Subflooring is the layer of material installed directly on top of the floor joists in a building. It serves as a foundation for the finished flooring, providing stability and support. Common materials used for subflooring include plywood and oriented strand board (OSB), which help to distribute weight evenly and reduce noise. In addition to structural support, subflooring can also help with insulation and moisture control. Proper installation of subflooring is essential for the longevity of the finished floor, as it can prevent issues like warping or squeaking. Overall, subflooring plays a crucial role in the flooring system of a building.