ADU rules in Thousand Oaks

Detached ADUs are a permitted (P) accessory use in the R-A, R-E, R-O, R-1, R-2, R-3, RPD and HPD zones, and Article 45 allows them on any single-family-zoned lot (R-A, R-E, R-O, R-1, RPD, HPD or a specific plan) with one existing or proposed home. The city must ministerially approve a new detached unit of up to 800 sq ft with 4 ft side and rear setbacks, and each lot may instead use its one local-standards ADU (detached up to 1,000 sq ft), which the code counts against the state-mandated allowance. Lots in the R-2, R-3, RPD and MU zones are limited to the state-mandated units of Sec. 9-4.4511, which include up to eight detached ADUs (capped at the number of existing units) beside an existing multifamily building, or two beside a proposed one. HCD's 6-1-2026 findings call the counting rule and the multifamily-zone limit unlawful because at least one Gov. Code 66314 unit must be allowed on top of every 66323 unit, and Sec. 9-4.4502(b) lets the Government Code prevail. The local text bars ADUs on natural slopes over 25 percent and limits them near protected ridgelines and oaks, and the TPD mobile home park zone does not list ADUs.

An ADU may be converted from space inside an existing or proposed home or an existing accessory structure (with up to 150 sq ft added for access), or built as an attached addition under the local standards, which require at least 10 ft of shared wall with the house, a full kitchen and bathroom separate from the main home, an exterior entrance on a different wall face than the main entry and no internal connection. Second-story ADUs are allowed with interior stairs only; HCD's 6-1-2026 findings say the exterior-stair ban is unlawful where stairs are needed to use the 25 ft attached height allowance. One JADU of up to 500 sq ft may be created only by converting space within the walls of a single-family home (an attached garage counts) and may sit beside a conversion ADU under Sec. 9-4.4511(a)(1). On multifamily lots, at least one ADU and up to 25 percent of the existing unit count may be created in non-livable space such as storage rooms, attics, basements or garages.

A local-standards detached ADU may have up to 1,000 sq ft of interior livable space, and an ADU converted within or attached to the house up to 850 sq ft or 50 percent of the existing home's total floor area, whichever is greater; the minimum is an efficiency unit. The state-mandated detached unit is capped at 800 sq ft of interior livable space, detached units on multifamily lots carry no size cap, conversions approved under Gov. Code 66323(a)(1) are limited only by the existing or proposed space, plus up to 150 sq ft for access when an accessory structure is converted (HCD: conversions are not subject to unit size requirements), and a JADU may not exceed 500 sq ft. Heights are 16 ft for a detached ADU, 18 ft within a half mile of a major transit stop or high-quality transit corridor, plus 2 ft to match the main roof pitch, and 25 ft or the house's zone height limit, whichever is lower, for an attached ADU. A garage attached to a detached ADU is limited to 400 sq ft, patio covers and porches to 10 percent of the ADU's area (not counted), and an accessory structure attached to a detached ADU must fit within the ADU's size cap. Gov. Code 66321(b)(2) bars a maximum below 1,000 sq ft for a unit with more than one bedroom, so on a home under 2,000 sq ft a two-bedroom attached ADU may reach 1,000 sq ft despite the 850 sq ft or 50 percent text.

No owner-occupancy requirement applies to ADUs (Gov. Code 66315 forbids one), and the city ADU page confirms that an ADU and the house may be rented to different parties. For JADUs, Ord. 1747-NS limits the requirement to a JADU that shares sanitation facilities with the main home: the owner must then live in either the house or the JADU, and no requirement applies to a JADU with its own bathroom or to an owner that is a governmental agency, land trust or housing organization, matching Gov. Code 66333(b) as amended by AB 1154. The recorded JADU deed restriction (Sec. 9-4.4512(c)) still restates that rule and requires disclosure of it to future owners, which HCD's 6-1-2026 findings say exceeds the two items Gov. Code 66333(c) allows in a deed restriction. The city ADU page still says that any property with a JADU must be owner-occupied, a pre-2026 statement the code has superseded.

The code requires one off-street space for an ADU in addition to the house's parking; it may be covered or uncovered, in any setback and tandem on the driveway, and spaces lost when a garage or carport is converted or demolished for the ADU need not be replaced. No space is required when the ADU is within one-half mile walking distance of public transit, in an architecturally and historically significant historic district, part of the existing or proposed home or an accessory structure or converted from an existing structure, where on-street permits are required but not offered, within one block of a car-share vehicle, applied for together with a new home or multifamily building, or 500 sq ft of interior livable space or smaller. The local text does not exempt the state-mandated units of Sec. 9-4.4511, but Gov. Code 66323(b) bars any standard that section does not authorize (HCD's March 2026 handbook: no parking may be imposed on 66323 units) and Sec. 9-4.4502(b) lets state law prevail. Gov. Code 66314(d)(10)(A) caps ADU parking at one space per unit or per bedroom, whichever is less, and HCD reads a studio as adding no bedroom, so the one-space rule cannot bind a studio over 500 sq ft. In practice a space is owed only for a local-standards unit with a bedroom outside the exemptions, chiefly a detached unit over 800 sq ft (the code does not say whether an attached addition counts as 'part of' the home under (c)(3)); JADUs need no parking.

No ADU or JADU may be created without a building permit, and applications are reviewed ministerially, without discretionary review or a hearing: the Community Development Department decides completeness within 15 business days (and again within 15 business days of a resubmittal) and approves or denies a complete application within 60 days when a home already exists on the lot (an application filed with a new house may wait for the house permit). Denials must list every deficiency and how to cure it; an incompleteness or denial determination may be appealed within 10 calendar days to the Planning Commission, which decides ministerially without a public hearing within 60 business days, and its decision is final. The residential use matrix lists ADUs as P (no discretionary entitlement) in every residential zone except the TPD mobile home park zone. Applications go through the TO/24 online portal, and the Building Division's July 2026 completeness checklist requires Ventura County Fire Department fire-flow verification and 610B conditions before an application is deemed complete.

An ADU or JADU may be rented separately from the house but not for a term of 30 days or less, which rules out short-term rentals. For JADUs and state-exempt (66323) units that matches Gov. Code 66333(g) and 66323(e) (terms longer than 30 days); for a local-standards ADU it runs one day past Gov. Code 66315, which lets a city require only terms of 30 days or longer, and the city ADU page describes the rule as 'a minimum term of 30 days', so both texts are recorded while the codified Sec. 9-4.4506(b) states the operative rule. ADUs and JADUs may not be sold or conveyed separately from the house except under Gov. Code 66341 (qualified nonprofit affordable ownership), and the city has not opted into the Gov. Code 66342 ADU-condominium conveyance. The Municipal Code has no short-term rental permit program or rental registry; the 10 percent transient occupancy tax of Chapter 3-14 reaches hotel-type stays of 30 consecutive days or less.