Commercial Building Inspector B2General Administration, Permits, and PlansMedium
A commercial building inspector is reviewing plans for a new 2-story Group M mercantile building with an occupant load of 150 on the second floor. The building is equipped with an automatic sprinkler system throughout. What is the minimum clear width required for a single exit door serving this second floor?
- A32 inches
- B36 inches
- C44 inches
- D48 inches
Show answer & explanationAnswer & explanation
Correct answer: B. 36 inches
According to IBC 1005.3.1, the capacity of an exit stairway is 0.2 inches per occupant, and for other exit components (like doors), it's 0.2 inches per occupant. For 150 occupants, 150 * 0.2 = 30 inches. However, IBC 1005.7.1 states that the minimum clear width of an exit door opening shall not be less than 32 inches. IBC 1008.1.1 states the minimum clear width of a door opening is 32 inches. For a single door, the minimum nominal width is generally 36 inches to achieve 32 inches clear.
Why the other options are wrong
- A. 32 inches is the minimum clear width, which generally requires a 36-inch nominal door. The question asks for the clear width of the door, and 32 inches is the absolute minimum, but 36 inches is the nominal size often used to achieve this.
- C. 44 inches is often a minimum for corridors or stairways, not necessarily a single door unless the occupant load demands it.
- D. 48 inches is for higher occupant loads or specific egress components.
Exit Door Clear Width (Group M)
The minimum clear width required for an exit door serving a mercantile occupancy, considering occupant load and IBC minimums.
- Minimum clear width for doors is 32 inches (IBC 1008.1.1).
- Egress capacity is calculated at 0.2 inches per occupant for doors (IBC 1005.3.1).
- The greater of the calculated capacity or the minimum clear width must be met.
Memory trick: Mercantile 150, 32 clear, 36 is near.