Abstract: On August 27, 2007, Employees #1 through #3 were at an existing home site, where an addition was under construction. Seventeen 33 ft long by 8 ft tall webbed roof trusses were stacked on the 7-in-12 sloped roof of the existing house. The eave to ground height was approximately 25 ft. The sheathing for the second-story floor was in place on top of the first story, but the second-story exterior walls and load-bearing walls had not yet been constructed. The roof trusses for the addition had been hand-carried from the ground to the first story, and then up to the existing roof of the house, which was about 10 ft above the sheathing deck on top of the addition. The trusses, each weighing approximately 250 lb, were placed on the existing roof to make it easier to slide them and erect them onto the second story after the load-bearing walls were built. At approximately 9:00 a.m., four of the trusses slid about 9 ft down the existing roof, striking Employees #1 through #3 where they were working on the first floor. Employee #1 sustained a fractured right arm, contusions to his right shoulder, elbow, and wrist, and a sprained right knee and lower back. He was transported to a local hospital, where he was treated and released the same day. Employee #2 suffered minor injuries and was treated at the scene. Employee #3 was hospitalized with head trauma and fractures to both legs. The trusses were not banded or braced and were not secured to prevent sliding or falling from the roof. The limited size of the site and the presence of overhead power lines at the front of the house prevented the use of a crane.