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Oriented strand lumber

Oriented strand lumber (OSL) is a structural engineered wood product with consistent and predictable mechanical properties. It has high strength, high stiffness and dimensional stability. OSL also offers good fastener-holding strength.

A cross-section of a piece of oriented strand lumber  beside a cross-section of parallel strand lumber.
Comparison of oriented strand lumber (right) and parallel strand lumber (left).
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Common uses of OSL in construction include:

  • headers and beams
  • tall wall studs
  • rim boards
  • sill plates
  • millwork and window framing
  • decking for floors and roofs

Similar to laminated strand lumber (LSL), OSL comes from flaked wood strands that are long and thin. However, the wood strands in OSL are shorter than the wood strands in LSL. Combined with a structural adhesive, strands are oriented and formed into a large mat or billet and pressed.

OSL resembles oriented strand board (OSB) in appearance. Both products come from similar wood species and contain flaked wood strands. However, the wood strands in OSL are arranged in a parallel formation.

Technical information

OSL is a proprietary product. Specific engineering properties and sizes are unique to each manufacturer. As a result, OSL does not have common standards of production and design values.

Each producer develops their own engineering design values in accordance with the Canadian timber design standard (CSA O86). To ensure acceptance in the Canadian marketplace, manufacturers seek approval from the Canadian Construction Materials Centre (CCMC). Products approved by the CCMC receive an evaluation number as well as evaluation report, which includes engineering design values. These products are then listed in the CCMC’s registry of product assessments.

The manufacturer’s name / product identification and stress grade are usually marked on the material at various intervals. Any special cutting, notching or drilling should follow manufacturer recommendations. Manufacturers’ catalogues and evaluation reports are primary sources of information for design, installation details and performance characteristics.

OSL is one of many products used in mass timber construction projects across Canada.

For more information
Canadian Forest Service publications
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