The technologies applied to wood and the use of wood have evolved with man and society. Wood was initially an indigenous building material and has evolved into products delivered worldwide.
Wood has amazing natural qualities that lend itself to many functions. It is resilient, sustainable, and stores carbon in its creation. It can be formed into different shapes, joined to create a durable shape, treated to endure biological attack and more.
Some point to the late 1940’s and early 1950’s as lumber standards evolved and changed how and what we buy from lumber yards. In the 1970’s joists were developed using plywood webs and lumber chords to produce longer material with greater load-bearing capacity and dimensional stability. Today, engineered wood is a dominant force in wood frame construction – Structural composite lumber (SCL), a term used to encompass the family of engineered wood products that includes laminated veneer lumber (LVL), parallel strand lumber (PSL), laminated strand lumber (LSL) and oriented strand lumber (OSL). The following is courtesy of APA-The Engineered Wood Association.
- LVL (laminated veneer lumber) LVL is a widely used structural composite lumber product. It is produced by bonding thin wood veneers together in a large billet so that the grain of all veneers is parallel to the long direction. The LVL billet is then sawn to desired dimensions depending on the end-use application. Because LVL is made with scarfed or lapped jointed veneers, LVL is available in lengths far beyond conventional lumber lengths. Popular LVL applications include headers and beams, hip and valley rafters, scaffold planking, and the flange material for prefabricated wood I-joists.
- PSL (parallel strand lumber) is manufactured from veneers clipped into long strands laid in parallel formation and bonded together with an adhesive to form the finished structural section. The length-to-thickness ratio of the strands in PSL is around 300. Like LVL and glulam, this product is used for beam and header applications where high bending strength is needed. PSL is also frequently used as load-bearing columns.
- LSL (Laminated Strand Lumber) Similar to PSL, laminated strand lumber is made from flaked wood strands that have a length-to-thickness ratio of approximately 150. Combined with an adhesive, the strands are oriented and formed into a large mat or billet and pressed. LSL is used in a variety of applications from studs to millwork components.
- OSL (Oriented Strand Lumber) — Like LSL, oriented strand lumber is also made from flaked wood strands. The strand geometry for OSL results in length-to-thickness ratios of approximately 75. Combined with an adhesive, the strands are oriented and formed into a large mat or billet and pressed. OSL is used in a variety of applications from studs to millwork components.
While engineered lumber and components are commonplace on today’s construction sites, a new technology is arriving from Europe. Over the last decade or two, European manufacturers have developed a processed referred to as cross-laminated timber. The posts to this page provide the latest information about this phenom.