Mold can sometimes grow on building materials that are wet or held in a humid atmosphere. Wetting can be by liquid water or water vapour or both. Of the wood-based building products, oriented strandboard (OSB) is perceived by some specifiers as being one of the most susceptible to mold growth. A potential tool to control mold growth in the event that oriented strandboard gets wet in transit, in storage, or at a sales or use location, is chemical treatment. The objective of this study was to obtain information on what surface treatments prevent mold growth when dry OSB is wetted by water vapour under conditions of high humidity.