Sprinklered Addition Triggers Egress Recheck at Mixed-Use Building
A three-story, 28,000 sq ft mixed-use building has retail on the first floor and offices above. The existing building is fully sprinklered per NFPA 13 and was permitted under an older code edition. The owner now adds a 4,000 sq ft second-floor office suite, increasing the second-floor occupant load from 55 to 110 and the building total from 210 to 265. The architect submits the addition as a Level 2 alteration and asserts that because the building is sprinklered, no egress changes are needed. The existing single interior exit stairway is 44 in. clear width with a 3 ft door at each landing. The corridor serving the new suite is 5 ft wide with a 7 ft 6 in. ceiling and a 12 in. deep soffit projecting into it along one side for 20 ft. The building official flags the submittal for egress review before issuing the permit.
1. Is the single exit stairway acceptable for the enlarged occupant load, and what analysis should the designer perform before resubmitting?
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Sprinkler protection does not by itself excuse exit capacity. The designer must first establish the occupant load of each floor and the egress capacity of the components serving it, then confirm the number of exits permitted for that load. With 110 occupants on the second floor, a single exit is generally allowed only where the code's occupant-load threshold for a single exit is not exceeded and the travel distance, common path, and stair enclosure requirements are all satisfied; at 110 the designer is close to or above the typical single-exit limit for business occupancy, so a second means of egress likely must be evaluated.
Capacity is checked separately. The 44 in. stair width provides roughly 44/0.3 = 146 persons of capacity (using the stair capacity factor of 0.3 in. per occupant), which is adequate for 110. The 3 ft door provides about 3 ft x 60 = 180 persons of capacity at 0.2 in. per occupant, also adequate. The controlling issue is therefore the number of exits and the egress path geometry, not raw width. The designer should document the occupant load, exit count, capacity, travel distance, and common path in a code analysis and resubmit; if a second exit is required, the plan must show it.
2. Evaluate the 5 ft corridor with the projecting soffit. What code issues arise?
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Two separate requirements apply. First, the minimum corridor width for the occupant load served must be verified. A 5 ft corridor is acceptable only if the required egress capacity does not demand more width; at 0.2 in. per occupant, 5 ft (60 in.) supports 300 occupants, so width alone is not the problem for a 110-person floor. Second, the 12 in. soffit projecting 20 ft along one side reduces the clear width at that location. The clear width must be measured to the projection, leaving 48 in., and the corridor must still meet the minimum clear width required for the occupancy and for accessibility. A 48 in. clear path is generally the minimum accessible route width, so the soffit leaves no margin and may violate the required corridor width if any additional encroachment exists.
The 7 ft 6 in. ceiling is also a concern: corridor ceilings are typically required to be at least 7 ft 6 in., and the soffit may reduce headroom below that where it projects. The designer should either remove or reduce the soffit, relocate it, or widen the corridor so the clear width and headroom remain compliant, and should show the dimensions on the plan. The submittal should include a dimensioned corridor section demonstrating compliance.