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STRENGTH, STRAIGHTER LENGTHS ENGINEERED WOOD PRODUCTS CONTINUE TO DELIVER THE GOODS BY JOHN G. SMITH
PHOTO: APA
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load of lumber could easily be considered one of the most flexible building products around. It can be transformed into everything from headers and studs to sills and joists. All it takes is a combination of the right tools, a few fasteners and a little know-how. As flexible as it may be, there is room to improve. Engineered wood products transform raw materials into something stronger and straighter than would ever be possible through milling alone. Where builders have been known to cull between 5 and 10% of a load of sawn lumber, depending on its quality, they might waste less than 2% of the engineered wood products that promise to be consistent from one piece to the next. “Some of these materials are going to be much more reliable,” says Ed Elias, the recently named president of the APA – Engineered Wood Association. “Contractors know how they are going to behave.” The products offer a classic example of something greater than its individual parts.
The adhesives and rectangular strands of wood used to make Oriented Strand Board (OSB), for example, eliminate worries about gaps and voids. Veneers, strands and flakes are combined with adhesives to make Structural Composite Lumber (SCL), creating consistent building blocks known as billets. These billets are used in products like Laminated Veneer Lumber (LVL) for headers and rafters, and Parallel Strand Lumber (PSL) to make heavily loaded columns or beams with unusually long spans. Twelve-inch strands of wood are combined to produce Laminated Strand Lumber (LSL), while shorter strands are used to make Oriented Strand Lumber (OSL), and the results are found in everything from headers and beams to rim boards and studs. The differences can be dramatic. A 9.5” I-joist, for example, can add about a foot to the potential span achieved with a sawn piece of 2x10 lumber. Pieces of Glued Laminated Timber, also known as glulam, come anywhere
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MARCH/APRIL 2014
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