Abstract: At 6:50 a.m. on June 20, 2001, Employee #1, a welder, was seriously injured when he fell about 25 feet while standing on panelized roofing. The employer was erecting the roof structure on a tilt-up industrial building as a subcontractor. The outside joist was attached to the panel on the ground and placed on the girders using a Gradall excavator. When the joist ends did not seat properly on the girders for welding, the Gradall was placed against the outside girder to apply pressure so proper welding could be accomplished. Three panels had been placed on the girders and the Gradall had to be used to align the joist for welding. Another employee, the foreman, operating the Gradall, observed the welding of the joist on Panel 3 to the inside girder. After Panels 1 and 2 had been welded to the outside girder the Gradall pressure was released, since Employee #1 had walked back to Panel 1 and was talking to the welding inspector. Shortly thereafter both Employee #1 and the inspector fell as the panel upon which they were standing and Panel 2 fell, causing Panel 3 to also fall. Emergency Medical Services was called and paramedics arrived in about 10 minutes and transported the employee and inspector to a local trauma center. Employee #1 sustained a fractured left wrist and knee along with some dental damage. The inspector received a fractured pelvis and some fractured ribs. Employee #1 and the welding inspector were wearing fall protection harnesses hooked to preset clips on panels when working within 6 foot of the leading edge. The investigation revealed that Joist 1 and 2 were only welded to the outside girder and Joist 3 was only welded to the inside girder. The welding to the other joist and girder points was not completed.