Fire behavior of CLT floor to wall connections: Findings from the Woodwise Project

Abstract

Cross-laminated timber (CLT) is increasingly used in multi-story construction due to its structural efficiency and sustainability. However, the fire performance of CLT floor-to-wall connections remains a critical concern, particularly in balloon-frame construction, where there are complex interactions between the steel and timber components and fire-induced degradation of both materials can compromise structural integrity. This study, part of the WOODWISE project, examines the fire behaviour of CLT floor-to-wall connections through large-scale compartment fire tests. The research evaluates the effects of connection configuration and encapsulation on char depth and charred area. Two connection types-exposed and concealed steel angle connections-were tested under fully exposed and fully encapsulated conditions. Results indicate that concealed steel angle connections exhibit greater char depth than exposed steel configuration. Comparison of measured char depths with prescriptive design standards indicated that actual charring can exceed values predicted by code standards, particularly in concealed steel angle connections and under more severe fire exposure scenarios. Encapsulation significantly reduces char propagation, highlighting its effectiveness in improving fire resistance. Additionally, compartment encapsulation influences fire dynamics, affecting heat exposure and char development. These findings contribute to the importance of connection detailing in exposed timber structures.

Citation

Coello; Nicolas; Fischer, Erica C.; Hasburgh, Laura; Barber, David; Yedinak, Kara; Pitari, Ines. 2025. Fire behavior of CLT floor to wall connections: Findings from the Woodwise Project. In: World Conference on Timber Engineering. Brisbane, Australia. June 22-26, 2025. 1059-1068. https://doi.org/10.52202/080513-0130.