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Local ADU Rules

City of Sonoma

Last Updated September 13, 2024

ADU Contact:

Kristina Tierny, Associate Planner, ktierney@sonomacity.org

Standards	Details
Zones allowed	Any residential
Lot Restrictions	Lot coverage and floor area ratio standards, as required by underlying zoning, must be met. No application of FAR or site coverage standards requirements may require the ADU to be less than 800 square feet.
Minimum Lot Size	None.
Min/Max ADU Size	Detached and Attached: Maximum of 850 square feet for studio or 1 bedroom; can be up to 1,000 square feet if 2 bedrooms.
ADU Building Height	Detached single-story: 16 feet. Detached two-story: 25 feet, with one-story walls not exceeding 12 feet and second-story walls not exceeding 20 feet. Attached: maximum height allowed by the underlying zoning.
Setbacks	Side: 4 feet. Rear: 4 feet. Front: same as the underlying zoning.
Parking Requirements	Possibly, according to local zoning.
Owner Occupancy	Required only for Junior ADUs.
Sample fees from recent permits	$3,113.54 for conversion of garage to ADU. *Fees are specific to each project and will vary. Fees change regularly. These are provided as examples only.
Other requirements	Number of ADUs/JADUs allowed on single-family lot: One ADU or one JADU. One ADU and one JADU is allowed if the ADU is a detached structure. Number of ADUs allowed on mixed use or multi-family lot: At least one converted ADU, up to 25% of existing multi-family units. Up to 2 detached ADUs. JADUs must be created from existing interior space within an existing dwelling unit or an attached garage. Primary residence or JADU must be owner occupied.
Process	Approval of a Building Permit and ministerial approval of an ADU Permit. If an ADU or JADU meets these requirements only a Building Permit is required: 1. Interior Conversion: is either within the space of a proposed or existing single-family dwelling; or within the existing space of an accessory structure. has independent exterior access. side and rear setbacks which meet building and fire codes. 2. New Detached ADU: The side and rear yard setbacks are at least four feet. The total floor area is 800 square feet or smaller. The peak height above grade is 16 feet or less. Disclaimer: standards and process may vary. Consultation with the contact is recommended before starting any project.
Exceptions	1.ADUs and JADUs that are within the existing space of a single-family dwelling or within the existing space of an accessory structure that may be expanded by no more than 150 sq. ft. to accommodate ingress and egress. 2.Detached ADUs with a maximum floor area of 800 sq. ft., a maximum height of 16 feet, and is at least 4 feet from the side and rear lot lines. 3.Converted ADUs on multifamily lots 4.Detached ADUs on multifamily lots with a maximum total floor area of 800 square feet and are at least 4 feet from the side and rear lot lines.

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