Fire Testing for Efficient Tall Buildings
Research Team:
Erica Fischer
Laura Hasbargh
David Barber
Kara Yedinak
Amara Holder
Project Duration:
2020-2026
2020-2026
Facilities:
National Fire Research Laboratory at the Bureau of Alcohol, Tobacco, Firearms, and Explosives
Project Goal Statement
This project aimed to provide technical data addressing known gaps in previous CLT compartment fire testing. In particular, the researchers designed tests using high fuel loads that included modern household items (furniture, cleaning supplies, electronics). They varied the amount of fire protection on the mass timber and monitored fire behavior, temperatures within the mass timber members, and emissions throughout all phases of the tests.
Introduction/Background
Fire behavior in CLT buildings has been an increasingly active area of research as mass timber buildings gain acceptance and popularity. Numerous tests have been completed to address fire dynamics, but many of them utilized designs that didn’t necessarily replicate realistic fire conditions. Specifically, fuel loads were often lower than would be likely in a modern building environment or fuel was simulated with wooden cribs rather than modern fuels that contain high amounts of synthetic materials.
Research Methods
In this study, the researchers performed four large scale CLT compartment fire tests. Two of the tests included gypsum wall board covering all mass timber within the compartment, one had all exposed mass timber, and one had gypsum wall board only on the longitudinal walls. Three specimens were prepared with realistic heavy fuel loads, including furniture, while one compartment was tested with wood cribs as fuel. The researchers heavily instrumented the compartments, recording data including but not limited to heat release rate, mass loss, material and mass timber temperatures, air flow and emissions. throughout the tests.
In addition to the differences in the fuel type and the amount of fire protection within the compartment, these tests also explored two different geometries of balloon frame cross laminated timber connections as well as their behavior with and without fire protection.
Key Findings
Early findings showed that when three layers of Type X gypsum wall board fire protection was used throughout the compartments, the fuel was fully consumed and the fire protection did not fail during the experiments. This enabled the fire to enter the decay phase of the fire consuming the fuel within the compartment. In addition, the tests demonstrated that with fire protection, balloon-frame connections performed well and did not exhibit signs of damage or failure.
Additional conclusions have shown that there was a more intense fire within the compartment with fire protection only on the longitudinal walls compared to the compartment with full exposed mass timber. Additionally, nearly all of the assessed locations in the compartments underwent higher char rates than is prescribed in both the American Wood Council (AWC) Fire Design Specification (FDS) and Eurocode 5 as well as nonlinear char rates. These two conclusions suggest that the prescribed char rates developed from standard fire tests are different from char rates that might be in buildings with high fuel loads. In addition it demonstrates that as timber chars, this is not occurring at a linear rate. These conclusions demonstrate the need for future work on quantifying the fire demand in these types of compartments with high fuel loads and exposed mass timber so that the fire protection can be designed accordingly.
Connection research has demonstrated that when balloon-frame connections are exposed, the screws used to connect steel angles to the cross laminated timber wall can show plastic hinging behavior under only self weight. This conclusion demonstrates the need for future work on the embedment strength of screws throughout a fire scenario.
Future Work
The tests themselves are completed, but the researchers continue to process the collected data. They intend to perform fire modelling, analyze connection performance, assess the difference on char rates of vertical and horizontal services, and evaluate the emissions from each test.
Publications & Presentations
Coello, N., Fischer, E. C., Hasburgh, L., Barber, D., Yedinak, K., & Pitari, I. (2025). Fire behaviour of CLT floor to wall connections: Findings from the WOODWISE project. World Conference on Timber Engineering 2025, 1059–1068. https://doi.org/10.52202/080513-0130
Fischer, E., Pitari, I., Hasburgh, L., Barber, D., Yedinak, K., & Coello, N. (2025). WOODWISE: Large-scale compartment fire tests examining sustainability, smoldering, and emissions. World Conference on Timber Engineering 2025, 4252–4259. https://doi.org/10.52202/080513-0522
Hasburgh, L., Fischer, E., Barber, D., Yedinak, K., Holder, A., Coello, N., & Pitari, I. (2025). Influence of fuel type and load on fire intensity: Results from full-scale fire tests from the WOODWISE project. World Conference on Timber Engineering 2025, 5145–5153. https://doi.org/10.52202/080513-0633
Fischer, E. (2025, November 4). WOODWISE: Wood Optimization for Occupant Safety. 2025 Mass Timber Research & Design Innovation Symposium, Corvallis, OR. https://www.youtube.com/watch?v=pTMKFVvUTHA
Funding & Acknowledgements
TDI ARS
EPA
NIFA