Sheathing
Sheathing refers to the protective outer layer of boards or panels, typically made of engineered wood like plywood or oriented strand board (OSB), that is fastened to the structural framing of a building's walls, floors, or roof. It serves as a vital structural component by tying framing members together to increase shear strength and provide a stable, uniform nailing base for exterior finishes such as siding, shingles, or masonry veneer. Beyond its structural role, sheathing acts as a secondary barrier against the elements, helping to insulate the structure and protect the interior framework from moisture and wind infiltration. Depending on the application and material used, sheathing can be classified as structural, providing rigidity and load distribution, or non-structural, primarily offering thermal insulation and weather resistance.

