Quantifying fire behaviour in gaps in CLT panel-to-panel connections

Abstract

Dimensional tolerances of mass timber construction typically result in small gaps between mass timber panels. The Fire Design Specification prescribes that when gaps within elements exceed 3 mm the mass timber within the gap must be treated as fully fire-exposed surfaces. Therefore, many of these gaps must be filled with fire protection material. However, the process of protecting these gaps is time consuming and costly. To evaluate the influence of gaps on fire dynamics and char propagation, the authors performed a series of experiments on cross laminated timber panel- to-panel connections to evaluate the influence of connection type and gap size. Temperatures were measured to quantify the fire behavior of the mass timber connections. Each specimen was exposed to the standard fire (ASTM Ell9) for an hour. The development of char within connection gaps was overestimated by the Fire Design Specification in almost all cases. When considering unprotected gaps, connection type and geometry had the greatest impact on fire performance.

Citation

Garrett, Wyatt; Fischer, Erica; Hasburgh, Laura. 2025. Quantifying fire behaviour in gaps in CLT panel-to-panel connections. In: World Conference on Timber Engineering. Brisbane, Australia. June 22-26, 2025. 3684-3692. https://doi.org/10.52202/080513-0451.