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What is a Junior Second Unit?

Junior Second Unit means an additional, independent living unit which is created through the conversion of an existing bedroom within an existing single-family residential dwelling as part of the single-family use, and subject to defined standards in Section 14.16.286 of the Zoning Code. A Junior Second Unit may be proposed as an alternative to (in lieu of) a Second Dwelling Unit, and subject to similar design and occupancy limitations, but is distinguished from a Second Dwelling Unit as follows:

  • A Junior Second Unit must be established from conversion of an existing bedroom(s) within the existing single family residential dwelling floor area.
  • A Junior Second Unit cannot be created as a direct result of a building addition.
  • A Junior Second Unit is smaller in size than a Second Dwelling Unit, with a maximum size of 500 square feet.
  • A Junior Second Unit may have either independent bathroom facilities or shared facilities with the main residence.
  • A Junior Second Unit does not need to have a full kitchen, but must provide a limited food preparation area.
  • A Junior Second Unit must maintain an internal connection with the main residence, which can be equipped with a double lock.
  • A Junior Second Unit does not require additional parking. However, a Junior Second Unit only may be permitted where the primary residence meets the current residential parking standard of two (2) covered parking spaces.

What is the Review Process?

Junior Second units are subject to ministerial review by the Planning Division prior to issuance of a building permit. A Junior Second unit review fee ($300) and application form along with project plans (3 sets) must be submitted to the Planning Division, which will verify that the unit would comply with the prescribed Junior Second Unit Standards. If building permit clearance is granted, a Junior Second Unit deed restriction must be recorded for the property upon permit issuance and prior to occupancy.

Can an Existing (Unpermitted) Junior Second Unit be legalized?

Yes. The unit must meet all requirements for a Junior Second unit, and obtain planning review of a Junior Second Unit. Building permit fees to legalize an existing unauthorized Junior Second unit may be subject to additional research and inspection fees.

The following Standards apply to a Junior Second Unit:

  • Density/Size Limitation - A maximum of one Junior Second unit shall be permitted per residential lot containing a single-family dwelling, and is considered a permitted single-family residential use. A Junior Second unit shall not exceed 500 square feet in size. A single residential parcel can have either one (1) Second Dwelling Unit OR one (1) Junior Second Unit. Establishment of a single-family residence with either a Second Dwelling Unit or Junior Second Unit as part of the use is distinguished from a duplex use based on the definitions and performance standards that apply in either case.
  • Owner Occupancy and Deed Restriction - The property owner must occupy either the main single-family unit or the Junior Second Unit. A deed restriction must be recorded with the County Recorder so that future owners of the property will be aware of the requirements (such as owner occupancy). The sample format for the deed restriction is attached to this handout. Proof of recordation must be submitted to the Planning Division prior to issuance of a building permit or after Junior Second Unit application has been processed, and before the unit is completed and occupied.
  • Unit Access - A separate exterior entry shall be provided to serve the Junior Second unit. Interior access between the Junior Second unit and the main residence is required, and can be a door equipped with a double lock.
  • Utility Service - Water and sewer service for the Junior Second unit is shared with the main single-family dwelling unit, and shall not require a separate water or sewer meter connection. Currently, no additional sewer or water fees should be required for the Junior Second Unit (check with the Utility Service Provider).
  • Food Preparation Area - A Junior Second unit shall include a food preparation area, requiring and limited to the following components: a. A sink with a max. width and dimension of 16 inches and a max. waste line diameter of 1.5 inches b. A cooking facility or other appliance, including a refrigerator, which does not require electrical service greater than 120 volts or natural or propane gas c. A food preparation Counter and storage cabinets which do not exceed 6 feet in length.
  • Off-Street Parking - The main single-family dwelling must meet the current off-street parking standard in effect at the time the Junior Second unit is approved (i.e., two covered parking spaces). Otherwise, no additional off-street parking is required to be provided for the Junior Second Unit.
  • Building and Fire Code Requirements
    • No fire wall separation or noise attenuation measures are required between the main dwelling and the Junior Second unit.
    • No fire sprinklers shall be required for the Junior Second unit unless the associated improvements meet the threshold for a “substantial remodel” as defined by Chapter 4.08 (Fire Code) of the San Rafael Municipal Code.
    • A smoke alarm shall be required in the Junior Second unit and shall be connected to the smoke alarms in the main residence.
    • The Junior Second unit shall be equipped with a carbon monoxide detector.
    • Minimum room areas and dimensions may be required pursuant to the Building Code, as determined by the Building Official.

Junior Second Unit Handout


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