Parallel Strand Lumber (PSL)
Parallel Strand Lumber (PSL) is an engineered wood product made by bonding long, thin strands of wood veneer together under heat and pressure, with all strands oriented parallel to the length. PSL is used for heavy-duty beams, headers, and columns where high strength and stiffness are required.
In Detail
PSL is manufactured by clipping Douglas fir or southern yellow pine veneer into strands approximately 1/2" wide, 1/8" thick, and up to 8 feet long. These strands are coated with waterproof adhesive and fed into a continuous press where they are compacted under high pressure and microwave-cured. The result is a dense, strong material with a distinctive straw-like appearance.
The parallel orientation of the strands gives PSL its high strength and stiffness — it typically has a modulus of elasticity (MOE) of 2.0E, making it one of the stiffest engineered lumber products available. PSL is the premium choice when deflection control is critical, such as long-span headers over large openings or beams supporting concentrated loads.
PSL is manufactured by Weyerhaeuser under the Parallam brand name. Standard column sizes are 3-1/2" x 3-1/2", 5-1/4" x 5-1/4", and 7" x 7". Beam sizes range from 3-1/2" x 9-1/4" up to 7" x 18". PSL is more expensive than LVL or glulam but offers superior performance for demanding structural applications.
Related Terms
Laminated Veneer Lumber (LVL)
Laminated Veneer Lumber (LVL) is an engineered wood product made by bonding thin wood veneers together with all grain running parallel, creating a beam material that is stronger, straighter, and more dimensionally stable than solid sawn lumber of the same size.
Glulam (Glue-Laminated Timber)
Glulam (glue-laminated timber) is an engineered wood product made by bonding layers of dimensional lumber together with structural adhesive to create large beams, arches, and columns. Glulam combines the strength of engineered wood with the appearance of natural timber.
Modulus of Elasticity (MOE)
Modulus of Elasticity (MOE) is a measure of a material stiffness — how much it resists bending under load. In lumber and engineered wood, MOE is expressed in millions of pounds per square inch (psi) and determines how far a beam or joist will deflect under a given load. Higher MOE means less deflection.
Related Materials
PSL (Parallel Strand Lumber)
Parallel strand lumber (PSL) is a high-strength engineered wood product made from long, thin strands of wood veneer bonded with waterproof adhesive under high pressure. Known commercially as Parallam PSL (Weyerhaeuser), it is used for beams, columns, and posts where maximum load-carrying capacity is required.
LVL (Laminated Veneer Lumber)
Laminated veneer lumber (LVL) is a high-strength engineered wood product made from thin wood veneers bonded with structural adhesive under heat and pressure. It is the most commonly specified engineered beam and header material in residential and light commercial construction.