Cross-laminated timber (CLT) panels are increasingly used in mid-rise or even taller structures in North America, due to their good structural and fire safety performance, carbon storage capacity, light weight, and prefabricated nature. However, prolonged exposure to moisture during construction and in-service is a durability concern (e.g., mould growth, decay) for most wood products, including CLT. To investigate practical solutions for managing construction wetting that could occur to mass timber construction, CLT specimens with a range of moisture protection measures (e.g., membranes, water repellents) in six groups, simulating various wetting and drying scenarios, were tested in the backyard of FPInnovations’ Vancouver laboratory from October 2017 to January 2018. The specimens were directly exposed to the rainy wintertime weather or a sheltered exterior environment. Wood moisture content at specific locations/depths and weight changes of each specimen were monitored during the test. As a follow-up, this study investigates the wetting and drying behaviour of CLT through 2-D hygrothermal modelling, using a well-known hygrothermal simulation program, DELPHIN, and validated by measured moisture content from the test. This modelling study aims to emphasize the importance of using appropriate material property data based on suitable test methods. Other assumptions used in modelling should also reflect wood’s unique characteristics including its anisotropic nature. Recommendations are provided at the end of this report on how to further improve hygrothermal simulations. The overarching objective of this study is to improve hygrothermal modelling tools that can be used for the design and construction of mass timber structures.
