How to Level Your Floor From the Top Side

Use a prybar to pull baseboards and trim from the walls surrounding the floor that you need to level. Slide the tip of the prybar between the wall and the boards and then pull the boards away from the wall at any location where the boards are nailed into place.

Clear away any dirt or debris from the floor with a broom, and then mop the floor clean using a pH-neutral cleanser. Use clean water to rinse off the floor surface, and then pat the floor dry with cloth rags.

Place a level bar onto the floor against the far wall. Run the bar over the floor while watching the base of the bar to note if it’s lifted from the floor due to a rise in the floor surface, or if you can see a gap beneath the bar indicating a drop in the floor level. Mark raised areas of the floor with a piece of colored chalk, and use a different colored piece of chalk to mark low points.

Reduce high areas in the floor using a concrete grinder for concrete floors and a floor sander for wooden floors. Check the area after grinding to make certain it's level with the surrounding surface by running the level bar over the surface a second time.

Prepare concrete floors for leveling by spreading a layer of epoxy adhesive over the floor’s surface. Use a paintbrush to apply the adhesive, and then wait for the adhesive to dry enough to lose its wet look, but not enough to lose its stickiness when touched.

Level the concrete floor to fill in the low areas by spreading a liquid floor leveling compound over the floor using a squeegee. Pour the compound over the floor, beginning with the low areas, and then spread the compound to cover the entire surface with a layer 1/4-inch thick. Allow the compound to dry for 48 hours before using the floor.

Remove the boards from the depressed floor areas to level the low areas of wooden floors. Use the prybar to lift the boards from the subfloor at the point where the boards are nailed into place. If the boards are glued into place, direct the heat from a heat gun over the surface of the glued board for about 30 seconds to loosen the adhesive holding the board into place and then pry the board up. For floating hardwood floors, you’ll need to disassemble the floor leading up to the depressed section by unhooking the boards beginning at the nearest wall to the repair area. Lift the side of the board nearest the wall to unhook it from the next row of boards and then pull the unhooked board away. Continue to remove the boards until you’ve exposed the depressed floor section.

Cut pieces of 15# felt to use as shims in the depressed section of the wood floor. Cut a piece of shim that’s as large as the depressed section using a utility knife, and then cut progressively smaller sections of felt, decreasing in size about 1/2-inch in diameter for each successive piece. You’ll need as many pieces of felt as necessary to fill the depression until the top of the felt is level with the surrounding subfloor surface.

Place the smallest piece of felt shim in the center of the depression, and then layer them using the successively larger pieces until you’ve filled the floor depression. Secure the shims in place with carpet tacks placed every 5-inches throughout the top shim’s surface and descending to the subfloor beneath. Sand down the edges of the felt to taper it against the subfloor surface to remove any height differential between the felt and the subfloor.

Sweep the floor clean, and then replace the floorboards.

Replace the baseboards at the new floor height. If needed, cut the base of the door trim with a hacksaw to fit the new floor height.