Please note:  City Hall and most departments/facilities will be closed from December 23rd through January 2nd. We will resume all services on Tuesday, January 3, 2023.

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

What is an Accessory Dwelling Unit?
An Accessory Dwelling Unit (aka, “second unit,” “in-law unit,” or “granny unit”) is an additional dwelling located on the same lot as a single-family or multi-family development. An Accessory Dwelling Unit may be attached to the primary residence, detached from the primary residence, or contained within an existing residence or accessory structure. A Junior Accessory Dwelling Unit (JADU) is a unit that is no more than 500 square feet and contained entirely within the single-family structure.

What is the Review Process?
In order to make the review process as efficient as possible, accessory dwelling unit (ADU) and junior accessory dwelling units (JADU) applications will now be submitted to the Building Division as a building permit. Prior to submitting to building, please review the Data Sheet/ Checklist for Accessory Dwelling Units and JADUs with a Planner. The Planning Division will still do an official required ministerial review during the Building Permit Plan Check timeframe and the ADU review fee ($300) will be charged in addition to building permit fees through the building permit.

ADU Ordinance

On December 6, 2021, the City of San Rafael adopted an ADU ordinance that establishes local regulations consistent with changes in state law regarding ADUs and JADUs. The ADU ordinance makes it easier to develop an ADU and streamlines the permit review process, which further encourages and facilitates ADU start-ups as a source of affordable housing.

The changes are codified in 14.16.285 – Accessory dwelling units (ADUs).

The Ordinance regulates ADUs and JADUs as follows:

Size of Unit (Floor Area).

  • ADUs would need to have a minimum size of 150 square feet (known as an efficiency unit);
  • Attached ADUs would have a maximum floor area of 1,000 square feet or 50% of the existing residence, whichever is less;
  • Detached ADUs would have a maximum floor area of 1,000 square feet;
  • There is no maximum size limit for ADUs that involve the conversion of an existing detached structure;
  • There is no maximum size limit for an ADU created from internal conversion of portions of an existing primary residence;
  • JADUs may be no less than 150 square feet and no more than 500 square feet.

Required Setbacks.

  • Maximum rear and side yard setbacks of a new or expanded ADU are 4 feet;
  • No additional setbacks are required for internal conversions;
  • Front yard setback will be the same as required for the primary residence.

Maximum Height:

  • Up to 16 feet high if within 4 feet of the rear or side yard;
  • Height limited in the Eichler-Alliance overlay district may not exceed a height of 17 feet;
  • Accessory dwelling units complying with the development standards established for the primary residence are subject to the same height limit established by the district governing the property.

Additional Frequently Asked Questions

The rules apply to properties that are in a zoning district that allows residential use. For example, the Commercial/Office zoning district (C/O) is a commercial district but it does allow multifamily use under certain circumstances so the rules would apply to an existing residential use in the C/O district.

Fire sprinklers cannot be required in an ADU if sprinklers are not required for the primary residence. However, if the addition of the ADU incorporates a remodel of more than 50% of the main residence then sprinklers will be triggered for both the main residence and the ADU.

In a single-family residence: The floor area of the ADU should have at minimum a combined living, eating and sleeping room not less than 70 square feet. For a multifamily residence, an ADU should contain at minimum combined living, eating and sleeping room not less than 150 square feet. In both cases, any additional habitable rooms should be a min of 70 square feet and not less than 7 feet in any direction.

There is no square footage limit for existing space. If you are adding square footage to create an ADU, the square footage of the unit cannot exceed 50% of the main residence. A detached ADU cannot exceed 1,000 square feet.


  • Within an existing or proposed single-family home: One ADU or one junior ADU per lot if exterior access is available; and side and rear setbacks are sufficient for fire and safety.
  • Detached: One detached, new construction ADU can be added to a property. This can be in addition to a JADU.

Regardless of lot coverage, floor area ratio, natural space and other standards the City must permit at least an 800 sq. ft. ADU that is up to 16 feet tall with at least a 4-foot setback.

When ADUs are created through the conversion of a garage, carport or covered parking structure, replacement off-street parking is not required.


  • Within Existing Structure: At least one ADU within portions of existing multifamily dwelling structures that are not as livable space if each unit complies with state building standards. The number of ADUs shall allow up to 25% of the existing multifamily dwelling units. No JADUs allowed
  • Detached: Not more than two ADUs that are located on a lot that has an existing multifamily dwelling but are detached from the dwelling and are subject to a height limit of 16 feet and four-foot rear and side setbacks.

No additional setback is required for ADU if constructed in the same location and with the same dimensions 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.

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.

The City cannot require parking be provided for an accessory dwelling unit 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. 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.

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