Accessory Dwelling Units

Accessory Dwelling Unit (ADU)

Accessory Dwelling Units have been known by many names including, granny flats, in-law units, backyard cottages, secondary units, and more.  Basically, an ADU is a second, smaller home unit with complete independent living facilities including a living area; a sleeping area; a full kitchen with a stove, refrigerator, and sink; and bathroom facilities with a sink, toilet, and bath/shower. ADUs may be detached from, attached to, or contained entirely within the main house.

Accessory Efficiency Dwelling Unit (AEDU)

An Accessory Efficiency Dwelling Unit is a second, smaller home unit with independent living facilities including, a combined living/sleeping area; a bathroom with a toilet, sink, and bath/shower; and a full or partial kitchen that has at least a sink and refrigerator. An AEDU may be detached from, attached to, or contained within the main house. An AEDU, as defined herein, shall be considered an ADU.

Junior Accessory Dwelling Unit (JADU)

A Junior Accessory Dwelling Unit is a second, smaller home unit with independent living facilities including a combined living/sleeping space with an efficiency kitchen that includes a cooking area with appliances, sink, counter, and cabinets. A JADU can be contained entirely within the main house or its attached garage. Also, it may include a separate bathroom, or it may share a bathroom with the main house.


Eligible Sites - Properties within a single-family residential zoning district with an existing or proposed single-family home, unless located in the ADU Ineligibility District (CHMC 16.10.140(H). For ADUs within multifamily or mixed-use zoning districts, please see CHMC 16.10.140(I)(2). 

Number of ADUs - Maximum of one (1) ADU or JADU per property.

Maximum Lot Coverage - ADUs larger than 800 square feet are subject to the maximum lot coverage of the zoning district, unless the ADU is entirely within the main house or its garage.

Minimum Size - 220 square feet

Maximum Size 

  • Detached ADU: 850 square feet for 1 bedroom or 1000 square feet for 2+ bedrooms
  • Attached ADU: Same as detached, except that the total floor area of the ADU cannot exceed 50% of the main house floor area (for units over 800 square feet). There is no maximum size for ADUs converted within existing house.
  • JADU: 500 square feet

Maximum Height 

  • 16 feet for a one-story 
  • A two-story ADU may be permitted where the ADU is located behind the main house and complies with the setbacks applicable to the main house. The height shall not exceed the maximum height of the zoning district.

Minimum Setbacks 

  • Front yard: same as the main house
  • Side yard: 4 feet (interior & side street)
  • Rear yard: 4 feet
  • ADUs and JADUs constructed within the main house shall have the same setbacks as the main house.

NOTE: The 4-foot setback to the side and rear property lines shall begin at the eave/overhang of the roof.

Minimum Building Separation - 10 feet except when located within the Fire Hazard Overlay which has a minimum building separation of 30 feet. Building separation is not required if the ADU is built of 100% non-combustible materials.

Entry/Access - Exterior access for ADUs and JADUs must be independent from the main house.


  • Detached ADU: fully independent water, sewer, gas & electric lines with separate connections and meters
  • Attached ADU: may share utilities with the main house
  • JADU: may share utilities with the main house

Kitchen Requirements

  • Detached ADU: full kitchen (stove, refrigerator, and sink)
  • Attached ADU: full or partial kitchen (sink and refrigerator) requied
  • JADU: efficiency kitchen (stove, sink, countertop, cabinets)

Bathroom Requirements 

  • Detached ADU: full bathroom (including shower and/or tub)
  • Attached ADU: full bathroom (including shower and/or tub)
  • JADU: may share with main house or have its own bathroom

Parking Requirements - One space (not on the street) for any ADU with one or more bedrooms, in addition the required parking for the main house, unless exempt. See exemptions below.

  1. house is located within 1/2 mile of public transit; OR
  2. ADU is entirely within an existing home or its garage; OR
  3. where on-street parking permits are required but not available; OR
  4. located within one block of a car share vehicle

Occupancy Requirements 

  • Detached ADU: none
  • Attached ADU: none
  • JADU: the property owner must live in the main house or the JADU

Deed Restriction - A restrictive covenant shall be recorded stating that the ADU/JADU will not be sold separately from the main house and that any rental or lease of the ADU/JADU will be for greater that 30 days.

Rental Period - Any rental or lease of an ADU must be at least 31 days.

Development Impact Fees - DIFs are required for ADUs 750 square feet or larger and do not apply to JADUs.

For further, more detailed information, please view the ADU handout.