If you don't have room for another layer of tile over an old tile floor, you’ll have to scrap off the old tile. It's a tough job, but the right tools will make it go faster.
Work the chisel between the tiles and the concrete, hammering them up with a 2-lb. maul.
After all the tile is broken up, spread thin-set mortar over the concrete to level and smooth it before laying the new floor.
There’s no easy way to do this. Unlike tile on cement board or wood, there’s no underlayment or subfloor that can be pried up and thrown away. Removing tile from concrete requires knocking out the tiles and adhesive. It takes time and hard work. Even a small bathroom will take half a day, at a minimum.
Use a 3/4- or 1-in. masonry chisel and a 2-lb. hand maul. Start at a broken tile or between tiles where the grout has loosened. Work the chisel under the tiles, forcing them loose. Strike the face of stubborn tiles to break them up for easier removal. Wear safety glasses, gloves, pants and a long-sleeve shirt, since hammering the tile sends sharp shards flying. Also wear a dust mask.
Typically, older floors with mastic adhesive will come up easier than floors laid with thinset mortar. Rent a small jackhammer with a chisel point if the tile refuses to come loose. For larger rooms, consider renting an electric tile stripper.
After you remove the tiles, chisel and scrape the adhesive off the concrete as well. If you can’t get it all, don’t worry. You can leave bits of adhesive up to 1/8 in. thick. Then use the flat side of a 12-in. trowel to apply a 1/8-in. layer of latex thin-set mortar over the floor. This is to fill in voids and level around remaining bits of adhesive. If you’re installing new tile, use the same latex thin-set to set the tile. Thin-set holds ceramic tiles better than mastic and is easier to work with.
Keep in mind that the easiest solution of all is to leave the old tile in place and install new tile directly over the old. The new floor will be slightly higher, so you’ll have to trim the door and extend the toilet ring. For more details, talk with an expert at a local tile store