Richmond refers to ADUs as “Second Dwelling Units.”
Details are given in Section 15.04.810 of their Municipal Code.
A second dwelling unit is an attached or detached residential dwelling unit which provides complete independent living facilities for one or more persons. It shall include permanent provisions for living, sleeping, eating, cooking and sanitation on the same parcel as a legally created dwelling unit. A second dwelling unit may be created by:
A. Alteration of an existing residential structure whereby separate cooking, eating, sleeping and sanitation facilities are created, and includes a separate entrance/ exit door from the main residential structure;
B. Conversion of an attic, basement, or other previously uninhabited portion of a residential structure, as specified in this section, that includes a separate entrance/exit door from the main residential structure;
C. Creation of a separate residential unit onto an existing residential structure;
D. Creation of a detached residential unit, no larger than 640 square feet, within the building envelope or in the rear yard of the lot and subordinate to the main residential structure;
E. Manufactured housing may be permitted.
A second dwelling unit permit will only be issued if it complies with the following development standards:
A. Setbacks. 2011 1. Residential Districts. For attached second dwelling units, all requirements and regulations of the zoning district in which the lot is situated shall apply, including but not limited to height, lot and yard requirements, and lot coverage. Detached second dwelling units are subject to the height, setbacks and yard area requirements set forth in this section. No detached second dwelling unit shall be closer than 10 feet to the main dwelling on the same lot and on adjacent lots. A second dwelling unit shall not be closer than 5 feet from any property line or accessory structure on the same lot. 168 15.04.810 2. PA (Planned Area) Districts. A second dwelling unit shall not be in conflict with any applicable planned area district regulations.
B. Unit Size. 1. No newly constructed second dwelling unit may have more than two bedrooms, nor contain a floor area in excess of 640 square feet. Efficiency units shall not contain less than 150 square feet. 2. Internal Conversion. The floor area of an attached second unit shall not exceed 30°;() of the existing living area of the main dwelling unit or 640 square feet, whichever is less.
C. Height. A detached second dwelling unit shall not exceed two stories. The maximum building height for a second dwelling unit is 22 feet.
D. Off-Street Parking. One uncovered paved off-street parking space shall be provided for the second dwelling unit in addition to the covered parking space(s) required for the existing residence. Tandem parking shall not be allowed. The required parking space for the second dwelling unit may be provided in the required front yard if pad and driveway are paved with a decorative treatment such as aggregate, brick, pavers, or similar materials.
E. Architectural Compatibility. The second dwelling unit shall be clearly subordinate to the main dwelling unit on the lot with regard to size, location and appearance. The exterior design shall be compatible with the main dwelling unit and shall incorporate same or similar building materials, colors, and exterior surfaces and finishes as those on the main dwelling unit.
F. Privacy. Any window or door of a 2nd story second dwelling unit shall utilize techniques to lessen the privacy impacts onto adjacent properties. These techniques may include use of obscured glazing, window placement above eye level, orienting windows and doors toward the existing on-site residence, and/or screening treatments.
G. Permanent Foundation. A permanent foundation shall be required for all second dwelling units.
H. Outside Access. Outside access to a second dwelling unit shall be separate from the main dwelling unit.