Understanding "Occupancy Classification" in Plain Language

Occupancy classification sorts buildings and building areas into groups based on how they're used and, critically, the level of risk and the kind of occupants involved — a group home, a school, an office, a warehouse, and a single-family house are all classified differently, even if two of them happen to be similar sizes.

Almost every other major requirement in the code — required exits, fire separations, sprinkler requirements, allowable building height and area — flows from this classification. A building with a high occupant load or with occupants who may need help evacuating, like a care facility, gets stricter requirements than a low-occupancy warehouse of the same square footage, which is why classification is one of the first questions a code review actually asks.