Engineered Lumber Outperforms Sawn Lumber in Many Applications
Traditional sawn lumber has natural limitations: knots, grain variation, moisture content changes, and maximum available sizes constrained by the dimensions of logs. Engineered lumber products overcome these limitations by manufacturing structural members from wood fibers, veneers, or strands bonded with adhesives under controlled conditions. The result is more predictable structural performance, larger available sizes, and better dimensional stability. The ARE PPD tests engineered lumber because these products appear in virtually every contemporary light-frame and mass timber project.
Laminated Veneer Lumber (LVL)
LVL is made by bonding thin wood veneers (about 1/10 inch thick) with all grain running parallel to the long axis of the member. The manufacturing process produces a highly consistent structural member with no knots in the critical cross-section. LVL is available in standard thicknesses of 1-3/4 inches (multiple plies can be fastened together for wider beams) and depths ranging from 5-1/2 inches to 24 inches or more. LVL is used for headers over openings, long-span beams, ridge beams, hip and valley rafters, and any application where a sawn lumber beam would be inadequate. LVL has higher allowable bending stress than comparable sawn lumber.
Parallel Strand Lumber (PSL)
PSL is made from strands of wood fiber (typically 8 inches long) oriented parallel to the member axis and bonded under heat and pressure. The result is a dense, heavy member with excellent bending strength and stiffness. PSL is commonly used for large columns and posts, heavily loaded beams, and transfer girders. It is denser and heavier than LVL, which makes it more suitable for posts and columns where compressive strength is critical.
Laminated Strand Lumber (LSL) and Oriented Strand Lumber (OSL)
LSL and OSL are made from shorter wood strands bonded together. They are generally less strong than LVL or PSL but are cost-effective for studs, rim boards, and blocking applications where the highest performance is not required. They offer excellent dimensional stability and are widely used as rim boards in floor framing.
Glued Laminated Timber (Glulam)
Glulam is manufactured by laminating dimension lumber boards (typically 1-1/2 inch thick) with adhesive, with grain running parallel to the member length. Glulam is used for large beams, arches, and curved structural members that cannot be produced in solid sawn lumber. It can be manufactured in custom sizes and curved configurations, making it popular for exposed structural applications in churches, sports facilities, and assembly buildings. Glulam's combination of structural performance and aesthetic appeal makes it unique among structural materials.
Cross-Laminated Timber (CLT)
CLT is a mass timber product consisting of layers of dimension lumber boards stacked perpendicular to each other and bonded with adhesive - similar in concept to plywood but using solid lumber boards. CLT panels can be used as walls, floors, and roofs, carrying loads in two directions (unlike glulam, which is a one-directional beam). CLT is driving the mass timber movement, enabling multi-story wood buildings previously impossible with light-frame systems.
Key Exam Points
- LVL: veneers, parallel grain, high strength, standard sizes, used for beams and headers.
- PSL: strands, dense, excellent for columns and heavy beams.
- Glulam: laminated boards, custom sizes, curved configurations possible.
- CLT: cross-laminated panels, two-way structural capacity, enables mass timber buildings.
- All engineered lumber has more predictable performance than sawn lumber due to manufacturing controls.
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