Thousand Oaks ADU: Regulations, Costs & Permits

• Planning Division: reviews the ADU application. The city decides whether it's complete within 15 business days, and approves or denies it within 60 days when a home already exists.
• Building Division: issues ADU and JADU permits.
• Online: everything runs through TO/24, the city's virtual land use system, including plans, corrections, payments, and inspections.
• Appeals: incompleteness or denial decisions can be appealed within 10 days to the Planning Commission, which decides without a public hearing.

• Single-family lots: the state-guaranteed units plus one more ADU built to the city's standards.
• Attached or converted ADU: up to 850 sq ft or 50% of the home, whichever is greater. It must share at least 10 ft of wall with the house, with no interior connection, and its entrance must be on a different wall than the main entry.
• Detached ADU: up to 1,000 sq ft of living space, at least 6 ft from other buildings, and no breezeway to the house. An attached garage can be up to 400 sq ft, and covered porches and patios are capped at 10% of the ADU's size.
• Height: detached ADUs are 16 ft, or 18 ft plus 2 ft for roof pitch near major transit. Attached ADUs follow the house, up to 25 ft.
• Setbacks: 4 ft side and rear, and the house's front setback.

• Matching the house: attached and converted ADUs match the house's wall, roof, eave, window, and door materials and colors. Every ADU matches the house's main roof slope. A detached ADU uses at least one material and one color from the house.
• Privacy glass: windows within 10 ft of a neighboring home need privacy glass of at least 50% opacity.
• No roof decks or rooftop equipment: ground-mounted equipment has to sit outside the 4 ft setbacks.
• Second-story ADUs: no exterior stairs, the new floor steps back at least 2 ft from the wall below, and the facade needs at least two articulation features.
• Access: the ADU shares the main driveway unless you have alley access or a qualifying corner lot, and a walkway from the street to the ADU entrance is required.
• Garage conversions: the garage door is replaced with windows that match the house.

• Steep slopes: no ADU on or encroaching onto a natural slope steeper than 25%.
• Protected ridgelines: no new structure, grading, or native vegetation removal within 300 ft horizontally or 100 ft vertically of a protected ridgeline crest, unless that would block the minimum units state law guarantees. Then the ADU goes at the lowest possible elevation.
• Oak trees: an ADU can't be built, or graded for, inside a protected tree's zone unless that would block an 800 sq ft ADU. Then the tree can be encroached on or removed and replaced one for one with a 36-inch box coast live oak or valley oak, or with an in-lieu fee.
• Fire zones: Ventura County Fire adopted the state's 2025 fire hazard maps effective July 1, 2025. If your parcel spans more than one zone, the highest applies to the whole lot. Sprinklers are needed only if the house requires them.
• Septic: ADUs on septic need feasibility sign-off and a permit from the State Water Resources Control Board before the building permit, with a new septic application filed alongside the ADU.

• ADU Plans Gallery: the city's online gallery lists pre-approved and other designs from outside designers. You buy or license a plan and still submit a site-specific site plan.
• Legalizing: for ADUs built without permits before 2020, the city won't deny a permit over code noncompliance unless the unit is substandard, and won't charge impact or connection fees except where needed for health and safety.

• Building fees: the city says building plan check and permit fees have averaged $2,800 to $3,200 per ADU over the past three years, with a fixed Planning fee on top.
• Impact fees: none on ADUs under 750 sq ft of living space. Larger units pay in proportion to the house, and can include water and wastewater connection, traffic, school (Conejo Valley Unified), police, fire, and parks fees.
• Connections: an ADU isn't charged as a new use for connection fees unless it's built with a new house, but new ADUs do need their own utility connections. Conversions of an existing structure don't.
• Property tax: rises based on the ADU's added value only.

Newbury Park follows the same city ADU rules as the rest of Thousand Oaks. The main local difference is water: most of Newbury Park and western Thousand Oaks is served by California American Water, central Thousand Oaks by the city, eastern Thousand Oaks by California Water Service, and some areas by Camrosa. The city publishes a water provider map, and your provider handles meter and connection questions.

• Parking: one space (covered or uncovered, allowed in setbacks, tandem is fine), with the state exemptions plus a local one: no parking for ADUs of 500 sq ft or less. No replacement when you convert a garage.
• Rentals: more than 30 days. ADUs can't be sold separately.
• JADU: up to 500 sq ft inside the house or attached garage, with a recorded deed restriction. Owner occupancy is only required if it shares a bathroom with the house.

How big can an ADU be in Thousand Oaks?

A detached ADU can be up to 1,000 sq ft of living space. An attached ADU can be 850 sq ft or half the size of the home, whichever is greater.

What do ADU permits cost in Thousand Oaks?

The city reports building plan check and permit fees averaging $2,800 to $3,200 per ADU, plus a Planning fee. ADUs under 750 sq ft avoid impact fees.

Do Newbury Park ADUs follow different rules?

No. Newbury Park is part of Thousand Oaks and uses the same ADU code. Most of it gets water from California American Water rather than the city.

Can I build an ADU on a sloped lot in Thousand Oaks?

Not on a natural slope over 25%, and not within 300 ft of a protected ridgeline, unless that would block the minimum units state law guarantees.

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