Want to build a small structure on your Portland property? You’re definitely not alone. Depending on the structure size, construction type and use, it could be classified in various ways. This table covers the basics for:
- Accessory dwelling units (detached fully functional small homes)
- Detached bedrooms (habitable accessory structures)
- Garages, artist/yoga studios… (permitted accessory structures); and
- Storage sheds, chicken coops, kid’s forts, greenhouses… (unpermitted accessory structures)
If you’re interested in homes-on-wheels, look for a future post on applicable Portland regulations soon.
Disclaimer: This guide is not authoritative, is overly simplified in places, and should not be relied on for accuracy. To get the full scoop, read up on the zoning and building codes directly and/or consult with Bureau of Development Services staff on the 1st floor of the 1900 SW 4th Ave. building in downtown Portland.
 Per Chapter 29.10 Definitions, “Habitable room or space is a structure for living, sleeping, eating or cooking. Bathrooms, toilet compartments, closets, halls, storage or utility space, and similar areas are not considered habitable space.”
 If plans for a habitable, detached accessory structure suggest the potential for that the structure to be used as an independent dwelling, the city may require the applicant to sign and record a ‘Second Sink Agreement’ against the property.
 For gable roofs, height is measured to the mid-point of the gable
 Maximum household size, per ‘definitions’ section of the zoning code: “One or more persons related by blood, marriage, legal adoption or guardianship, plus not more than 5 additional persons, who live together in one dwelling unit; or one or more handicapped persons as defined in the Fair Housing Amendments Act of 1988, plus not more than 5 additional persons, who live together in one dwelling unit.”
- Certain zoning code requirements, including setbacks, lot coverage, size limits, and design standards, can sometimes be modified through a zoning adjustment process. See section 33.805 of the zoning code or contact BDS staff for additional information.
- There is wide latitude in building methods and materials for foundations, walls, roofs… in unpermitted structures. However, if a structure is not permitted initially, subsequent conversion to a different use for which a permit is required (such as a habitable structure) could be difficult or impossible, depending on the original building methods and materials used.
- Portland’s Zoning Code
- Code guide for conversions of garages or attics to habitable use
- “Do I Need a Permit for my Project?” brochure