Abstract: At approximately 3:15 p.m. on April 13, 1992, Employees #1 and #2, both carpenters, were standing on a section of roof when the joist supporting that section pulled loose from one of its hangers. The plywood roof section collapsed and they fell 21 ft onto a concrete floor. Employee #1 fractured his left elbow and shin, and Employee #2 fractured his left elbow and sustained head trauma. A supervisor saw the roof collapse and called 911 after checking on the injured employees, who remained conscious. Paramedics arrived in approximately 5 minutes and the employees were airlifted to a local hospital. Subsequent investigation revealed that the joists supporting the plywood sheathing did not contain the required web stiffeners and were not braced to prevent buckling or rollover.