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Under what conditions may a four-story residential structure be regulated under the ORSC? We answer your questions about the application of building codes and outline optional alternates.
Building Code Guides (BCGs) provide a comprehensive alternative to a complicated set of code requirements.
BCG 12-11: Four-Story Code Guide
QUESTION: The scope of the Oregon Residential Specialty Code (ORSC) is limited to structures not more than three stories above grade plane. Under what conditions may a four-story residential structure be regulated under the ORSC?
RESPONSE: Four story residential structures, including those with enclosed useable and/or habitable space on all four stories, may be regulated under the ORSC provided all of the following conditions are met:
- NFPA 13D fire sprinklers shall be installed throughout the structure, under a permit from Portland Permitting & Development.
- Where an ADU is present within a four-story structure, an NFPA 13-R sprinkler system shall be installed throughout the structure under a separate permit from the Fire Marshall’s Office;
- Four story structures with more than 2,000 square feet of total enclosed space and enclosed useable and/or habitable space on more than three stories, shall have at least two egress doors to the exterior. Each required egress door shall be located on a different story, and shall be located at grade, or be provided with access to grade via a code compliant ramp or stairway.
- Where an ADU is present within a four-story structure, two egress doors shall be provided from each dwelling unit having enclosed usable space on more than three stories. Each required egress door shall be located on a different story, and shall be located at grade, or be provided with access to grade via a code compliant ramp or stairway;
- Structures with enclosed useable and/or habitable space on four stories shall not also have a basement, a mezzanine, or a roof deck (five levels);
- The underside of the lowest floor shall be protected with 5/8-inch gypsum sheathing or shall be protected with additional fire sprinklers;
- Exposed vertical posts supporting the lowest floor shall have a minimum solid sawn size of 6-inches by 6-inches, or be of noncombustible construction, and;
- The structural design for the entire structure shall be prepared by a licensed design professional registered in the state of Oregon.
HISTORY: Implemented May 1, 2012. Revised August 17, 2022.
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