Structural Composite Lumber (SCL):<br>A Practical Alternative

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Structural Composite Lumber (SCL):
A Practical Alternative

Structural Composite Lumber (SCL) is a family of solid, highly predictable and uniform engineered wood products designed for structural use. SCL is created by layering dried and graded wood veneers, strands or flakes with exterior type adhesives into blocks of material known as billets. The billets are cured in a heated press and sawn to consistent sizes that are easily worked in the field using conventional construction tools.

SCL products include laminated veneer lumber (LVL), parallel strand lumber (PSL), laminated strand lumber (LSL) and oriented strand lumber (OSL). These products are commonly used in the same structural applications as conventional sawn lumber and timber, including rafters, headers, beams, joists, rim boards, studs and columns. SCL products are also used for wood I-joist flanges and truss chords.

Strong, Reliable and Consistent

Virtually free from warping, splitting and shrinking, SCL products out-perform conventional lumber when either face- or edge-loaded. SCL is generally manufactured with the grain of each layer of veneers, strands or flakes oriented parallel to the length of the billet. Because the grade and quality of each individual layer can be closely controlled, variations in product properties are lower than in conventional sawn lumber products. As a result, the properties and performance of SCL can be more confidently predicted.

Making the Best Use of Resources

The manufacture of SCL represents an efficient utilization of wood resources. Large SCL billets are produced from a variety of tree species, including species that are relatively small, underutilized, fast-growing, and sometimes considered low-grade.

Allowable Strength Properties

Structural properties of SCL are evaluated using methods specified in ASTM D 5456, Standard Specification for Evaluation of Structural Composite Lumber Products. The structural design values for SCL are published on a proprietary basis by manufacturers of SCL and are typically recognized in evaluation reports published by the ICC ES and Product Reports issued by APA.

The APA Mark of Quality

APA trademarks appear only on products manufactured by APA member mills. The mark signifies that the product quality is subject to verification through APA audit – a procedure designed to assure manufacture in conformance with APA performance standards or the standard shown in the mark.

SCL Products

Laminated Veneer Lumber (LVL)
LVL is the most widely used SCL product. It is produced by bonding thin wood veneers together in a large billet. The grain of all veneers is parallel to the long direction. The LVL billet is then sawn to desired dimensions depending on the construction application. The resulting product features enhanced mechanical properties and dimensional stability that offer a broader range in product width, depth and length than conventional lumber. The many uses of LVL include headers and beams, hip and valley rafters, rim board, scaffold planking, studs, flange material for prefabricated wood I-joists, and truss chords.

Parallel Strand Lumber (PSL)
PSL consists of long veneer strands laid in parallel formation and bonded together with an adhesive to form the finished structural section. PSL is commonly used for long-span beams, heavily loaded columns, and beam and header applications where high bending strength is needed.

Laminated Strand Lumber (LSL) & Oriented Strand Lumber (OSL)
Similar to PSL, LSL and OSL are manufactured from flaked wood strands that have a high length-to-thickness ratio. The primary difference between them is that the length of strand used in OSL is shorter (up to 6 inches) than that used in LSL (approximately 12 inches). Combined with an adhesive, the strands are oriented and formed into a large mat or billet and pressed. Although LSL and OSL generally have somewhat lower strength and stiffness properties than LVL and PSL, these products offer good fastener-holding strength and mechanical connector performance. LSL and OSL are commonly used in a variety of applications, such as beams, headers, studs, rim boards, and millwork components.

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APA Engineered Wood Construction Guide: PDF 13.8MB

Product Manufacturers (Structural Composite Lumber)

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Structural Composite Lumber (SCL):A Practical Alternative