Second-Floor Studio in an Unsprinklered Office Building: Occupant Load and Exit Count
A 1998 two-story office building of 7,500 sq ft per floor has never been sprinklered. The second floor holds open office use and is reached by one enclosed interior stair at the north end that discharges into the first-floor lobby; a second exterior stair was removed in a 2009 remodel under permit. A tenant now wants to convert 2,200 sq ft of the second floor into a martial arts studio for children and adults, with the remaining 5,300 sq ft staying business use. The architect's plan sheet lists 44 occupants for the studio and 35 for the office, for a total of 79, and concludes that one exit is adequate because "the floor is existing and the total is under 100 occupants." The longest travel path from the far corner of the studio to the stair door measures 140 ft. The shared corridor is 44 in wide, the stair is 44 in wide, and the stair door is 36 in wide.
1. Recompute the occupant load and determine whether a single exit from the second story is permitted.
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Recompute space by space and round each result up, because the tabular load factors differ.
Studio, assembly use without fixed seats, gross floor area method at 50 sq ft per occupant: 2,200 / 50 = 44. Office at 150 sq ft per occupant: 5,300 / 150 = 35.33, which rounds up to 36, not down to 35. Total design occupant load for the story is 80, not 79.
That one-person difference matters, but the architect's error is larger. The one-exit allowance for an unsprinklered business story is capped far below 80 occupants and carries a travel-distance limit in the range of 75 ft; both are tabulated in the exit-access chapter and must be checked in the edition in force. Here the story exceeds the occupant cap and the 140 ft travel path roughly doubles the limit, so a second exit is required.
Also flag the assembly space as a separate occupancy: at 2,200 sq ft it is well over ten percent of the floor area, so it cannot be treated as incidental and the required separation from the business occupancy must be shown.
2. Evaluate the corridor, stair, and door widths, and state which doors must swing in the direction of egress.
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Capacity first, then minimums, then the governing constraint.
Required egress capacity at 0.2 in per occupant for 80 occupants is 16 in, which is trivial. The table minimums govern: a 44 in corridor and 44 in stair exceed the minimums for this occupant load, so width is not the defect. Note, though, that the stair must be sized for the total load of every story it serves, not just the second floor. Add the first-floor office load of roughly 50 occupants and the stair is carrying about 130 people, requiring roughly 26 in of capacity; the 44 in stair still works, and the calculation should be shown.
The 36 in stair door yields roughly 33 in of clear width, above the 32 in minimum.
Door swing: doors serving a space with an occupant load of 50 or more must swing in the direction of egress. The stair door serves the whole story at 80 occupants, so it must swing in the direction of egress and be provided with the panic hardware or latching the occupancy requires. The studio door serves 44 and is not individually triggered, but it opens onto the shared path of travel, so its swing must not obstruct capacity.
3. The owner says a second stair is physically impossible. What compliant paths exist, and how do you document your position?
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Four realistic paths, in rough order of practicality.
One, sprinkler the building throughout with a code-compliant system. This substantially enlarges the one-exit allowance and travel-distance limits for the story and commonly eliminates the assembly-to-business separation. It does not make one exit unlimited; recheck the sprinklered caps against the 80 occupant load before promising anything.
Two, reduce the scope so the story drops under the one-exit cap. With 36 office occupants already there, the studio would have to shrink to about 13 people, which is likely unworkable but is the honest arithmetic.
Three, provide the second exit by another means: an exterior stair, a new enclosed stair, or a horizontal exit into a properly rated area of the building.
Four, submit a code modification or alternate-methods request to the building official, with engineering justification, and note the board of appeals route.
Document the calculation, the two governing limits, and the date you communicated them. Do not issue any certificate of occupancy until the exit question is resolved, and put the sprinkler option in writing so the owner cannot later claim it was never offered.