How to Lay New Tile Over Old

A tile floor requires a strong, immobile underlayerment like cement board or concrete. An existing tile floor can be as good an underlayment as any, provided it's solid and unbroken, and that the surface is flat and not mounded or sculpted as some types of tile are. A highly glazed existing tile will be more difficult to work with than a dull form (new mortar will have a harder time adhering to glazed tile). In any case, extreme chemical cleaning of the existing tile first is crucial.

Things You'll Need

• Rubber gloves
• Trisodium phosphate (TSP) powder
• Bucket
• Stiff scrub brush
• Mop
• Chalk snap line
• Thinset mortar
• Notched trowel
• Tile cutter
• Grout
• Grout float
• Sponge

Instructions

1. Put on rubber gloves. In a bucket, mix a solution of 1 gallon warm water to 1 cup TSP powder. Thoroughly scrub the tile floor with the solution, using a stiff scrub brush. Mop rinse, then let the floor dry completely.

2. Lay your snap line across the center of the room in one direction, then the other, making two intersecting lines that cut the room into four sections.

3. Spread thinset mortar around the intersection of the lines with your notched trowel.

4. Press your first tiles into place at the middle of the room, using the lines as guides and spacing the tiles evenly. Build out toward the walls. Cut the end tiles as necessary using your tile cutter. Let the tiles set overnight.

5. Spread grout over the tiles with your grout float, starting at one corner of the room and working your way across. Work in sections of a few square feet, pressing the grout into the spaces between the tiles, squeezing it off the tile face, letting it sit in the lines for 10 minutes, then wiping down the surface with a damp sponge to take up the residual grout. Let the grout set for two days before using the floor.

Tips & Warnings

• Always wear eye protection when cutting tiles.

References

• FloorsTransformed.com: Tile Over Tile.