As with any new construction technique, mass timber presents new challenges and questions about design, construction, and maintenance best practices. Mass timber has a greater capacity to absorb and conceal moisture and a reduced ability to dry; therefore, moisture entrapment in the timber can pose significant risks to the structural integrity and long-term performance of roof assemblies. Mass timber roof systems are more sensitive to moisture exposure than roofs with concrete, steel, light wood framing, and even heavy timber decking structures.
This paper synthesizes current research, industry guidelines, case studies, and the authors’ experiences regarding moisture mitigation strategies for mass timber roofs. It also highlights areas where further research and standardization are needed to improve long-term resilience. The authors explore several moisture mitigation strategies that have proven successful, including using temporary moisture protection membranes during construction, designing assemblies with sloped structures that support drainage and drying, specifying durable membranes, and maintaining roofs proactively.