SCL Basics
Structural composite lumber (SCL), which includes laminated veneer lumber (LVL), parallel strand lumber (PSL), laminated strand lumber (LSL) and oriented strand lumber (OSL), is a family of engineered wood products created by layering dried and graded wood veneers, strands or flakes with moisture-resistant adhesive into blocks of material known as billets, which are subsequently resawn into specified sizes. In SCL billets, the grain of each layer of veneer or flakes runs primarily in the same direction. The resulting products out-perform conventional lumber when either face- or edge-loaded. SCL is a solid, highly predictable and uniform engineered wood product that is sawn to consistent sizes and is virtually free from warping and splitting. A brief description of each product is
as follows:
Laminated Veneer Lumber (LVL)
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.
Parallel Strand Lumber (PSL)
PSL 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.
Laminated Strand Lumber (LSL)
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.
Oriented Strand Lumber (OSL)
Similar to 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.
White Paper: Code Requirements for Structural Composite Lumber
APA, AWC and WIJMA jointly developed this paper that describes the basic code recognition for structural composite lumber and the need for product certification in compliance with the codes.
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