How to Set Floor Trusses

Layout the sill plates of your foundation by measuring off of one end in 16-inch increments and placing an "X" on the mark. Drop back 1 3/4 inches and place a mark. This represents the outside edge of the truss---trusses are framed from 2 by 4 lumber, which is 3 1/2 inches, so half of that is 1 3/4 inches---and the "X" represents the center of the truss.

Set the trusses on each end of your foundation and attach them into the treated foundation sill with 16 penny nails.

Pull a string across one end of the trusses as they rest on the foundation sill.This string will represent a straight line by which all other trusses will be set.

Continue to set the remainder of the trusses by aligning them with the reference string and placing them on the pencil marks placed on the foundation sill. The trusses may not stand up square after they are attached to the sill plate of the foundation. However, you will correct this by attaching plywood to the exterior of the trusses around the perimeter.

Cut plywood strips that are as wide as the trusses are wide. Cut the strips from an 8-foot sheet of plywood. For example, if your trusses stand 16 inches proud of the foundation, measure 16 inches across an 8 foot sheet of 3/4-inch plywood and snap a chalk line along the length. Use a circular saw to rip the plywood strips. Attach the strips to the ends of the trusses, fully connecting the trusses together along the perimeter of the foundation sill. Begin from one end, squaring the end truss with the foundation sill. Using a speed square to place on the foundation sill and up the floor truss will ensure that the truss is straight and plumb. Make sure to butt the plywood joints in the center of each truss at the end of your 8-foot run. Attach the plywood using 8 penny nails.