Fire Behaviour of Gaps in Cross Laminated Timber Panel-to-Panel Connections
| Authors: | Wyatt J. Garrett, Erica C. Fischer, Laura Hasburgh |
| Year: | 2026 |
| Type: | Scientific Journal |
| Station: | Forest Products Laboratory |
| DOI: | https://doi.org/10.1007/s10694-026-01999-9 |
| Source: | Fire Technology |
Abstract
Mass timber construction results in small gaps at abutting members due to construction tolerances and varying moisture conditions, among other reasons. These intersections, typically at connections, may have detrimental impacts on the fire performance of a structure causing loss of fire integrity earlier in the fire and thereby enabling the spread of fire. However, there has been a lack of testing to explore the effects of these gaps on the fire behaviour of mass timber, particularly at cross laminated timber (CLT) panel-to-panel connections. To investigate the fire behaviour of CLT with gaps at the panel-to-panel connections, twenty-five unprotected, unloaded CLT panels with gaps (3 and 6 mm) were tested. Panels were exposed to the standard fire (ASTM E119) for one hour. Temperature and char depths were measured to explore the influence of connection geometry and gap size. The results were compared to current design guidance provided in the Fire Design Specification (FDS) for Wood Construction. The results of the analysis demonstrated that the horizontal and vertical charring between abutting members in the panel-to-panel connections was overestimated by the FDS in every specimen tested. During the cooling phase, char continued to develop in the connection gaps when unrestricted airflow was enabled. Connection geometry, gap size, and the restriction of airflow had the greatest impact on temperature rise and char development within the connection gap.