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Oriented strand board

Oriented strand board, or OSB, is an engineered wood product formed by layering strands (flakes) of wood in specific orientations. In apperance it is has a rough and varigated surface with the individual strips (around 2.5 by 15 cm each) lying unevenly across each other in the direction of their grain.

It is manufactured in wide mats from cross-orientated layers of thin, rectangular wooden strips compressed and bonded together with wax and resin adhesives (95% wood, 5% wax and resin). The strips are created by shreding the wood into the strips, these are sifted and then orientated on a belt. The mat is made in a forming bed, the layers are built up with the external layers alined in the panel direction and internal layers randomly positioned. The number of layers placed is set by the required thickness of the finished panel, typically around a 15 cm layer will produce a 15 mm panel thickness. The mat is then placed in a thermal press. Individual panels are then cut from the mats in standard sizes.

Different qualities in terms of thickness, panel size, strength, and rigidity, can be given to the OSB by changes in the manufacturing process. OSB panels have no internal gaps or voids, and are water-resistant (though they do require additional membranes to achieve impermeability to water). The finished product has similar properties to plywood, but is uniform and cheaper, there is an expectation it will replace plywood in many roles. It is commonly used as sheathing in walls, floors, and roofs, as well as a variety of other applications.

OSB is relatively environmentally friendly. The production method is very efficient in using almost all the wood of the harvested trees and both small, young trees and lower quality fast growing species can be used. In 2001 19.4 million m of OSB panel was produced in the USA