What is sheathing?

Sheathing is a structural component in building construction, typically a large, flat panel material used to cover the exterior walls or roof of a building's framing. Its primary functions include:

• Structural Support: Sheathing provides stability to the wall or roof framing, resisting racking (lateral forces from wind or earthquakes). It helps to create a strong, rigid surface to which siding, roofing, or other exterior finishes can be attached.

• Load Distribution: It distributes the weight of the exterior cladding and other loads across the underlying framing members (studs, rafters, trusses).

• Substrate for Finishing Materials: Sheathing provides a smooth, continuous surface for the installation of exterior finishes like siding, roofing, and underlayment.

• Weather Protection (to a degree): While not a primary waterproofing layer, sheathing offers some protection from the elements until the final exterior cladding is installed.

Common Sheathing Materials:

• Oriented Strand Board (OSB): A widely used engineered wood product made from wood strands bonded together with resin. It's relatively inexpensive, strong, and readily available.

• Plywood: Another engineered wood product made from thin layers of wood veneer glued together. Offers good strength and stability. Various grades exist, with higher grades being more suitable for exterior applications.

• Cement Board (Hardie Board): A fiber cement composite that is very durable, resistant to moisture, fire, and insects. More expensive than OSB or plywood.

• Metal Sheathing: Less common for residential construction, but used in commercial and industrial buildings. Offers excellent durability and resistance to fire and pests.

Sheathing Considerations:

• Grade: Different grades of sheathing exist, based on strength and moisture resistance. Exterior sheathing should be specifically designed for that purpose.

• Thickness: The thickness of sheathing impacts its strength and stiffness. Thicker sheathing is generally stronger and better able to resist racking. Building codes specify minimum thicknesses based on factors like wind load and snow load.

• Installation: Proper installation is crucial for its effectiveness. Sheathing panels should be installed correctly, with proper spacing between panels and overlapping edges. Fasteners should be adequately spaced and driven properly to prevent damage.

• Climate: The choice of sheathing material can be influenced by the climate. In humid climates, moisture-resistant sheathing is preferred.

In summary, sheathing is a vital component of building construction, playing a significant role in structural integrity and providing a base for exterior finishes. Choosing the right type of sheathing depends on factors such as budget, climate, and building code requirements.