Sheathing consists of board or panel materials that are used in assembling floors, walls, and roofs. The boards may provide structural support to the structure and form a surface that other materials (i.e. shingles, siding, or flooring) can be applied to.
There are several types of sheathing, with each having a specific function based on its application, however, still the basic function of sheathing is to create a surface on which other materials can be placed to increase the stability of the building while providing increased insulation and protection. Contractors can also use sheathing to stop potential leaks, add strength to the structure, and for fireproofing.
The concept of sheathing was originally introduced in construction as an improvision in the roofing system after 1970. Prior to this, buildings were constructed with a layer of boards beneath the shingles. The space between these layers were often the cause of water damage from leaks.