A subfloor is a layer of material installed directly over the structural floor joists in a building. It serves as the foundation and support for the final flooring material, such as hardwood, carpet, tile, or vinyl.
The subfloor provides a flat, level surface and helps distribute the weight of foot traffic and furniture evenly across the floor, ensuring stability and preventing the final flooring from flexing or sagging. It also acts as a barrier, protecting the underlying structure from moisture and providing a base for additional flooring layers or underlayment.
Plywood is among the most common materials used for subfloors, particularly in North America. Read on to learn more about plywood subfloors, their relative strengths and weaknesses, and things you should keep in mind when installing floors over them.