Building Code Guide 25-10: Single Stair Apartments

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BCG 25-10: Single Stair Apartments  

QUESTION: The Oregon Structural Specialty Code (OSSC) limits apartment buildings with one exit stair to three stories. Are there alternative design options that would allow a taller building to be served by a single exit stair?

RESPONSE: The City of Portland will allow use of the 2025 OSSC Appendix Q provisions listed below, with one additional condition required by Portland Fire & Rescue as the local fire service referenced in Q101.1.

Note: Italicized terms are defined in OSSC Chapter 2.

In addition to the means of egress requirements of Chapter 10, buildings containing Group R-2 dwelling units shall be permitted to be served by a single exit stairway under the following conditions:

1. The building shall not exceed four stories above grade plane in building height. The application of Section 510 is not permitted.
2. The net floor area of each story shall not exceed 4,000 square feet.
3. Not more than four dwelling units shall be located on any story.
4. Exit access travel distance shall not exceed 125 feet.
5. Openings to interior exit stairway enclosures shall be limited to those required for exit access into the enclosure from normally occupied spaces, those required for egress from the enclosure, and openings to the exterior. Elevators shall not open into the interior exit stairway enclosure.
6. Emergency escape and rescue openings shall be provided in accordance with Section 1031.
7. A manual fire alarm system and automatic smoke detection system that activates the occupant notification system in accordance with Section 907.5 shall be provided. Smoke detectors shall be located in common spaces outside of dwelling units, including but not limited to; gathering areas, laundry rooms, mechanical equipment rooms, storage rooms, interior corridors, interior exit stairways, and exit passageways.
8. Regardless of the building or stairway type of construction, automatic sprinkler locations in interior exit stairways shall comply with the requirements of NFPA 13 for combustible stairways.
9. Electrical receptacles shall not be permitted in interior exit stairways.
10. Mezzanines and sleeping lofts are not permitted.
11. A minimum of one dominant street-facing building façade shall meet Portland Fire Code requirements for fire apparatus aerial access, including a minimum unobstructed width of 26 feet exclusive of shoulders or parking. Overhead utility and power lines shall not be located within the aerial fire apparatus access roadway or be located within 10 feet of an aerial ladder extended from the fire apparatus access road to the roof of the building.

HISTORY: Implemented October 22, 2025.

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