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Local ADU Rules

City of St. Helena

Last Updated August 30, 2024

ADU Contact:

Maya DeRosa, mderosa@cityofsthelena.org
Aaron Hecock, AHecock@cityofsthelena.org

Standards	Details
Zones allowed	All residential
Lot Restrictions	None.
Minimum Lot Size	None.
Min/Max ADU Size	Current code compliant with state law. The maximum size of a detached or attached ADU is 850 square feet for a studio or one-bedroom unit and 1,000 square feet for a unit with two bedrooms. No more than two bedrooms are allowed. Attached: Not to exceed 50 percent of the existing living area with a maximum increase of 1,000 square feet. JADUs: Maximum of 500 square feet.
ADU Building Height	Detached: Detached ADUs are generally limited to 16 feet. If an ADU is built on a lot within one-half mile of a major transit stop or a high quality transit corridor it may be built up to 18 feet, or up to 20 feet to align the roof pitches of the ADU and the primary dwelling unit. A detached ADU may be built up to 18 feet if it is created on a lot with an existing or proposed multifamily dwelling unit with more than one story above grade. Attached: Attached ADUs are limited to 25 feet, or the height limit of the underlying zoning. An Attached ADU may not exceed two stories.
Setbacks	4 feet side and rear lot line setback, and 20 feet front lot line setback.
Parking Requirements	Same as the state requirements. Parking removed from the primary dwelling such as a garage, carport, or covered parking structure, need not be replaced as off-street parking.
Owner Occupancy	ADU: ADUs built after January 1, 2020, but before January 1, 2025, are not subject to owner occupancy requirements. ADUs created on or after January 1, 2025, are subject to an owner occupancy requirement. JADU: As required by state law, all JADUs are subject to an owner occupancy requirement.
Sample fees from recent permits	624 SF Detached ADU, New Construction. Total: $16,833.49 (Includes $2,172.52 SHUSD Fee) *Fees are specific to each project and will vary. Fees change regularly. These are provided as examples only.
Other requirements	Any existing structure can be converted regardless of setbacks.
Process	Approved through building permit with 30 to 60 day process. Disclaimer: standards and process may vary. Consultation with the contact is recommended before starting any project.
Exceptions	Use permit process.

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