Cross-Laminated Timber (CLT) panels Fact Sheet - Overview, Standards, Materials, and Manufacturing Grades

Sep 15, 2026

Uploaded by Kurz

Cross-laminated timber (CLT) panels consist of lumber or composites layers stacked crosswise at 90° and bonded together, typically using an odd number of layers (three to seven, with some European production reaching nine). CLT was developed in central Europe in the early 1990s and serves as a structural or non-structural alternative for buildings worldwide. The material requires certified grading and ANSI/APA-PRG 320 compliance in North America, including kiln-dried lumber moisture targets. Manufacturing includes lumber qualification, finger-joint bonding, and approved grade layouts (E1–E5, V1–V5, S1–S3) with design values by layer count.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages7

Reading Time18 min

AccessFree to download

What are CLT panels?

History

North American Standard

Lumber requirements

CLT Panel Manufacturing

CLT panels grade and specification details

Design values of CLT panels based on grade and number of layers

Cross-Laminated Timber (CLT) panels Fact Sheet Authored by Henry Quesada, Professor and Extension Specialist; Sailesh Adhikari, Research Associate, and Robert Smith, professor. Department of Sustainable Biomaterials, Virginia Tech. What are CLT panels? CLT panels are comprised of lumber or compositeslayers with boards stacked crosswise at 90-degree angles and glue together. See Figure 1. An odd number of layers, three to seven per panel, is common to fabricate CLT panels. Some of the companies in Europe are manufacturing up to nine layers. Figure 1: Structural grade CLT layups. Source:(Fragiacomo et al. , 2012) History CLT was invented in the early 1990s in central Europe and is now considered an alternative construction material to mid and high-rise buildings across the globe. Based on uses, CLT panels are two types: structural or non-structural. Structural CLT panels are used in structural construction and manufactured under the criteria specified by APAPRG 320 standard in North America. However, nonstructural CLTs can be manufactured from any lumber species and types that satisfy the user requirements. Non-structural CLT panels are commonly used as access mats as an alternative to bolted mats. Table 1 shows a list ofCLT manufacturing facilities in the USA. Table 1 : List of CLT manufacturers in the US | Company Name | City | State | Products | | --- | --- | --- | --- | | DR Johnson | Riddle | OR | All CLTs | | SmartLAM | Columbia Falls | MT | All CLTs | | SmartLAM | Dothan | AL | All CLTs | | Freres
Lumber | Lyons | OR | All CLTs | | Sterling | Phoenix | IL | CLT Mats only | | Sterling | Lufkin | TX | CLT Mats only | | Spartan Mat | Peach
Bottom | PA | CLT Mats only | | Structurlam | Conway | AR | All CLTs | | Mercer Mass Timber | Spokane Valley | WA | All CLTs | | Vaagen
Timbers | Colville | WA | All CLTs | | Texas CLT | Magnolia | AR | All CLTs | | Viking Mat
Company | Eden Prairie | MN | CLT Mats only | | Yak Mat | Columbia Falls | MS | CLT Mats only | North American Standard In North America, CLT mills only qualify to produce CLT panels for structural applications after getting certified through the ANSI/APA-PRG 320 standard. The Engineered Wood Association grants the qualification, and each mill should certify both process and product for commercial production of CLT panels for structural application. Lumber requirements Sawn lumber for CLT manufacturing must be from softwood species with a specific gravity greater than 0.35. The American Lumber Standards Committee (ALSC) must qualify softwood species under PS 20 for manufacturing structural CLT panels. Lumber tobe used in CLT manufacturing must be kiln-dried toa moisture content of 12±3% . Cross-laminated timber layers parallel to the outside layer must be a minimum of visually graded Number 2 and visually graded Number 3 for the perpendicular layers. The thickness of individual lumber must be 15.9 mm to 50.8 mm. The common lumber choice is 60.96 mm to 241.3 mm in width. Table 2 shows the approved CLT layouts and Table 3 lists the technical specifications of each approved CLT grade in the ANSI/APA-PRG 320 standard. CLT Panel Manufacturing Figure 2: Fingered jointed lumber. The production process of the CLT panels starts with a quality check of the available lumber regarding sizes, moisture content, and lumber grade. First, the lumber is bonded lengthwise using finger joints (Figure 2) . Table 2: CLT panels grade and specification details | CLT
Grades | Specification details. | | --- | --- | | E1 | 1950f-1 .7E Machine Strength Rated (MSR) Spruce-Pine-Fir (SPF) in all parallel layers and No. 3 SPF in all perpendicular layers | | E2 | 1650f-1 .5E MSR Douglas Fir-Larch lumber in all parallel layers and No.
3 Douglas Fir-Larch lumber in all perpendicular layers | | E3 | 1200f-12E MSR, Northern Species, Eastern Softwoods or Western Woods in all parallel layers and No.
3, Northern Species, Eastern Softwoods or Wes

FAQs

What are CLT panels and how are they constructed?

CLT panels are made by stacking lumber or composite boards crosswise at 90° and gluing them together. An odd number of layers, commonly three to seven, is typical for fabricating CLT panels.

How does the North American standard affect structural CLT production?

In North America, mills must qualify to produce CLT panels for structural applications after certification through the ANSI/APA-PRG 320 standard. The Engineered Wood Association grants qualification, and each mill must certify both process and product.

What lumber and grading requirements are needed for manufacturing CLT?

CLT manufacturing uses softwood species with specific gravity greater than 0.35, and the species must be qualified under PS 20 for structural CLT. Lumber must be kiln-dried to 12±3% moisture, and outer and perpendicular layers require specified visual grades.

Sep 15, 2026

Uploaded by Kurz