Building Official Determination 21-05: Habitable vs. Non-habitable Accessory Structures

QUESTION: When is a heated detached accessory building considered a “non-habitable” structure and, therefore, exempt from permits under Section R105.2(1)?

RESPONSE: The Oregon Residential Specialty Code (ORSC) does not require a building permit for non-habitable detached one-story accessory structures with a building area 200 square feet or less. State of Oregon Statewide Code Interpretation 03-01 clarifies that the structure can be heated and still be considered "non-habitable" as long as it does not have a living room, dining room, kitchen, bedroom, or any combination of these types of rooms.

Since "living room" can apply to a variety of uses, the City of Portland will allow a heated accessory structure that meets the size and height limitations of R105.2(1) to be exempt from a structural building permit if it meets all the following conditions:

1. The structure does not contain a kitchen.
2. The structure will not be used for overnight sleeping.
3. The structure will not be used for a business, including licensed child care and home-based businesses operating under a Home Occupation Permit.

Where the accessory structure includes a covered porch, the floor area will be measured to the edge of the dripline of the porch cover.

Note: Although a structural building permit is not required, the work must still be constructed to the provisions of the building code. The exemption from a structural permit does not negate required trade permits when applicable such as electrical, mechanical, and plumbing. The accessory structure may require a zoning permit. Zoning requirements for floor area and building coverage limitations on the lot apply. Please check your zoning allowances by calling the Zoning Information Line at 503-823-7300 or scheduling a 15-Minute Question Appointment.

HISTORY: Implemented December 5, 2019. Revised May 17, 2021 and March 8, 2024.

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