Which approach should be used to determine occupant load for a building with two distinct occupancies on the same floor?

Which approach should be used to determine occupant load for a building with two distinct occupancies on the same floor?

• A. Use the larger occupancy's load only.
• B. Use the occupancy with the higher hazard only.
• C. Calculate each occupancy separately and add them together.
• D. Take the average of the two occupancies.

Answer: (C)

Two occupancies on one floor require treating each space’s occupant load separately and then combining them. Each occupancy has its own occupant load factor, which reflects how many people are expected per unit area for that use. To determine the total load, multiply the area of the first occupancy by its factor, multiply the area of the second occupancy by its factor, and then add the two results. This sum represents the maximum number of occupants that could be on that floor if both occupancies are in use, which is the figure used to size exits, stair enclosures, and other life-safety provisions. Relying on just the larger load, the higher hazard load, or an average would not capture the potential combined occupancy, potentially underestimating the required egress capacity. The correct approach—calculating each occupancy separately and adding them—ensures the design accounts for the worst-case together.

Two occupancies on one floor require treating each space’s occupant load separately and then combining them. Each occupancy has its own occupant load factor, which reflects how many people are expected per unit area for that use. To determine the total load, multiply the area of the first occupancy by its factor, multiply the area of the second occupancy by its factor, and then add the two results. This sum represents the maximum number of occupants that could be on that floor if both occupancies are in use, which is the figure used to size exits, stair enclosures, and other life-safety provisions.

Relying on just the larger load, the higher hazard load, or an average would not capture the potential combined occupancy, potentially underestimating the required egress capacity. The correct approach—calculating each occupancy separately and adding them—ensures the design accounts for the worst-case together.