Four-Story Infill: Single Stair, Change of Occupancy, and Accessible Entry
A 1925 four-story, 18,000 sf building is being converted: 4,500 sf retail on grade and 4,500 sf of business office on each of floors 2–4. The only interior stair is 44 in wide with 36-in clear doors at each floor; the building has no sprinkler and no exterior stair. The owner wants to keep the single stair and spend $180,000 on a new fire alarm and partial sprinkler instead of adding a second stair, which would consume 220 sf of leasable area per floor. The ground-floor retail entrance has a 30-in clear opening, a 4-in step, and no accessible toilet room. The architect has been asked to submit a code summary before the tenant improvement permit. The local jurisdiction has adopted the IBC and IEBC, and the building is not historic.
1. Calculate the occupant load and evaluate whether the existing 44-in stair can serve the proposed occupancy. What code path should the architect recommend?
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Retail: 4,500 sf ÷ 60 gross = 75 occupants. Business: 4,500 sf ÷ 150 gross = 30 per floor, or 90 for floors 2–4. Total = 165 occupants. At 0.3 in per occupant for an unsprinklered building, required stair width = 165 × 0.3 = 49.5 in; the existing 44-in stair is undersized even before considering the single-exit problem. A full sprinkler system would allow 0.2 in per occupant, or 33 in, so capacity would appear adequate, but capacity is not the only test. IBC 1006 requires two exits for this occupant load and building height. The IEBC change-of-occupancy provisions require the means of egress to comply with the new occupancy; a single stair is a fundamental deficiency, not a work-area item that can be deferred. The architect should recommend a second enclosed stair or an approved exterior stair and should not rely on sprinklers alone to cure the single-exit condition.
2. The owner argues that the $180,000 sprinkler and fire alarm package is a better use of money than losing 660 sf of leasable area. How should the architect respond?
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The architect should separate the life-safety benefits of sprinklers from the code requirement for a second exit. Sprinklers improve survivability and may reduce required egress capacity and some construction requirements, but they do not generally permit a four-story building with 165 occupants to have only one interior stair. The lost area is a real cost, but the code does not treat it as optional. The architect should present alternatives: an exterior stair may avoid interior area loss; a new stair can sometimes be placed in a light well or at an existing shaft; or the program can be reduced. If the owner wants to pursue a single-stair alternative, the architect should explain that it would require a formal code modification or variance with a demonstrated equivalent safety package, not a field decision. The architect should document the advice in writing and proceed only under an approved code path.
3. What accessibility improvements are triggered, and how should the architect sequence them against the owner’s budget?
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The 30-in clear entrance and 4-in step do not provide an accessible route. The change of occupancy and alteration trigger path-of-travel upgrades under the IEBC, with the 20% cost cap applying to the alteration cost, not to the whole project. The architect should first identify the primary function areas and the accessible route from the public way through the retail entrance to the toilet rooms and tenant spaces. The entrance is the highest priority because it is the gateway; the toilet room must be accessible if it serves the altered area. The architect should obtain a cost estimate for the entrance reconstruction and accessible toilet before deciding what else can be deferred. The 20% cap is a ceiling, not a design target, and the architect should document which elements are required versus discretionary. If the owner wants to phase work, the code summary should show the required scope for each permit phase.