APA - The Engineered Wood Association

Cross-Laminated Timber (CLT)

Cross-laminated timber (CLT)Cross-laminated timber (CLT) is a prefabricated solid engineered wood panel. Strong and lightweight, CLT is becoming increasingly popular as an alternative to conventional structural materials in multi-family and commercial construction. Photo courtesy of Nordic Engineered Wood.

CLT is made from three or more layers of solid-sawn lumber or structural composite lumber (SCL) that are orthogonally bonded together with structural adhesives to form a solid, straight rectangular-shaped panel. Stacking the layers crosswise (alternating layers, as illustrated in the drawing below) increases the structural and dimensional stability of the product. CLT is intended for use in wall, floor and roof applications in residential and non-residential buildings. The panels are available in a range of sizes and can be customized to fit specific needs.

CLT layers are stacked crosswise for increased dimensional stability

Although CLT has been used in Europe for more than a decade, the engineered wood product recently began garnering attention in North America as an alternative to concrete and steel in non-residential construction due to its multiple advantages, including:

  • Lower material weight at comparable strength to conventional structural materials
  • Dimensional stability with minimal shrinkage in building height
  • Panels span in both directions
  • Seismic performance
  • Versatility and ability to integrate with other materials
  • Prefabricated panels for easy installation and speedy construction
  • Low job site wastes
  • Green building

CLT is made from wood -- the world's most renewable, sustainable and environmentally friendly building product. Life cycle assessments have shown that, in cradle-to-grave comparisons, wood structures perform better than steel and concrete designs.

American National Standard for Cross-Laminated Timber

Walls constructed from CLTA new standard for CLT was approved by the American National Standards Institute (ANSI) and published by APA in December 2011, which was subsequently revised in 2012. ANSI/APA PRG 320-2012 Standard for Performance-Rated Cross-Laminated Timber provides requirements and test methods for qualification and quality assurance of CLT. The standard includes seven stress classes covering major wood species in North America.

Download a free PDF copy of ANSI/APA PRG 320-2012 from the APA Publications Library.