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Local ADU Rules

Unincorporated Marin County

Last Updated May 21, 2025

ADU Contact:

Jillian Zeiger, jzeiger@marincounty.org

Standards	Details
Zones allowed	All except Industrial Planned.
Lot Restrictions	See zoning restrictions, otherwise, none.
Minimum Lot Size
Min/Max ADU Size	JADU: >500 square feet ADU Attached: shall not exceed 50% of existing residences floor area ADU Detached: maximum ADU Size 1,200 SF 1 JADU and 1 ADU, unless multifamily. If multi-family two detached or up to 25% of existing units. ADU must contain at least 2 bedrooms if over 1,000 square feet.
ADU Building Height	New, detached ADU generally, up to 16 feet. If attached to the primary structure the ADU should comply with height standards of the primary structure.
Setbacks	Side and rear setback of 4’ for any new ADU at or under 800 square feet 16 feet in height, front setback should comply with standards of the primary structure. No setback requirements if converting a legal garage. Side and rear setbacks must meet fire safety requirements.
Parking Requirements	No parking requirements for JADUs. Unless exempted by state law, 1 space assigned to a studio or one-bedroom Accessory Dwelling Unit or 2 spaces assigned to a two-or-more-bedroom Accessory Dwelling Unit.
Owner Occupancy	Required for JADUs.
Sample fees from recent permits	New structure, 800 square feet, not septic or in the coastal zone: $11,985 Addition to an existing structure, 600 square feet, not septic or in the coastal zone: $8,175 *Fees are specific to each project and will vary. Fees change regularly. These are provided as examples only.
Other requirements	Deed restriction for applicants who receive fee waivers. Deed restrictions on JADUs- they cannot be sold separately from the single-family residence. Fire Sprinklers: Needed if required for primary residence.
Process	Apply for ministerial planning permit, in some cases JADU go straight to building permit. Disclaimer: standards and process may vary. Consultation with the contact is recommended before starting any project.
Exceptions	Coastal Zone

Wondering what you can build?

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