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Certification Mark Acceptance for Mass Timber Products

Glued laminated timber (glulam) has been used in heavy timber construction for decades, while cross-laminated timber (CLT) is a product innovation that began in Europe and is now enabling the wave of tall timber buildings in North America. These two products are part of what is now referred to as “mass timber” and each has its own product manufacturing standard.

In the US, glulam is manufactured to ANSI A190.1, Standard for Structural Glued Laminated Timber. Its companion standard in Canada is CSA O177, Qualification Code for Manufacturers of Structural Glued-Laminated Timber. While there are some differences between these two standards, the differences are minor.

The CLT standard is ANSI/APA PRG 320, Standard for Performance-Rated Cross-Laminated Timber, which is recognized in the US and Canada. There has been some confusion that because “APA” is contained in the name of the CLT standard—and knowing that APA-The Engineered Wood Association is recognized as a third-party agency—that CLT products must be certified by APA. That is incorrect, since the PRG 320 standard states that any qualified certification, inspection, and/or testing agency that is accredited under the relevant ISO/IEC standards can certify, inspect, and/or test CLT products. “APA” is in the name of the CLT standard because APA functions as the ANSI Standards Development Organization for the standard and is not related to their accreditation as a third-party agency.

PFS TECO maintains accreditations in the United States through the International Accreditation Service (IAS) and in Canada through the Standards Council of Canada (SCC), having demonstrated compliance with the ISO/IEC standards that cover certification, inspection, and testing:

  • ISO/IEC 17020, Requirements for the operation of varies bodies performing inspection;
  • ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories; and
  • ISO/IEC 17065, Requirements for bodies certifying products, processes and services.

Copies of our accreditation certificates as a recognized Inspection Agency (AA-652) and Test Laboratories (TL-109 for Wisconsin and TL-207 for Oregon) can be downloaded from the IAS website at A copy of our accreditation certificate as a recognized certification body can be downloaded from the SCC website at

You may also refer to the PFS TECO accreditation page which contains links to these documents.

Consequently, glulam or CLT products with a gradestamp that includes the PFS Checkmark or TECO TESTED® certification marks (like that shown below for a CLT gradestamp certified to ANSI/APA PRG 320) are recognized as complying with the requirements of the particular product standard. While there may be differences between products manufactured by different companies, all that is required for certification is that the products be certified by an accredited and recognized third-party agency.

Manufacturer Name

Mill 000
PRG 320
4-1/8 IN

It is therefore suggested that architects, engineers and designers who specify glulam or CLT for their construction projects should specify the products by species and/or grade in accordance with ANSI A190.1 (for glulam) and ANSI/APA PRG 320 (for CLT), and not specify that products be certified by a particular certification agency. Specifying either product certified by a particular certification agency only serves to limit the products available to the building contractor and may cause unnecessary project delays.


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