Get Ready to Lay a Solid Foundation: A Guide to Installing Plywood Underlayment

Installing plywood underlayment is an important step that can make or break the end result of your flooring. A well installed underlayment will provide a smooth, solid underlayment, preventing any imperfections from showing through the flooring. Poorly installed, it can leave visible depressions, bumps and other blemishes in the finished floor, causing an unappealing look. The best results come when you use the highest quality materials, follow the instructions for installation, and take the time to do the job properly.

The first step in installing plywood underlayment is to thoroughly clean the subfloor and make any necessary repairs. Scrape away any dirt and debris, fill in any holes or cracks, and use wood filler to patch any uneven areas. Inspect the entire floor and remove any protruding nails. Next, measure the area, and purchase the necessary amount of 4×8 ft. panels of ¾-inch CDX plywood. Set the plywood out on the floor, arranging the panels to interlock wherever possible and stagger the ends.

Once the pieces are cut, lay them on their sides to allow for better acclimation to the room’s temperature and moisture levels. This will help reduce any warping when the plywood is eventually installed.

Before nailing the plywood underlayment into place, double-check that the subfloor is clean and completely dry. To ensure a flat underlayment, some builders suggest applying a thin adhesive before laying the panels. Unless applied uniformly, however, the adhesive could cause the plywood to be uneven when affixed.

Starting at one end of the room, lay the panels flat and nail them into the subfloor using 1.5-inch ring-shank nails. Place them 4 inches apart along the edges, and 6 inches apart across the rest of the panel. Aim for a random pattern, so the nails won’t show through whatever sort of flooring is installed. Be sure to wear safety glasses when nailing, and fill any rough spots with wood filler once finished.

Your underlayment is now ready for installation. Depending on the type of flooring you plan to install, additional steps may be needed. Using a felt pad for hardwood floors is recommended, and for laminate, a cushioning pad is usually necessary.

By taking the time to prepare and properly install plywood underlayment, your floors can look professionally finished and add to the beauty of your room.