OSB is a structural wood sheathing panel that is primarily made up of hardwoods (aspen, birch and popular) and softwoods (lodgepole pine and southern pine) that are combined with synthetic resin, liquid wax and other additives.

The typical OSB manufacturing process begins with the harvesting of smaller diameter trees than those typically selected for dimensional lumber. OSB panels can be produced from both barked and debarked trees.  When the felled trees arrive at the manufacturing plant, the trees are fed into a waferizer that cuts the trees into strands of wood. The size and shape of these wafer strands depends on the waferizer the manufacturer uses and will have some variation in shape due to the process. The cut wafers are then dried to obtain an optimum moisture content that may vary by manufacturer (often as low as 6%). The final moisture content must compensate for the addition of the bonding resins and any other agents that the manufacturer adds to the mix.

As part of the forming process, the wafers are directed to a mat former where the wafers are laid in one direction to form the first face of the panel. Additional mats are then created by placing new wafers in opposing directions to give the panel its structural rigidity. OSB panels are typically made up of three to five mat layers. During the forming process, the resins and other additives are added to the mats. After the forming process is complete, the formed panel is hot pressed to form the panel's final thickness. During this step, the formed panel is subject to both high pressures and temperatures to activate and cure the resins. After the hot pressing and baking processes are complete, the panels are cooled, trimmed, edge-painted and then packaged for shipping.