Standpipes give firefighters a water supply inside the building, and IBC 905 sets where they're required and which class. Class I serves fire-department use (2½-inch hose connections), Class II serves occupant use (1½-inch), and Class III provides both. Standpipes are generally required where the highest or lowest occupied floor is more than a set distance (commonly 30 feet) above or below fire-department vehicle access, in large-footprint assembly occupancies, covered malls, stages, and similar conditions.
The common mistake is missing the height trigger — a building whose top floor sits just over the threshold above grade access — or providing the wrong class for the occupancy. Reviewers check the floor heights relative to fire-access grade and the occupancy/area triggers in 905, and confirm the standpipe class and hose-connection locations. Because standpipes tie into the sprinkler riser and stair design, catching the requirement early avoids reworking the risers and stair enclosures later.
This guide describes the model code for general understanding and is not a substitute for the adopted code and amendments enforced by your local authority having jurisdiction. Verify all figures against your jurisdiction's codes of record.