Fire Resistance of Mass Timber: Insights from Research

In recent years, mass timber construction has gained traction as an eco-friendly and efficient building method. This approach, lighter and faster to assemble than traditional methods, carries a climate advantage by storing carbon drawn down from the atmosphere.

Several German federal states have integrated massive timber construction into their building standards, with notable updates such as the January 2025 amendment to the Bavarian Building Code easing regulations and promoting innovative, resource-efficient building methods. Canada, too, has been embracing mass timber, with the 2020 National Building Code permitting 12 stories of encapsulated mass timber construction, and the 2025 edition moving to 18. Australia and New Zealand also permit mid-rise timber under their national codes.

Fire safety, however, remains a concern. Repair of charred timber and assessment of residual capacity after a fire is an open question. The extent of exposed timber that can be safely allowed in different occupancies is still under study.

Fortunately, fire testing has shown that mass timber elements routinely achieve 1 or 2 hour ratings and in some cases much longer, meeting or exceeding performance standards. Fire service tactics for timber buildings are being refined, and adding layers of drywall or a water mist system can reduce insurance premiums and smooth approvals.

Canada has an opportunity to lead in mass timber safety by harmonising with U.S. provisions, funding more full-scale tests, and requiring construction phase fire plans. Bringing a fire engineer in early, deciding on how much wood to expose, planning encapsulation accordingly, talking with building officials and insurers, implementing strong fire controls during construction, and having a plan for assessing and repairing any fire damage if it occurs can reduce risk and build confidence.

Design strategies for mass timber include the use of sprinklers, encapsulation with gypsum board, fire-rated detailing, and limits on exposed timber surface in larger compartments. More data on real fires and demonstration burns, better construction phase controls, and transparent engagement with insurers will eventually bring premiums for timber in line with those for steel and concrete.

In full-scale compartment burns, timber buildings have shown to remain standing through burn out without collapse. Engaging a fire engineer and the authority having jurisdiction early can prevent delays and redesigns. A national database of fire incidents and test results can reduce uncertainty faster.

The marginal investment in fire protection can pay for itself in avoided financing costs and faster project delivery. Connection performance, especially in innovative seismic designs, requires more fire testing. Creating a harmonised approach to mass timber safety across nations can pave the way for a more sustainable future in construction.