What is Structural Composite Lumber (SCL)?

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Structural composite lumber (SCL) describes the family of engineered wood products manufactured using small, fast-growing, and underutilized trees.

SCL includes laminated veneer lumber (LCL), parallel strand lumber (PSL), laminated strand lumber (LSL), and oriented strand lumber (OSL).

Structural composite lumber is popular due to its product strength, reliability, availability, and consistency. 

This article explains the properties and advantages of SCL products in the construction industry.

Manufacturing Structural Composite Lumber (SCL)

SCL products are manufactured by layering graded and dried veneers, strands, or flakes with adhesives. This process creates billets that are cured in a heating press and are cut into the required dimensions. The grain of each layer or veneers or flakes used in SCL run primarily in the same direction. 

The typical depths of SCL members range from 241 to 606 mm. SCL is generally available in lengths of up to 20 m. 

SCL is manufactured at a low moisture content to reduce shrinkage after installation. Low moisture content in SCL prevents splitting or warping issues during its service.

SCL products are unique to each manufacturer. They do not have common standard production and design values. The design values of SCL products obtained from test results are analyzed in accordance with CSA 086 and ASTM D5456. The design values are reviewed and approved by the Canadian Construction Materials Centre.

Types of Structural Composite Lumber (SCL)

The different types of SCL products are:

1. Laminated veneer lumber (LVL): LVL is manufactured by bonding together rotary peeled or sliced thin wood veneers under heat and pressure. 
2. Laminated strand lumber (LSL): LSL is manufactured similar to LVL but using timber strands. LSL has low strength and stiffness properties compared to LVL.
3. Parallel strand lumber (PSL): PSL is produced by bonding together veneer strands under high pressure. The veneer strands are aligned parallel to increase strength.
4. Oriented strand lumber (OSL): OSL is similar to LSL, except it uses shorter veneer strands without compromising the length-to-thickness ratio. OSL is less strong and stiff compared to LVL or PSL. 

Advantages of Structural Composite Lumber (SCL)

1. SCL is three times stronger than regular lumber.
2. SCL is dimensionally stable, which reduces its chances of shrinking.
3. It is a solid, predictable, and uniform wood product used as an alternative to traditional lumber.
4. SCL can take higher loads compared to similarly-sized conventional lumber members.
5. SCL can be sawn to the desired size.
6. SCL does not use rejected pieces for production. Hence it is 100 percent reusable.

SCL is used for various applications like rafters, headers, truss chords, columns, beams, joists, I-joist flanges, wall studs, and formworks.

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