Unusable space in occupant load calculations includes which item?

• A. Columns
• B. Windows
• C. Doors
• D. Flooring

Answer: (A)

In occupant load calculations you start with the net usable floor area—what people can actually occupy. Structural elements that take up space but can’t be occupied, like columns, are considered unusable because they reduce the space available for people. That’s why columns are subtracted from the gross area when figuring how many occupants a space can safely hold. Windows and doors don’t occupy usable floor space in the same way, since they’re openings in walls, and flooring is the actual usable surface, so they’re not treated as unusable. Flooring is part of the space people stand on, not something that excludes occupancy.