Accessory Dwelling Units (ADUs) & Junior ADUs (JADU)

The ADU rules apply to any property that is in a zoning district that allows residential use and has either existing or proposed dwelling units. For example, the Commercial/Office zoning district (C/O) is a commercial district that allows multifamily use under certain circumstances so the rules would apply to an existing or proposed residential use in the C/O district. 

There is a minimum size of 150 square feet for ADUs and JADUs. ADUs must include kitchen, sleeping, and bathroom facilities; a JADU may share eating and bathroom facilities with the primary dwelling provided there is an internal connection. 

If you are adding square footage onto an existing structure to create an attached ADU, the square footage of the ADU cannot exceed 50% of the square footage of the main residence or 1,000 square feet, whichever is less; however, an ADU of up to 800 square feet is always allowed.  

Examples:  

• 2,200 square-foot main residence à 1,000 square-foot ADU allowed 
• 1,800 square-foot main residence: à 900 square-foot ADU allowed  
• 1,500 square-foot main residence: à 800 square-foot ADU allowed  
• 1,000 square-foot main residence: à 800 square-foot ADU allowed 

If you are building a new structure that is separate from the existing main residence to create a detached ADU, the square footage of the ADU cannot exceed 1,000 square feet.  

If you are converting existing space into an ADU, there is no limit on the size of the ADU.  

If you are constructing a JADU through internal conversion of a single-family residence, the square footage of the JADU cannot exceed 500 square feet.  

Regardless of lot coverage, floor area ratio, natural state, setback, and other standards you are allowed an ADU of up to 800 square feet provided it has the minimum 4-foot rear and side yard setback and complies with the maximum height limits. 

No additional setback is required for an ADU if constructed in the same footprint and with the same dimensions (including height) as the existing structure. An expansion of no more than 150 square feet beyond the existing dimensions can be allowed for ingress and egress purposes only. 

Properties with a Single-family residence may have the following: 

• One detached ADU (new construction or conversion).
• One attached ADU (new construction or conversion).
• One JADU (conversion).
• A combination of one detached or attached ADU, one JADU, and one conversion ADU.

ADUs may either be created through conversion of non-habitable space (e.g. basement, laundry room, or storage areas) within the multi-family structure or by conversion of existing accessory structures or new construction of detached structures. No JADUs are permitted. 

• Within Existing Main Structure: At least one (1) ADU is allowed up to a maximum of twenty-five percent (25%) of the existing multifamily dwelling units. 

• Detached: A maximum of two ADUs are allowed. 

When a garage, carport, or covered parking structure is demolished in conjunction with the construction of an ADU or converted to an ADU, replacement off-street parking is not required. 

One parking space is required per ADU, unless: 

• The ADU is located within one-half (½) mile walking distance of public transit. 

• The ADU is located within an architecturally and historically significant district. 

• The ADU is created through conversion of existing space (either in the main structure or a detached structure). 

• On-street parking permits are required but not offered to the occupant of the ADU. 

• There is a car share vehicle located within one (1) block of the ADU at the time the application is filed with the City. 

• A permit application for an accessory dwelling unit is submitted with a permit application to create a new single-family dwelling or a new multifamily dwelling on the same lot. 

No parking is required for JADUs. 

No off-street parking is required for an ADU that is located within one-half mile walking distance of public transit.  “Public transit” means a location, including, but not limited to, a bus stop or train station, where the public may access buses, trains, subways, and other forms of transportation that charge set fares, run on fixed routes, and are available to the public. 

The city has this map that shows the areas we know are within half a mile of transit. Follow this up with a snap shot of walking distance via Google Maps or other map app. If our map shows you are outside the half mile radius but you have updated information that shows you are within half a mile of transit, please submit supporting documentation to the City to review. This can be a map showing where the public transit is located and the walking path highlighted with distances located. Staff will evaluate the documents for accuracy. 

Fire sprinklers cannot be required in an ADU if sprinklers are not required for the primary residence. Construction of an ADU does cannot trigger a requirement that fire sprinklers be installed in the proposed or existing primary dwelling. 

Unpermitted JADUs and ADUs follow the same building permit review process and California Building Code requirements as new construction, very similar to additions or remodels. Attached ADUs will need to have fire rated separations, egress, and separate electrical and mechanical systems per California Building Codes.  The application for building permits should include plans for review and payment of permit fees. Once the permit application is reviewed and issued, then inspections will need to be scheduled and final inspection passed. 

The planning fees associated with the construction of an ADU/JADU are included in the building permit application. The planning fee is based on the project’s total cost valuation. Additional flat rate fees include electrical, plumbing, and mechanical permit fees. The following fees are waived for ADU builds less than 750 sq feet: impact fees, general plan maintenance, street maintenance, and bedroom taxes. For more building permit information please email: building@cityofsanrafael.org . 

CC&Rs that either effectively prohibit or unreasonably restrict the construction or use of an ADU or JADU on a lot zoned for single-family residential use are void and unenforceable. 

Yes, attached garage are considered eligible spaces to be converted into a JADU. Other spaces include a master bedroom, or other space within the main residence.  

No, the JADU cannot be sold separate from the primary dwelling. 

The method of construction of any proposed ADU shall be reviewed under the same Building Permit application by the Building Department, but will be reviewed separately by the Planning Department. Note that all ADUs, no matter the type, must have a permanent foundation and permanent utilities.