To level a floor, measure the gap between the leveled and unleveled surfaces, and then cut triangular leveling strips to fill the gap. You need a long level, a saw, 2-inch by 10-inch boards, a power drill with a drill bit, screws, construction adhesive, a framing nailer and nails.
- Remove the subfloor
If you are leveling an existing floor, remove all carpeting, tiles and wood flooring that's covering the subfloor before removing the subfloor altogether.
- Measure the distance of the gap
Place a long level on an unleveled area of the floor. Raise the level until the bubble is centered, and then measure the distance from the unleveled surface to where the level is balanced.
- Cut a leveling strip using the measurement
Use the measurement to cut a leveling strip out of a 2-inch by 10-inch board. The strip should form a triangle with a long, downward slope where the distance between the top of the slope and the bottom of the triangle matches the measurement.
- Attach the strip
Position the strip slope side down against the unleveled surface. Drill holes into the strip that are 16 inches apart, and then use the drill to install screws into each hole.
- Attach more strips
Measure, cut and attach more strips until the entire base of the floor is leveled enough to install a subfloor.
- Apply construction adhesive to each strip
Apply a layer of construction adhesive to the top of each strip.
- Install the subfloor
Lay 3/4-inch plywood atop the strips, and secure the subfloor into place with a framing nailer.