A subfloor is the structural layer of flooring that sits directly on top of the floor joists. It provides a stable base for the finished flooring material, such as hardwood, tile, or carpet. Typically made from materials like plywood or oriented strand board (OSB), the subfloor helps distribute weight and adds strength to the overall flooring system. In addition to structural support, the subfloor also plays a role in insulation and soundproofing. Proper installation of the subfloor is crucial, as it can affect the durability and performance of the finished flooring. Regular maintenance can help prevent issues like moisture damage or squeaking.