A subfloor is the layer of flooring that sits directly on top of the structural floor joists and provides a stable base for the finished floor. It is typically made from materials like plywood or oriented strand board (OSB) and helps distribute weight evenly across the floor. The subfloor also acts as a barrier against moisture and can improve insulation. Installing a subfloor is an essential step in building or renovating a home. It ensures that the finished flooring, such as hardwood, carpet, or tile, has a solid foundation. Proper installation of the subfloor can prevent issues like squeaking or warping in the final floor surface.