New research confirms mass timber's fire safety for taller buildings

The middle room on the second story had an exposed mass timber back wall, ceiling and floor. A fire was started in the garbage can to represent a potential construction fire scenario, which started to spread along the ceiling of the compartment. The fire scenario took 20 minutes to develop allowing for time for occupants to leave or extinguish the smaller fire. Approximate time after ignition: 21:30 minutes. Flashover occurred within the compartment causing ignition of the exposed mass timber. The fire died down after one minute of burning. (Approximate time after ignition: 23:30 minutes.)

Photo By Canadian Wood Council

OTTAWA, Ontario — Results from some of the most extensive fire testing of large-scale, mass timber construction marks a "significant milestone in the advancement of mass timber construction."

The findings, compiled in a comprehensive 121-page report titled, "Large-Scale Fire Tests of a Mass Timber Building Structure for MTDFTP (Mass Timber Demonstration Fire Test Program)," showed that in severe, "unsprinkled" fire conditions with exposed structural mass timber, the test structure remained stable and solid after enduring five different fire tests of varying severity and duration, with an overall incremental total of 19 hours of fire exposure. 

“We are very pleased by the report findings, which solidify the position of mass timber as a safe construction material,” said Robert Jonkman, P.Eng., Vice President of Codes and Engineering at Canada Wood Council. “This scientific proof of mass timber’s exceptional structural fire performance helps address concerns about its suitability for use in larger and taller building applications."

Led by the CWC, and in partnership with industry associations, federal and provincial government agencies, and fire safety and engineering consultants, the Mass Timber Demonstration Fire Test Program was developed to demonstrate the performance of mass timber construction under severe fire conditions. 

The goal of the program is to create and disseminate fire performance data to construction sector stakeholders and building and fire safety regulators to inform market acceptance of larger and taller mass timber buildings in Canada. 

The report lays out the findings from a series of five separate fire research full-scale experiments conducted by the NRC as part of the Program in the summer of 2022. The experiments were conducted within a full-scale, 2-story, 334 square-meter mass timber structure at NRCan's Canadian Explosives Research Laboratory (CERL) in Ottawa.

This was the largest mass timber fire test conducted in Canada to date. These fire tests were conducted without sprinklers and firefighting intervention for extended hours.

The findings also support the CWC’s ongoing work in codes and standards which they will use to help inform modern building codes which are evidence-based and are regularly updated to keep pace with advancements in innovative construction technologies.

As a result of this extensive project, new scientific data were gathered on the fire performance of mass timber in an open-plan office, the fire performance of mass timber in residential buildings, the fire performance of mass timber during construction, and the influence of exposed mass timber on fire severity and duration. These data and the resulting knowledge outcomes can be used by stakeholders to:

  • assist in the fire safety design, evaluation, and approval of alternative solutions for tall and large mass timber buildings;
  • develop firefighting strategies for construction sites and finished buildings using mass timber; and
  • inform code development pertinent to mass timber construction.

These comprehensive research tests examined the fire performance of both exposed and encapsulated (gypsum board-protected) mass timber in highly challenging fire scenarios. These valuable data will help inform technical committees when they review code change proposals developed by the CWC seeking to enable designers to leave a certain percentage of mass timber surfaces exposed in a building of Encapsulated Mass Timber Construction (EMTC).

"This marks a significant milestone in the advancement of mass timber construction," Jonkman concluded. "Apart from the evident benefits in terms of reduced construction schedules, environmental sustainability, and fire safety that project teams are already experiencing with EMTC
construction, they will now have the added advantage of offering building occupants enhanced aesthetics. Moreover, the documented positive impacts on health and well-being, attributed to the incorporation of natural materials like exposed mass timber in indoor environments, will significantly enhance the overall benefits experienced by building occupants.”

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Larry Adams | Editor

Larry Adams is a Chicago-based writer and editor who writes about how things get done. A former wire service and community newspaper reporter, Larry is an award-winning writer with more than three decades of experience. In addition to writing about woodworking, he has covered science, metrology, metalworking, industrial design, quality control, imaging, Swiss and micromanufacturing . He was previously a Tabbie Award winner for his coverage of nano-based coatings technology for the automotive industry. Larry volunteers for the historic preservation group, the Kalo Foundation/Ianelli Studios, and the science-based group, Chicago Council on Science and Technology (C2ST).