Appeal 33612

OSSC 403.5.1

This is a re-appeal: 33557, 33581

OSSC 403.5.1 specifies that in high-rise buildings, interior exit stairways must be located remotely from each other to ensure redundancy. This code section expressly identifies that scissor stairs shall be counted only as one interior exit stairway.

This code re-appeal seeks authorization to use a single scissor stair configuration to satisfy the exit requirements of IBC 1006.3 and OSSC 403.5.1 in a high-rise building, providing two egress paths within a limited footprint while ensuring compliance with safety and functional standards.

We are developing an affordable housing project in Portland that maximizes density by leveraging the city’s new Floor Area Ratio (FAR) allowances, designed to encourage high-density, affordable construction. Our building, with a footprint of approximately 50x80 feet, achieves this increased density with a carefully designed scissor stair—the only viable solution to provide both required egress paths within the compact space.

We are providing equivalent fire, life, and safety protections in this scissor stair configuration by massively increasing the fire rating of every component of the stair shaft.

First, as shown in the updated plans, the stair shaft enclosure will have a minimum 4-hour rating arising from a 10" concrete wall. Thus, if there is a fire in the portion of the building outside of the stair shaft, the stair shaft will have a 100% increased fire rating and remain safer for longer. The exit doors will also be 3-hour rated.

Within the stair shaft itself, the two interlocking stairs will be separated by a 3-hour rated 6" concrete wall, while each of the landings will also be a 3-hour concrete landing. The stairs themselves will be pre-cast 3-hour-rated concrete. Will maintain this rating by filling all gaps with fire caulking.

And finally, we propose the addition of new sprinkler heads on each landing.

In sum, these two interlocking stairways will be completely separated from one another by three-hour materials. Additional sprinkler heads will operate to further extend fire protections in the unlikely event a fire begins in one of the stairwells. And finally, the entire stair shaft will be enclosed in a 4-hour wall, greatly reducing the likelihood that a fire from outside the stair shaft would breach the shaft.