originally comprised of a vertical piece of plywood between two solid wood flanges in the shape of an I. Its popularity (in the 1970s) was due to growing interest in open plan building designs that required long unsupported joist spans. I-joists are also very useful in framing cathedral ceilings (Fisette, 2000). By 1977, the Trus-joists solid wood components were replaced with laminated veneer lumber (LVL), which looks like plywood but whose laminations run in the same direction. Around 1990, the joists plywood web was replaced with oriented strand board (OSB). Today, I-joists have been joined by boards and beams of laminated strand lumber (LSL), glue laminated timber (glulams), parallel strand lumber (PSL), and laminated veneer lumber (LVL) for a wide variety of uses (Gibson, 2002).