Abstract: A preservative-treated I-joist is produced by providing a web member and first and second flange members made of lignocellulosic material. Prior to assembly of the I-joist, a waterborne preservative is applied to the web and flange members, and thereafter the web and flange members are sized. The web and flange members may have a tongue-and-groove configuration for connecting the flange members to the web member. Sizing the web and flange members may include cutting one or more stocks of lignocellulosic material to produce the web and flange members, cutting grooves in the flange members, and trimming edge regions of the web member to form tongue portions to fit in the grooves. After the web and flange members are sized, the flange members are adhered to the web member to secure the web member and the flange members together.