OSB

OSB, or oriented strand board, is an engineered wood panel formed from rectangular wood strands that are oriented in cross-laminated layers and bonded with resin adhesives under heat and pressure. The strands are usually softwood and are laid in alternating directions to impart strength in multiple axes. The resulting panels are used as structural sheathing and as subfloors in a variety of building applications.

Manufacturing and characteristics: Wood strands are prepared, dried, and coated with resin and wax before being laid into mats with alternating orientations. The mats are pressed into panels and then cut to standard sizes. Common thicknesses range from about 9 to 25 mm (3/8 to 1 inch), with standard panel sizes around 4 by 8 feet (about 1.2 by 2.4 meters). OSB is produced in several grades, commonly designated OSB-1 through OSB-4 in European and North American standards, where OSB-3 and OSB-4 are moisture- and load-rated for exterior and more demanding conditions.

Uses and performance: OSB is widely used for structural sheathing in walls and roofs, as well as subflooring and underlayment. It offers good stiffness and dimensional stability at a lower cost than many alternatives. Moisture resistance varies by grade and adhesive type; exterior or moisture-exposed applications typically require higher-grade OSB (such as OSB-3 or OSB-4) and protective weather barriers.

Environmental and standards: OSB is typically made from fast-growing wood species and can maximize wood fiber yield. Adhesives may include phenol-formaldehyde or low-formaldehyde formulations. Standards and ratings are provided by regional organizations (such as EN 300 in Europe or APA ratings in North America) to specify mechanical properties and moisture performance.