Things You'll Need
36” wide roll of roofers felt
Hardwood floors add style and a distinct look to a room. In order to properly install hardwood floors, the plywood subflooring must be even, or level. Sanding the subfloor can remove minor swells or high spots in the wood, but any low spots in the floor must be filled in order to level the plywood. You can level the plywood floor yourself using roofers felt, a type of black paper comprised of fiberglass or polyester fleece, which will help prepare the surface for your hardwood installation.
Inspect the plywood subflooring for dips, or low spots. Use a carpenter's level to help determine the ends of each area where the subfloor sinks down. Measure the width and length of each low spot with a tape measure.
Unfurl a roll of roofing felt. Measure the felt to match the measurements of the low spots in the subfloor. Cut the felt to size with a utility knife.
Position the cut felt pieces on top of the low spots to fill them. You may need to overlap many felt pieces to fill the space. Fill the low space compactly with the felt. Any gaps or hollow spots in the felt can cause hardwood floor boards to sink slightly, resulting in creaking noises when walked on.
Install a layer of ¼ inch plywood subflooring over the filled flooring. Drill the plywood down at the corners with two-inch screws to secure it temporarily. Check the subfloor with your carpenter's level to ensure it is level.
Secure the subfloor with two-inch screws drilled through the plywood and the floor joists. Space out the screws every eight inches.
Use the first cut out piece of roofers felt as a template when cutting out additional pieces to fill one low spot on your plywood floor.
Always wear safety gloves when working with hand tools and power tools to avoid injury.