Abstract: EMPLOYEE #1 AND THREE OTHER EMPLOYEES WERE INSTALLING PRE-FABRICATED WOOD ROOF TRUSSES AT A SINGLE STORY HOUSE UNDER CONSTRUCTION . EMPLOYEE #1 WAS STANDING ON THE BOTTOM CHORD NEAR THE CENTER LINE OF THE SOUTHERN-MOST TRUSS AS THE WORKERS WERE ALIGNING THE TRUSS IN PEPARATION FOR SECURING IT IN PLACE. THE TRUSS SIMULTANEOUSLY BROKE IN TWO PLACES, CAUSING EMPLOYEE #1 TO FALL TO A CEMENT FLOOR SURFACE 10 FEET BELOW. EMPLOYEE #1 SUSTAINED MULTIPLE FATAL INJURIES, INCLUDING A CONCUSSION. ACCORDING TO OBSERVERS AT THE SCENE THE BOTTOM CHORD OF THE TRUSS HAD A LARGE DOUBLE KNOT ON ONE SIDE OF THE CENTER LINE AND AN INADEQUATELY SECURED GANG NAIL PLATE AT THE CENTER LINE. THESE FLAWS CAUSED THE BOTTOM CHORD TO BREAK AT THOSE LOCATIONS AS SOON AS WEIGHT WAS ADDED. A MISSING BEARING WALL, WHICH WOULD HAVE SUPPORTED THE TRUSS, ALSO CONTRIBUTED TO THIS ACCIDENT.