Summary
Mass timber construction is gaining popularity due to its sustainability, aesthetic appeal, and construction efficiency. However, drying cracks in mass timber elements such as cross-laminated timber (CLT) and glue-laminated timber (glulam) pose challenges both in terms of appearance and structural integrity. These cracks form when moisture-induced stresses exceed the tensile strength of the wood, particularly when exposed to sudden environmental changes. This paper presents a conceptual approach to developing guidelines for managing indoor temperature and humidity conditions to minimize drying cracks after construction.The authors outline five key scenarios that contribute to moisture-related stress in mass timber, with a focus on rapid drying caused by construction exposure and abrupt shifts in indoor climate once HVAC systems are activated. While some industry guidance exists, there is a lack of specific recommendations on temperature and humidity settings to mitigate cracking risks. The paper proposes using hygrothermal simulations combined with laboratory measurements to assess moisture gradients and their impact on wood behavior. By identifying critical moisture thresholds, practical guidance can be developed to help prevent cracking and ensure mass timber remains structurally sound and visually appealing.To support this effort, the study examines moisture gradients in glulam beams under different initial moisture contents and relative humidity levels. Simulations show that higher moisture differentials create more stress, increasing the likelihood of cracking. The research suggests that a gradual reduction in humidity is key to limiting these stresses. Ultimately, the study calls for further field validation and the establishment of standardized commissioning protocols that balance construction drying rates with indoor environmental conditions.
