How to Lay Vinyl Over a Sagging Wood Floor

Inspection of the Sagging Area

• The first step is to determine whether or not the sagging area is a result of poor structural integrity or just a natural depression in the plywood subflooring. A visual inspection, along with poking and prodding with a screwdriver and tapping with a hammer, determines if the sagging is from water damage or rot, requiring replacement of the subfloor. Look for soft spots. Any areas that appear to be sound and ready for installation must be filled in with a self-leveling compound to make the installation surface flat.

Self-Leveling Compound

• Self-leveling compounds are cement-based products that fill in low spots and bring them to the same level as the rest of the floor. To use them, completely clean the sagging area of the floor with a broom and vacuum. Then apply a primer coat with a paintbrush or paint roller, using a primer approved by the leveling compound manufacturer. After the primer dries, mix up the self-leveling compound according to the manufacturer instructions, pour it into the low spot, flatten it with a metal trowel and let it dry for at least 24 hours.

Fixing Structural Issues

• Structural issues cannot be covered with a self-leveling compound. Instead, they must be repaired to ensure that the floor is stable enough to provide a base for the vinyl installation. Rotting sections of plywood must be cut out and replaced with new plywood. If there is damage to the joists on the floor below, the joists must be replaced as well. If the joists appear to be in good working condition but are sagging in the middle or have too much side-to-side deflection, add horizontal bracing between the joists. Braces are joist material cut down to fit perpendicularly in between the joists and then nailed or screwed into place. Another alternative is to double up on the floor joists. This is where you install a sister joist directly alongside the existing joists.

Installation

• After the floor has been prepped and is ready for installation, it’s time for layout. When working with vinyl sheets, simply roll out a sheet and cut it to fit with a utility knife. More than one sheet may be necessary to span a room, and you should line up any patterns accordingly from sheet to sheet. Afterward, roll the sheet or sheets back up and ensure the surface is completely free of debris. Clean it with a broom and vacuum, then coat the surface with a manufacturer-approved primer to give the vinyl glue a proper bonding surface. Spread the glue onto the surface and unroll your vinyl sheet into the glue. Use a floor roller to flatten the sheeting. With vinyl tiles, first lay out the floor with a tape measure, framing square and pencil to give yourself a grid pattern to follow. Then prime the floor and apply glue with a trowel grid by grid and install your tile pieces. Peel-and-stick vinyl tiles follow the same grid and priming procedure. Always use a floor roller to ensure a strong bond.