Fifteen structural composite lumber (SCL) products including laminated-veneer lumber (LVL), laminated strand lumber (LSL), oriented strand lumber (OSL), and parallel strand lumber (PSL) provided by Boise Cascade, LP, West Fraser, and Weyerhaeuser were tested for moisture-related properties in this study, also covering four reference materials: 16-mm Oriented Strand Board (OSB), 19-mm Canadian Softwood Plywood (plywood), 38-mm Douglas-fir and lodgepole pine solid wood. Water absorption, vapour permeance, vapour sorption, and dimensional stability were measured with limited replication by following relevant standards for a purpose of assisting in improving building design and construction, such as hygrothermal modelling of building envelope assemblies, design for vertical differential movement, and on-site moisture management.