NFPA Journal

This spring, before the world came to a standstill due to COVID-19, I attended a workshop on fire safety of tall wood buildings, arranged by the Fire Protection Research Foundation. The purpose was to review the research and design approaches available to address fire safety in these buildings and to identify and prioritize future research needs. Over two days in Portland, Oregon, researchers from the US, Canada, the UK, Sweden, and Australia presented their findings, and designers presented case studies of buildings either already built or in the design phase. Participants included the wood industry, fire protection professionals, the fire service, and code enforcers. The proceedings are available at nfpa.org/foundation.

Wood is one of our oldest construction materials and is still used extensively in low- to medium-rise residential buildings. But its use in taller structures is limited by stricter fire requirements. The last decade, though, has seen a steady global push toward sustainable buildings, creating increased interest in the use of wood for tall buildings. (Though not well defined, a building can be considered tall in code context if it exceeds six stories.) According to thinkwood.com, 44 tall wood buildings are underway or have been built around the world in the past six years. The challenge is not only that the load-bearing structure of these buildings is made of wood, but that designers want the wood exposed so its beauty can be enjoyed by the occupants. While I was impressed by the work already done by the research community, the workshop also made it clear that researchers are still trying to catch up to the needs of designers.

One of the most pressing areas for additional research is the fire performance of connections between timber elements. Failure in a connection can significantly impact the load-bearing capacity of a structure and lead to premature collapse. During a fire, timber elements will char and experience a gradual loss of strength, if designed with sufficient redundancy. Most connections are made from steel, however, which can fail more rapidly when exposed to high temperatures.

Another priority for research is fire behavior in large open spaces with exposed timber. Most of our understanding of fire dynamics and the derived design methods are based on small compartment fires. Only within the last few years have the fire dynamics of large open compartments been investigated, but the impact of exposed wood on these spaces is not yet well understood.

Finally, the workshop also highlighted knowledge gaps that need to be addressed by enforcers and designers, including the challenge of ensuring that the features needed to secure the designed fire performance—such as fire protection boards, fire stopping, and suppression systems—are installed exactly as intended during the construction phase. Installers and inspectors need to understand the impact that even minor imperfections can have on the overall fire performance.

It is fortunate that fire safety has helped drive much of the research that has accompanied the global push for tall wood buildings. In stark contrast is the approach that was taken when combustible exterior walls began to be used on tall buildings; instead of responsibly acknowledging the fire hazard, the fire performance of the materials used in these applications was downplayed or even ignored, leading to the extensive use of inferior or dangerous products that have produced disasters. We should never ignore fire hazards in the pursuit of other goals. As the work on tall wood buildings has already shown, the research community is ready to take on new challenges and to help all of us understand the hazards presented by new materials and processes. I hope these efforts will help us avoid a fire disaster in a tall wood building. 

Birgitte Messerschmidt is the director of applied research at NFPA. Illustration: Michael Hoeweler