Basic Carpentry Name: Morning/Afternoon

Structural Sheathing Aim: What is the function of sheathing and how is it installed?

Sheathing is the board or panel material used in floor, wall and roof assemblies of both residential and commercial construction. Exterior wall sheathing strengthens the wall system, provides a nailing base for the siding, and gives a layer of protection against outside elements. Exterior wall sheathing is often structural. Structural exterior wall sheathing ties framing studs together, making the walls resistant to twisting and bending. However, most structural exterior wall sheathings lack insulation value. There are several types of sheathing, each having a specific function based on its application. Sheathing though, whether on exterior walls, floors, or a roof, are a structural component of a house or building, meaning that they are required for the building to remain standing and withstand forces such as extreme weather.

Structural sheathing is attached to the exterior wall framing, bracing the walls against positive and negative forces (weather). There are several different types of structural sheathing to choose from; they can be either wood (plywood), sheetrock or cement based sheathing. Wood based structural sheathing includes plywood, oriented strand board and waferboard. Roof sheathing is also structural, providing bracing of roof framing members (such as roof rafters), and it carries weight from above to the rafters and trusses below. Similar to exterior wall wood sheathing, roof sheathing also includes plywood, oriented strand board and waferboard.

When sheathing a house or building, whether it is a floor, wall or roof, the seams must be staggered in order to maintain its structural rigidity. When staggering seams, make sure that the end of the plywood does not fall in line with another sheet of plywood above or below it. As seen in the picture below, the two pieces of plywood at the bottom are centered on the piece above it. This ensures that all the weight of the structure is better distributed, giving a more structurally sound home or building.

Example of staggered seams being installed on a roof. Whether on a subfloor, wall, or roof, seams must always be staggered.

Answer the following questions in 3-5 complete sentences. 1. In your own words, define the term structural. Is sheathing a structural component of a house or building? Explain your answer.

2. Why do the plywood seams of sheathing need to be staggered?