Do You Need an Underlay for Wood Flooring on a Plywood Subfloor?

Types of Wood Flooring

• Hardwood flooring is available in either solid wood or engineered wood options. Solid wood flooring boards are solid thicknesses of wood, recommended for glued-down or nailed-down installations. Engineered wood is made of multiple plies of wood veneers laminated together. These floors are often installed as floating floors. When installing wood floors over a plywood subfloor, the flooring is typically run perpendicular to the flooring joists to provide more strength to the floor. It is possible to run the boards parallel to the joists if the subfloor is at least three-quarters of an inch thick and the joists are 16 inches apart or less.

Solid Wood Flooring

• Underlayment is not essential for the installation of solid hardwood flooring over a plywood subfloor, unless the floor is over a crawl space where moisture may be a problem. However, underlayment covers imperfections in the subfloor, provides a smooth surface for the flooring and reduces the transmission of sound between floors.

Engineered Wood Floors

• Engineered wood floors are installed with a floating floor method, meaning they are not nailed or stapled to the subfloor. All floating floors need to have underlayment installed under the floor for noise reduction, for cushioning and to provide a smooth surface for installation. Foam products, either with or without the addition of a vapor barrier, are options for floating floors.

Underlayment Options

• Underlayment of 15-pound builder’s felt vapor barrier protects a wood floor from moisture damage if that is a concern. Asphalt felt paper, asphalt laminated paper and craft paper are other underlayment options that are stapled to the plywood subfloor. For sound reduction between rooms or floors, a high-quality foam, rubber or fiber product insulates the area. Cork is another underlayment option that reduces sound transmission, cushions the floor and is used to increase the height of the floor.