Structural Composite Lumber

LVL, PSL, and LSL/OSL

The concern for environmentally responsible building practices and the ongoing demand for better-quality structural materials have led to the increased reliance on a variety of engineered-wood products known as structural composite lumber, also referred to in the industry as SCL. These composite products are sought after because they are stronger, straighter, more uniform, and more dimensionally stable than sawn lumber. SCL is also environmentally friendly because it can be manufactured from small-diameter, fast-growing trees and mill scraps that would otherwise go to waste.

LVLs are easy to work with

Made from plies of wood veneer, much like plywood, LVLs are versatile. They can be used as beams, headers, and stair stringers (see FHB #170, p. 68). Smaller-dimension LVLs often are ganged together to create built-up beams, making them a convenient alternative to other products that are available only in large, single pieces. LVLs have a few disadvantages, though. They’re susceptible to cupping, so they shouldn’t be exposed to extremely moist conditions. They also are slippery and have sharp corners, so they need to be handled with care.

PSL is very heavy but very strong

Available in sizes up to 60 ft. long, 18 in. deep, and 7 in. wide, parallel-strand lumber (PSL) beams lead the pack in terms of size and strength. PSL is used most often as beam material, but it also is used for load-bearing columns. Pressure-treated PSL is available for use in decks, porches, and other outdoor projects. Unlike other SCL products, PSL has a distinctive look when left exposed and accepts stain well.

LSL and OSL are similar

Laminated-strand lumber (LSL) and oriented-strand lumber (OSL) aren’t as strong as PSL or LVL, so they’re most commonly used as rim board, studs, and short headers.

The main difference between these two materials has to do with the way they are manufactured. LSL is made with strips of wood, up to 13 in. long. OSL is manufactured with wood strands that are only as long as 6 in.

Photos by Krysta S. Doerfler

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