An OSB floor is a layer of a flooring system that's known as subfloor. Subfloor is the structure that lies beneath the visible floor, which could be hardwood, vinyl, carpet, or another material. OSB, or oriented strand board, is an engineered structural panel made from compressed strands of wood arranged in perpendicular layers. OSB is different from other types of wood panels because its pieces of wood are "oriented," and placed deliberately, not at random. An OSB floor is an environmentally friendly flooring platform valued for its uniformity, strength, and versatility.
An OSB floor is made from sustainably harvested wood that comes from quick-growing trees like southern yellow pine, aspen poplar, and even bamboo. Logs are cut into strands, dried, and treated with wax and a waterproof binder. These strands are then grouped into large sheets and are subjected to high temperature pressurization. Manufacturing equipment ensures that strands are strategically oriented to overlap and interlock at a 90 degree angle. Then each strand is coated with high performance lamination glue like phenolic resin, creating a durable, rigid panel that's excellent for subflooring.
While subflooring can be made from many different materials, wood subfloors are usually used in areas where basements are common. OSB floor panels normally have tongue-and-groove edges that interlock, and are attached directly to the joists that support the floor, either by screwing or gluing, to help eliminate squeaking. The tongue-and-groove edges can also be glued together.
An OSB floor panel can be installed in a single-layer subfloor with an underlay or as a subfloor to be covered by underlayment, which provides a smoother substrate and stiffens the subfloor. The underlayment can also be made from OSB, and always goes on top of the subfloor. After the subfloor has been properly prepared, the visible floor can be installed.
An OSB floor has several advantages over other kinds of wood subflooring, particularly plywood. First, it is made from sustainably harvested lumber and therefore reduces the demand for old growth timber. It generally takes on a squarer shape and has greater shear strength with no "soft spots." It can be crafted into panels far larger than plywood, and OSB is usually less expensive, because supply tends to be nearly double than that of plywood. The biggest disadvantage of an OSB floor is that when it gets wet, the edges may expand by up to 15%, which can then affect the flooring materials that lay on top.