft
Front setback
CA state lawNo front setback may block the mandatory 800 sq ft / 16-ft / 4-ft-setback ADU; otherwise per base zone
Separation from main house
Local rule6 ft
Detached ADUs must be separated from any structure by at least 6 ft.
Parking
Parking required
Local ruleUp to 1 space
1 off-street space per ADU required unless exempt.
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
CA state lawNot required
When a garage/carport is demolished or converted to build an ADU, replacement parking cannot be required.
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
CA state lawOnly for a JADU
No owner-occupancy requirement for ADUs (the prior sunset was removed). A JADU may require owner-occupancy, principally where it shares sanitation with the main house.
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 ruleADU permit, Building permit
Both ADU permit and building permit required.
Thousand Oaks-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)
No ADU may be placed where it would require an adjacent property owner to provide defensible space per CA Fire Code Sec. 4907 (as amended by Ventura County Fire Protection District).
Hillside Slope >25%
No ADU allowed on slopes steeper than 25%.
Thousand Oaks limits detached ADUs to 850–1,200 sq ft depending on unit type and lot size, and allows only 2 detached ADUs on multifamily lots. Detached ADUs must be separated from other structures by at least 6 feet.
Frequently asked questions
Can I build an ADU in Thousand Oaks?
Yes. California's statewide ADU law requires Thousand Oaks 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 Thousand Oaks?
A detached ADU of at least 850 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 Thousand Oaks?
Side and rear setbacks are limited to 4 ft. No front setback may block the mandatory 800 sq ft / 16-ft / 4-ft-setback ADU; otherwise per base zone.
Is parking required for an ADU in Thousand Oaks?
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 Thousand Oaks?
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 Thousand Oaks?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Thousand Oaks Municipal Code, Article 4, Division 4, Sections 9-4.4500 et seq. (Ord. 1732-NS, effective November 22, 2024; amendments through April 25, 2025)
- Sec. 9-4.4513
- Sec. 9-4.4506(c)(1)
- Sec. 9-4.4506(b)(1)
- Sec. 9-4.4506(c)(3)-(6)
- Sec. 9-4.4506(c)(7)
- Sec. 9-4.4508(a)-(c)
- Sec. 9-4.4503(a)
- Sec. 9-4.4505(c)(2)
- Sec. 9-4.4505(c)(1)
- 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 § 66323 (by-right ADU/JADU, 800 sq ft, 4-ft setbacks)
- 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 § 66314 (local ordinance standards)
- Cal. Gov. Code § 66315 (owner-occupancy)
- Cal. Gov. Code § 66311.5 (impact fees: none for an ADU ≤ 750 sq ft or JADU ≤ 500 sq ft)
Last updated April 25, 2025. This is an AI-assisted summary of Thousand Oaks'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 Thousand Oaks Planning before relying on it.
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