How to Install Ceramic Tile Over Concrete Floor With Cracks

As intricate as you'd like

Ceramic floor tiles should always be installed over a hard, immobile and unbroken surface. A concrete floor is a terrific underlayment for ceramic, but it's important that it be properly prepared. Cracks in the concrete can make the surface uneven, causing the tiles not to set properly, and those cracks might also admit moisture that could loosen the tiles over time. Concrete leveler is a very thin paste that will fill in those cracks and help get the concrete ready for tiling.

Things You'll Need

• Portland-cement-based floor leveler (liquid)
• Long cement trowel
• Trisodium phosphate cleaner
• Bucket
• Scrub brush
• Chalk snapline
• Square
• Thinset tiling mortar
• Tiling trowel (with notches)
• Floor tiles
• Tile spacers
• Tile cutter
• Grout
• Grout float (flat rubber trowel)
• Sponge

Instructions

1. Make sure there is no loose or crumbling concrete anywhere on the floor, including inside the cracks. Pour concrete leveler over each crack, filling it completely and letting it come up over the sides. Smooth out the leveler with a cement trowel, getting it flat and level against the concrete. Continue until all the cracks are filled and the floor is completely flat, smooth and unbroken.

2. Let the leveler set for a day. Scrub the floor thoroughly with a solution of 1 cup trisodium phosphate to 1 gallon of warm water. Rinse well. Let it dry for two to three days.

3. Stretch the chalk snapline over the center of the concrete floor, between two of the walls at the middle, and snap the line. Stretch the snapline across the middle of the floor in the perpendicular direction, so it intersects the first line at the middle. Before you snap it, set a square at the intersection and adjust the string as necessary to get it completely square.

4. Use your tiling trowel to lay a few square feet of thinset tiling mortar over the intersection. Set your first floor tiles in place at the intersection, using the lines as guides and putting spacers between them.

5. Build out toward the walls, laying down more mortar and setting the rest of your tiles, with spacers between them. Cut the tiles on your tile cutter to fit by the wall, as needed.

6. Let the tiles set for 24 hours. Remove the spacers.

7. Spread grout over the floor with your grout float, forcing the grout into the spaces between the tiles and scraping it off the surface. Use a damp sponge to remove the excess grout. Let the grout set for a few day before using the floor.

Tips & Warnings

• Wear eye protection while cutting your tiles.

References

• Floors Transformed: Tiling Over a Concrete Slab