Wood Panels Guide [PDF]
Plywood is made with plies (sheets) of wood veneers that are glued together under heat and pressure. It replaced shiplap boards as sheathing on walls and floors and spaced boards on roofs. Plywood is stronger and stiffer when the grain of the face veneers are oriented perpendicular to supports, which is the typical orientation for most floor and roof applications.
OSB was invented in the late 1970s in response to greater demand for housing and commercial buildings, a decreasing supply of older trees, and increasing environmental restrictions on logging.
OSB is made with layers of thin, rectangular strands or flakes of wood that are produced by feeding freshly cut hardwood or softwood logs through a cutting machine called a strander. Each layer of strands is alternately placed perpendicular to the previous layer, which provides bending support in two directions.
Applications in Construction
Wood-based structural-use panels are available in many thicknesses, ranging from 1/4" – 1-1/4". They are manufactured as one of several types, identified by the intended end-use. These panels are used for sheathing on roofs, subfloors and walls; underlayment in floors; single-floors (combination subfloor and underlayment); tongue and groove; siding; and structural insulated panels.
Panels used in construction must be certified under U.S. Department of Commerce standards by approved third party agencies. Manufacturers must test their panels for quality and performance on a regular basis.