Plan Review Conflict Between a Sprinklered Corridor and Required Exit Access
A plan review submission for a new 5-story, 60,000 sq ft Group R-2 apartment building shows a single interior exit stairway serving all floors. The building is fully sprinklered and has a 13R automatic sprinkler system. The corridor system is 4 feet wide and serves 22 dwelling units per floor. The applicant cites the sprinkler system and the presence of a corridor as justification for a single exit. The plans examiner notes that the stairway is enclosed in a 1-hour shaft and that each dwelling unit has a sprinkler head at the entrance. The examiner must determine whether a single exit is permitted and whether the corridor width is adequate.
1. Is a single exit permitted for this building, and what factors govern the answer?
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The examiner should analyze the exit configuration against the code's provisions for number of exits.
Occupant load and number of exits. The number of required exits depends on the occupant load served and the occupancy. For Group R-2, the code generally requires at least two exits from each floor when the occupant load exceeds a threshold, and the threshold is lower for buildings of this height. A 5-story building with 22 dwelling units per floor has a substantial occupant load, and a single exit is typically not permitted regardless of sprinklering.
Sprinkler system type. The applicant cites a 13R system. A 13R system is a residential sprinkler system designed for life safety, not a full 13 system. Some code allowances for single exits or increased travel distance require a full 13 system, not 13R. The examiner should verify which system is actually installed and whether the code provision relied upon permits 13R.
Corridor and exit access. Even where a single exit is permitted under narrow conditions, the code imposes limits on travel distance, common path, and the number of dwelling units served. The examiner should confirm that those limits are met.
Conclusion. Based on the height and unit count, a single exit is unlikely to be permitted. The examiner should require a second exit or a code modification supported by a design professional and approved by the building official, and should not accept the presence of a corridor and a 13R system as sufficient justification.
2. Evaluate the 4-foot corridor width against the code requirements.
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Corridor width must be evaluated against both the minimum clear width and the required egress capacity.
- Minimum clear width. The code generally requires corridors serving an occupant load of 50 or more to have a clear width of at least 44 inches, and corridors serving fewer occupants may be permitted at 36 inches. For a residential corridor serving 22 dwelling units, the occupant load likely exceeds 50, so a 4-foot (48-inch) corridor may satisfy the minimum width, provided obstructions such as columns, hose cabinets, or projecting doors do not reduce the clear width below the minimum.
- Egress capacity. The corridor width must also provide sufficient capacity for the occupant load it serves. The examiner should calculate the occupant load for the floor, apply the capacity factor for corridors, and confirm the required width. A 48-inch corridor may be adequate for 22 units, but the calculation should be documented.
- Door swing and projections. The examiner should verify that dwelling unit doors do not swing into the corridor in a way that reduces the required width, and that any projections comply with the permitted encroachment limits.
- Conclusion. The 4-foot corridor may be acceptable if the clear width is maintained and capacity is adequate, but the examiner should require the applicant to demonstrate the occupant-load calculation and verify that no obstructions reduce the clear width below the minimum. The corridor width does not cure the single-exit deficiency.