subflooring

Subflooring is the structural layer of a floor that sits on top of the floor joists and provides a flat, stable surface for finished flooring. It carries load, resists flexing, and works with underlayment and finishes to form the completed floor assembly. The subfloor must be dry, level, and securely fastened to the joists to prevent movement and squeaks.

In most wood-framed buildings, subfloors are made from panels such as plywood or oriented strand board (OSB). Concrete slabs can act as a subfloor, often with a separate underlayment or a cement board when tile or laminate is installed. Some applications use gypsum-based or cementitious underlayments over the structural base to provide a smooth, finished surface for specific floor coverings.

Key installation considerations include ensuring flatness and compatibility with the finished floor. Panels should be properly aligned, edges supported, and fastened according to the manufacturer's guidelines and local codes. Joints and seams should be staggered, and edges must be supported along the full length of the joists. Moisture control is essential; wood subfloors require acclimation to room moisture, and vapor barriers or moisture barriers may be used with concrete slabs. For radiant heating or tile, specific subfloor types such as cement board may be required.

Maintenance and repair involve replacing damaged panels and addressing moisture-related issues promptly. Warped, soft, or moldy areas indicate moisture problems or rot and should be investigated. Squeaks often result from loose fasteners or warped joists and may be remedied by fastening, sistering joists, or underlayment reinforcement.

Subflooring serves as the foundation for most finished floors, including carpet, hardwood, laminate, vinyl, and tile. The choice of subfloor material and thickness depends on the structural design, anticipated loads, and the chosen finish, making proper installation and moisture management important for long-term performance.