Parallel strand lumber (PSL) is a high-strength structural composite marketed under the trade name Parallam®. PSL is comparable in strength to laminated veneer lumber. Both products are often grouped under the heading Structural Composite Lumber (SCL).

PSL is made from long strands of wood chopped from wood veneer. This process allows the removal of growth defects from the raw material. PSL is then made into large billets and sawn into stock and custom sizes.

Because it is a glued-manufactured product, PSL can be made in long lengths but is usually limited to 66 ft. (20 m.) because of transportation constraints. Manufactured at a moisture content of 11 percent, which is approximately the equilibrium moisture content of wood in most service conditions, PSL is less prone to shrinking, warping, cupping, bowing or splitting.

PSL is manufactured in the U.S. from Southern pine as well as other species and from Douglas fir in Canada. PSL has consistent properties and a high load carrying ability.

Applications  

PSL is well suited for use as beams and columns for post-and- beam construction, and for beams, headers, and lintels for light framing construction. It is used for large members in residential construction and as intermediate and large members in commercial building construction.

Because PSL is attractive it can be used where finished appearance is important.

Sizes

PSL stock sizes are compatible with established wood framing materials and dimensions. PSL beams are sold in thicknesses of 1-3/4" (45mm), 2-11/16" (68mm), 3-1/2" (89mm), 5-1/4" (133mm) and 7" (178mm). The smaller beams can be used individually as single plies or can be combined for multi-ply applications.

Although it can be sawn to any dimension, its economy is maximized in uses where light to medium steel sections are practical. High design values, a multitude of cross sections, and long lengths permit flexibility in overall building design.

Quality Control

The PSL manufacturing process includes tight controls on the raw material, assembly, and finishing properties. Because the manufacturing process removes strength-reducing defects from the wood strands, checking for consistent density in the finished product is the main quality control procedure.

Tips

General guidelines for PSL:

• Determine the load capacity.
  
• Select the size of the PSL member to meet the required load capacity.
  
• Ask the local distributor for technical literature.
  
• Determine if PSL members will be directly exposed to weather, high temperature or humidity. If so, consult with the manufacturer for information about preservative treatment.