Not many years ago, buildings 10 stories or higher made primarily of wood would have been unthinkable. Today, hundreds of these tall wooden structures are being built in the United Kingdom alone, and many more are planned around the globe, including some truly massive structures with heights in excess of 50 stories.
While architects and environmentalists tout wood’s strength, versatility, and sustainability, some fire safety officials worry how these structures withstand fire.
“We are building combustible structures to greater heights, and anytime we go to greater heights it introduces more challenges for the fire service,” said Sean DeCrane, a 26-year veteran of the Cleveland Fire Department, and now the manager of industry relations for building life safety, security, and technologies at UL. DeCrane spoke at the 2018 NFPA Conference & Expo in Las Vegas last June during an education session titled, “Regulating Timber in Tall Buildings,” a panel discussion involving engineers, wood industry representatives, researchers, and others.
Watch NFPA's interview with Sean DeCrane
While several of his co-presenters were very bullish on the virtues and future of tall wood buildings and mostly downplayed any fire and safety concern, DeCrane’s view was cautiously optimistic.
“We know there is growing interest (in these structures), and this requires growing research,” he said in an interview with NFPA after the presentation. “We are building that knowledge base, and I think we are headed in the right direction.”
DeCrane, an NFPA member, has played a role in the research now being done to better understand how these tall wooden structures burn. This year, the Fire Protection Research Foundation released a report, “Fire Safety Challenges of Tall Wooden Buildings,” consisting of six, full-scale burns to assess how exposed timber might impact fire growth in a compartment or room made of 175-mm thick five-ply cross-laminated timber panels (CLT) panels. CLT, perhaps the most popular material used in mass timber construction, generally consists of three to seven layers of timber boards crisscrossed and bonded together with glue for maximum strength. DeCrane, who sat on the technical panel of advisors for the project, said that the study revealed how “critically important it is to ensure consistency of product and installation,” noting that the fire conditions changed dramatically during one test when the workers missed sealing a top wall joint.
After burning six simulated apartment rooms made of CLT panels—each 30 feet long, 15 feet wide, and nine feet tall, and filled with modern furnishings—researchers concluded that the exposed timber did influence the way the fire behaved. “In all tests with exposed CLT surface(s), flashover occurred approximately three to five minutes earlier than the two baseline tests (i.e., ≈ 15 min),” the report concludes
More work like this is critical “to ensure the performance of these buildings under fire conditions, and that the systems designed into these structure will perform well when under duress,” DeCrane said. “From the fire service perspective, we still have some questions and some consistency issues we’d like to see addressed, but we going down that road and I am confident we are doing our due diligence,” he said.