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Local ADU Rules

San Anselmo

Last Updated May 21, 2025

ADU Contact:

Sarah Price or Elise Semonian planning@townofsananselmo.org
(415) 578-0112

Standards	Details
Zones allowed	Any that allow for single family and multifamily development.
Lot Restrictions	None.
Minimum Lot Size
Min/Max ADU Size	Minimum size: minimum necessary to comply with applicable building codes Maximum size: 850 square feet in floor area 1,000 square feet for a unit that provides 2 bedrooms Attached ADU floor area not to exceed 50% of the existing primary dwelling, but can be at least 800 square feet. Units up to 1,200 sq. ft. may be allowed with approval. One ADU and one JADU allowed on each single-family property. Also allowed on multifamily properties under state law. Up to two bedrooms. Additional bedrooms may be allowed with approval.
ADU Building Height	Detached ADU: up to 16 feet ADUs constructed in Special Flood Hazard Areas on the adopted Town Flood Insurance Rate Map: up to 14 feet measured from the Base Flood Elevation plus one (1) foot of freeboard, or sixteen (16) feet in overall building height, whichever is taller. ADU wall heights: 10 feet within the standard (non-ADU) setback areas required for the zoning district
Setbacks	None for conversions of existing living area or structure and 4-foot side and rear setbacks for new construction as per state law. Exceptions to setback requirements may be granted with approval. Side and rear setbacks must meet fire safety requirements.
Parking Requirements	One parking space per ADU unless 1) within ½ mile of transit , 2) is part of the proposed or existing primary residence or an accessory structure, 3) when on-street parking permits are required but not offered to ADU occupant; or 4) if car share within one block, then none required. Tandem parking and parking in setbacks are both allowed. An Exception from the parking space requirement may be granted.
Owner Occupancy	Not required for ADU or primary residence. Required for JADU.
Sample fees from recent permits	$5,381.91 ($100,000 valuation – includes $1000 road bond) $6256.68 ($120,000 valuation – includes $1200 road bond) Fees are based on valuation, please see our fee estimator: http://sananselmo.trakit.net/etrakit/feeestimatesummary.aspx Fees are specific to each project and will vary. Fees change regularly. These are provided as examples only.
Other requirements	An ADU shall include separate exterior access from the primary dwelling unit and may include an interior connection. The applicant must receive all discretionary permits before applying for a building permit (such as a tree permit or special watercourse permit). Fire sprinklers are needed if required for primary residence. The following standards apply to ADUs located within the required side and rear setbacks for the district in which the unit is located: The ADU entrance shall minimize noise and privacy impacts for neighbors by facing the entrance towards the interior of the lot and/or away from neighboring development, unless the accessory dwelling unit is directly accessible from an alley, public path, or public streetpublic path. Wall heights shall be limited to ten (10) feet.
Process	Projects that meet planning standards apply for a building permit with the Building Department and the Town will act on complete applications within 60 days. Projects requesting conditional use permits or variances need to apply to the Planning Department for a public hearing. It takes 2-6 months to get through the public hearing process. Disclaimer: standards and process may vary. Consultation with the contact is recommended before starting any project.
Exceptions	Exceptions to most standards may be granted with approval of a Conditional Use Permit. Variances may also be requested.

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