I-joists are made by gluing solid sawn lumber or laminated veneer lumber (LVL) flanges to a web made of plywood or oriented strand board (OSB). I-joists exhibit uniform stiffness, strength and are lightweight.

The availability of wood I-joists used as floor joists and as deep, roof joists that allow for extra insulation has made them popular.  They are also an economical alternative to open web steel joists.

Wood I-joists are manufactured in a variety of sizes. Long lengths have finger-jointed flanges. Butt jointing or toothed, tongue-and-groove or scarf configurations are used to splice the webs.