Engineered wood products: glulam, CLT, LVL, LSL, PSL, I-joists

One-line orientation

Engineered wood products differ by what they’re built from (lumber, veneers, or strands) and how the layers are oriented (parallel vs cross) — and the CLT-vs-glulam and LVL-vs-PSL pairs are the classic distractors.

Key points

• Glulam (glue-laminated timber): dimensional lumber layers bonded with moisture-resistant adhesive, grain parallel. → beams, columns, arches; long spans; needs moisture protection; costlier than sawn lumber.
• CLT (cross-laminated timber): solid-sawn lumber layers glued perpendicular to each other. → floor/wall/roof panels in multi-story / mass-timber buildings; high strength, good thermal performance, fast install.
• LVL (laminated veneer lumber): multiple veneer (sheet) layers bonded parallel. → beams, headers, edge-forming; high strength, long spans.
• LSL (laminated strand lumber): parallel wood strands bonded. → headers, beams, studs, rim boards; consistent, less prone to warp; moisture-sensitive.
• OSL (oriented strand lumber): structural composite lumber used for members such as rim boards and short-span headers.
• OSB (oriented strand board): the sheet-panel product used for wall sheathing, subflooring, and roof decking.
• PSL (parallel strand lumber): long, thin strands bonded for high density/strength. → beams, columns, high-load applications; high cost, limited availability.
• Wood I-joist: I-beam with LVL or solid-wood flanges and an OSB or plywood web. → floor and roof joists; lightweight, strong, long spans, resists warping; vulnerable to moisture and fire.

Engineered wood — the ingredient and its direction name the product

Start with the physical makeup: boards, veneers, strands, or a flange-and-web composite.

View diagram Hide diagram 2 panels

2 panels side by side — swipe to compare →

Key

• blue cross-layer = orientation changes

Confusions / comparison

Product	Built from	Layer orientation	Typical form / use
Glulam	Dimensional lumber	Parallel	Beams, columns, arches
CLT	Solid-sawn lumber	Perpendicular (cross)	Panels — floors, walls, roofs
LVL	Veneer sheets	Parallel	Beams, headers
LSL	Long parallel strands	Parallel	Headers, beams, studs, rim board
OSL	Oriented strands	Structural lumber member	Rim boards, short-span headers
OSB	Oriented strands	Sheet panel	Sheathing, subflooring, roof decking
PSL	Long thin strands	Parallel	Heavy beams/columns, high load
I-joist	LVL/solid flange + OSB/ply web	Composite	Floor/roof joists

Related

→ Sheathing and non-veneer boards (this topic): plywood/OSB panels vs these structural members · Wood structure and shrinkage (this topic): why cross-lamination cancels directional movement · Lumber sizing and defects (this topic): the solid-lumber problems EWPs are engineered around.