OSB (Oriented Strand Board)
Affiliate link — we may earn a commissionOSB is an engineered wood panel made from compressed wood strands arranged in layers, with each layer oriented perpendicular to the one below it. This cross-layering gives it strength in both directions, similar to plywood. Standard thicknesses are 7/16-inch for wall sheathing and 3/4-inch for subfloor. OSB costs 15 to 25% less than plywood for the same thickness. The strands create a rougher surface than plywood, and OSB holds moisture longer once it gets wet. The edges swell noticeably if they stay damp. Modern versions (AdvanTech, ZIP System) have improved moisture resistance with resin-saturated strands.
Why It Matters
OSB is the default sheathing material for walls, roofs, and subfloors in new construction. It's cheaper than plywood and structurally equivalent for most framing applications. Know its limitations: the edges absorb water, and it doesn't hold a screw as well near the edge as plywood does. For exposed applications or anywhere moisture is a concern, plywood is the safer choice.