sheathing

Sheathing is a structural panel attached to the exterior faces of building framing, such as walls, floors, and roofs. It provides rigidity to the structure, forms a substrate for finishes, and contributes to the enclosure’s integrity by distributing loads and helping control moisture and air infiltration when used with appropriate barriers. Exterior sheathing is typically covered by a weather-resistive barrier and siding, while interior sheathing is less common in modern construction.

Common exterior sheathing materials include wood-based panels such as plywood and oriented strand board (OSB). Other options include fiber cement boards, gypsum-based sheathing, and insulated foam sheathing panels that add thermal resistance. The choice of material depends on climate, structural requirements, cost, and compatibility with the exterior finish.

Functions of sheathing include providing a continuous surface for attaching siding or roofing, adding shear strength to resist lateral loads, and serving as a base for moisture and air barriers. When used with a weather-resistive barrier, it helps manage moisture by directing water to the exterior and reducing air leakage. In roofing applications, deck sheathing provides a stable surface for underlayment and roofing materials.

Installation considerations center on proper fastening, edge detailing, and moisture management. Many systems employ seam sealing or taping, and some use a rainscreen approach with a ventilation gap behind the siding to promote drying. Insulating or advanced foam sheathing requires careful detailing at edges, joints, and openings to maintain energy performance and prevent moisture problems.