Since the introduction of plywood and glued-laminated timber (glulam) beams more than a century ago, engineered wood has continuously progressed to provide greater strength, versatility, consistency, and many other attributes. Today, the engineered wood category encompasses oriented strand board (OSB), strand and fiber siding, laminated strand lumber (LSL) I-joists, laminated veneer lumber (LVL), and mass timber products. These building materials allow longer clear spans, greater energy efficiency, and faster, more economical construction. In commercial construction, four- and five-story wood office buildings are common, with the tallest wood buildings now reaching 20 stories.