Fire performance of mass timber construction: continuous testing confirms their fire safety attributes

Over the past decade, cross-laminated timber (CLT) has been increasingly used in numerous buildings in Canada. Other mass timber products are also being used and developed, allowing designers to choose materials from a broad range of products. However, fire performance remains one of the attributes of these systems that is of concern to many potential occupants or owners of these buildings, not to mention building officials and fire departments.

2019 update of the fire performance chapter in the Canadian CLT Handbook

Since the publication of its first edition of the Canadian CLT Handbook, in 2011, FPInnovations has carried out many tests and research projects to increase our knowledge of CLT and its performance with regards to fire safety in mass timber buildings, and to update codes and standards.

These results are now available in the recent Fire performance of cross-laminated timber assemblies, published as part of the 2019 edition of the Canadian CLT Handbook. This document provides the most up-to-date information related to fire performance attributes of CLT elements conforming to the bi-national product manufacturing standard ANSI/APA PRG 320.

The results have shown that CLT elements, with or without gypsum board protection, can achieve significant fire resistance, beyond 3 hours in some cases. Tests have also shown that fire stops approved for concrete construction are suitable for CLT elements, so long as adequate detailing is provided.

To learn how to get your copy of the Canadian CLT Handbook, visit

New tests on heat delamination of adhesives

FPInnovations has extended its research to various aspects of fire behaviour of wood buildings and, in that respect, has undertaken new tests to validate the charring rate of CLT elements manufactured with adhesives fulfilling new mandatory requirements, which were based on our previous findings and recommendations made to update the 2018 edition of ANSI/APA PRG 320.

So far, results suggest that CLT manufactured with an adhesive meeting these new requirements could use the commonly-accepted one-dimensional charring rate of 0.65 mm/min throughout the fire exposure, regardless of the position of the first bond line. Results of room fire tests conducted by National Research Council Canada also showed that compartments made of CLT elements manufactured with non-delaminating adhesives eventually reached burned-out of the fuel content in several tests, leading to self-extinguishment. FPInnovations initiated a change proposal to CSA O86 in January 2020 for revising the applicable charring rate for CLT elements.

Other mass timber assemblies 

With the increasing interest to expand the use of other mass timber assemblies into modern larger and taller wood buildings, FPInnovations has also performed research studies on fire performance of other types of mass timber assemblies that led to the publication of several reports. These studies evaluated the fire performance of nail-laminated timber (NLT or Nail Lam), dowel-laminated timber (DLT), Glue-laminated timber decks (GLT) and cross-laminated veneer lumber (X-LVL).

These reports showcase the latest findings with regards to fire performance of these other mass timber products. This research will support designers and builders in the use of mass timber assemblies, by ensuring fire safe designs. 

Research continues with regards to fire performance of mass timber assemblies. For more information on fire research, contact Christian Dagenais – Lead Scientist or Lindsay Ranger – Scientist in the Building Systems group at FPInnovations. 

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