Egress Capacity in a Mixed-Use Tenant Fit-Out
A 1988 office tower floor is being fit out for a 9,600-sf tenant: open workstations for 96 people, a 24-seat conference room, and a 900-sf lunch and catering room with a warming kitchen. The floor is fully sprinklered. Two exits serve it - a 34-inch clear door into the north stair and a 36-inch clear door into the south stair, 118 ft apart on a floor whose diagonal between exits is 210 ft. The exit-access corridor is 44 inches clear, but the client wants an 8-inch-deep recessed art niche along a 12-ft section and a vendor wants a 3-inch-deep sanitizer cabinet at 40 inches AFF on the same wall. Travel distance from the farthest workstation is 195 ft.
1. What design occupant load should you use for this floor, and do the two existing exit doors have adequate egress capacity? Show the arithmetic.
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Occupant load
- Open workstations: 96 (given as a head count; do not re-derive at 150 gross sf if the furniture plan is fixed)
- Conference: 24 (net, at the table)
- Lunch/catering room: 900 sf ÷ 15 net sf per occupant (tables and chairs, unconcentrated) = 60
- Total = 180
The lunch room is the trap. If you carry it as a business break room you would get 900 ÷ 150 = 6, total 126. The 60-person figure matters because it pushes the room past the 50-occupant threshold that lets a room in a business occupancy be excluded from A-2.
Egress width (sprinklered building)
- Doors and corridors: 0.15 in per occupant × 180 = 27 in total
- Stairs: 0.20 in per occupant × 180 = 36 in total
Available door clear width is 34 + 36 = 70 in, well over 27 in. Each door provides at least half the required capacity, and each is at least the 32-in minimum clear width - both pass.
Do not stop at the doors. The doors tell you nothing about the stair width. Stairs serving 50 or more occupants have a minimum width independent of the calculation, so verify the actual stair throat on a site visit before you sign the fit-out drawings.
Other checks
- Travel distance 195 ft against the 250-ft allowance for a sprinklered B/A-2 floor - 55 ft of margin, acceptable, but confirm no egress path runs through the catering room if any cooking equipment is installed.
- Exit separation: 1/3 × 210 = 70 ft required; 118 ft actual. Passes comfortably.
2. The client wants the recessed art niche and the vendor wants the surface-mounted cabinet. Evaluate both against the corridor requirements and propose a resolution.
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Governing width
The corridor serves an occupant load over 50, so its minimum clear width is 44 in regardless of the 27-in calculated capacity. The required width may not be obstructed; handrails are the narrow exception, and even they cannot bring the clear width below the required minimum.
The niche
8 in deep reduces the corridor to 36 in at that run. That is below the 44-in minimum, so it cannot be approved as drawn.
The cabinet
3 in at 40 in AFF leaves 41 in clear. Still below 44 in. "Small" is not the test - the test is whether the required width survives.
Options to put to the client
- Locally widen the corridor to 52 in at the niche and 47 in at the cabinet (the depth plus the required width), furring out the opposite wall. Cleanest architecturally, costs floor area.
- Flush-recess the cabinet behind a door or a removable panel so it creates no projection.
- Move the display to the reception wall or the elevator lobby and leave the corridor clean.
- Replace the niche with a surface-mounted, frameless display not exceeding the permitted projection limit - only if the remaining clear width still meets 44 in, which it does not here.
Don't miss
A deep recess creates a concealed space above and beside it. Check sprinkler coverage into the recess and the combustibility of the display materials; an unprotected alcove is a common plan-review comment. Also confirm the cabinet is outside the door-swing and maneuvering clearances at the stair doors.
3. The contractor argues the lunch room is 'just a break room' and should be counted as business occupancy at six occupants. How do you resolve the classification, and what changes downstream if it is A-2?
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Resolution
- A room within a business occupancy is excluded from A-2 only while its occupant load stays under 50. At 60 it does not qualify for the exclusion, so it must be evaluated as assembly.
- It can still be an accessory occupancy without a fire separation if it is ancillary to the business use and its area is within the accessory limit - 900 ÷ 9,600 = 9.4%, under the 10% ceiling, and within the tabular area and height limits for A-2 in a sprinklered building. Confirm the local adoption and the exact percentage with the AHJ.
- Document the call in a short occupancy-classification memo and get the AHJ to concur before permit. Do not let it be settled by a note on a drawing.
Downstream consequences if A-2 governs
- Egress is computed at 15 net sf per occupant, not 150 gross - the 54-person swing is what drives the two-exit analysis.
- Panic hardware is required on egress doors serving an assembly space at or above 50 occupants. The lunch room door hardware changes.
- The warming kitchen: if the equipment is microwave and convection only, no commercial hood. Add a range, fryer, or any gas-fired cooking and you are into commercial cooking ventilation and a different occupancy/equipment review.
- Fire alarm and notification coverage may need review for an assembly use on the floor.
The judgment the exam is testing is that 'it's just a break room' is a description, not a classification - and that the classification is made on occupant load and area, not on the client's intent.