Engineered joists and rafters, which have a cross section akin to an I-beam, present a wrinkle to the carpenter crosscutting them with a circular saw. Because the plane of the web lies below that of the thicker chords, the saw can’t glide across an unbroken surface as it makes a cut.
To make a template for cutting these materials, I start by ripping about 3 ft. of 5/8-in. or 3/4-in. plywood or oriented strand board to a width slightly less than that of the web. This piece should fit easily on the web between two chords, creating a flush surface across the I-joist.
Next, I make a square cut on one end of the stock and mark my rafter’s plumb cut a foot or so back from the square cut. This step divides the stock into two unequal parts, A and B, as shown at the top of the drawing. After cutting along the mark, I then screw or nail part B to the top of part A. The saw’s table rides along the edge of the top piece, guiding the cut. The bottom piece supports the saw’s table. The bottom piece is longer than the top, so the first cut that you make also trims part A. That will allow you to register the edge of the template against the cut mark for accurate positioning. Finish the template by screwing a 1×2 handle to one of its edges.
Larry Haun, Coos Bay, OR
