How to Level a Floor for Tile in 7 Steps

Using a straight edge that’s at least four feet long, place the tool on the floor. As the name implies, the straight edge should sit straight along the floor, but if you notice any gaps, that identifies a low spot. If the tool is raised in some areas, that is evidence of a high spot. 

Use chalk, a pencil, or another writing tool to mark any low points and high points. Repeat with the straight edge until you’ve checked the entire room.

Once you’ve noted where the low points are in the floor, use a measuring tape to note how deep these divots go. Jot down the measurements. This information will help you determine how much material you need to properly fill the low points.

If you’re working with wood subfloors, use caulk to seal any gaps, cover nails, and fill the seams between wood planks. This will help create the smoothest surface possible after you apply a self-leveling compound to the subfloors.

You can find self-leveling compound at a home improvement store, and this material will be your best friend in leveling a floor for tile installation. Suit up in your protective gear, then mix the self-leveling compound in a bucket according to the product instructions. Pour the resulting mixture in the low areas, spreading it out with a trowel. Follow the dry time listed in the instructions.

Head to the areas you marked as high spots while donning your protective gear, including gloves, a mask, goggles, and work boots. For wood subfloors, use a belt sander to sand down the high points. For concrete subfloors, you’ll need to rent a cement grinder to smooth out the peaks.

Revisit the areas you filled with self-leveling compound once the compound is fully dry. If there is too much compound in some areas, use the sander or grinder to smooth out these areas. Make sure to clean up the area with a wet-dry vacuum afterward to ensure the flooring is as clean and level as possible.

For wood subfloors, you can further ensure the most level surface possible by installing backer board. Using a backer board scoring tool, cut the backer board to the correct size to fit the space. Then, you’ll apply a thinset mortar to the subfloor with a trowel, creating notches with the notched end of the trowel for better adhesion. Lay each piece of backer board onto the mortar.

To finish installing the backer board, use a drill to screw the perimeter of the backer board into the wood subfloors. Place a screw about every eight inches, or follow the guided markings on the backer board. Stagger the boards, so the end of one board isn’t aligned with the edge of another board.

Use fiberglass tape to cover the backer board joints, then use the trowel to cover the tape with thinset mortar. If you choose to install backer board, it needs an extra one to two days for the thinset mortar to fully dry before you can begin tiling.

Once the floors are thoroughly leveled, make sure to pass through the room with a wet-dry vacuum to clean up any debris that kicked up while you worked. Once the materials are fully dry and the room is clean, you can begin the tile installation process.