Building Code Guides (BCGs) and Building Official Determinations (BODs) provide answers about the application of building codes and outline optional alternates. BODs are typically smaller in scope and address simpler questions. Code Guides provide a comprehensive alternative to a complicated set of code requirements.
BOD 21-03: Minimum Dwelling Unit Size
QUESTION: When do the requirements for efficiency dwelling units apply? Is there a minimum dwelling unit size in the City of Portland?
2019 Oregon Structural Specialty Code (OSSC) DEFINITION:
- DWELLING UNIT. A single unit providing complete, independent living facilities for one or more persons, including permanent provisions for living, sleeping, eating, cooking and sanitation.
2021 International Building Code (IBC) DEFINITION:
- DWELLING UNIT, EFFICIENCY. A dwelling unit where all permanent provisions for living, sleeping, eating and cooking are contained in a single room.
RESPONSE: The 2019 OSSC outlines the requirements for “efficiency dwelling units” in Section 1207.4 but does not indicate when these requirements must be applied. The 2021 IBC (not yet adopted) adds a definition for “efficiency dwelling unit” to clarify when to apply the requirements and decreases the minimum size from 220 sf to 190 sf. Therefore, the City of Portland will apply the clarified and more lenient requirements of the 2021 IBC.
Any dwelling unit that has living, sleeping, cooking, and eating provisions in one room is, by definition, an “efficiency dwelling unit” and the main room (where these activities are located) must be at least 190 sf.
A dwelling unit with more than one habitable room would follow the minimum room size requirements in 1207.3 which states that every dwelling unit must have at least one habitable room (the living/cooking area for example) with a minimum area of 120 sf, and other habitable rooms (a sleeping room for example) may be as small as 70 sf.
One- and two-family dwellings, including townhouses are governed by the Oregon Residential Specialty Code (ORSC) and are not subject to this Building Official Determination for structures under the scope of the OSSC.
Here are a few notes of clarification for application of this code section in the City of Portland.
1208.4 Efficiency dwelling units: Efficiency dwelling units shall conform to the requirements of the code except as modified herein.
- The unit shall have a living room of not less than 190 square feet of floor area.
CoP note: "Floor area" is intended to provide occupiable space and excludes built-in counters and kitchen appliances. In addition, required clear space for bike parking may not be included in the 190 square foot floor area.
- The unit shall be provided with a separate closet.
CoP note: The closet must be at least 3' wide and 2' deep.
- For other than Accessible, Type A and Type B dwelling units, the unit shall be provided with a kitchen sink, cooking appliance and refrigerator, each having a clear working space of not less than 30 inches in front. Light and ventilation conforming to this code shall be provided.
CoP note: The accessibility clearances for working spaces in the kitchen supersede the minimum dimensions listed here for efficiency dwelling units. See OSSC Section 1107 to determine if Accessible, Type A or Type B dwelling units are required.
- The unit shall be provided with a separate bathroom containing a water closet, lavatory and bathtub or shower.
HISTORY: Implemented June 4, 2021.
DOWNLOAD a copy of this Building Official Determination:
QUESTIONS? Free 15-Minute Appointments for Permit, Code, and Zoning Questions