The easiest way to get rid of an old tiled floor is just to put new tile right over it. But if the added thickness is a problem or the existing tile isn't well attached, then that old layer should be removed.
In small areas that are only a few feet square, a hammer and a cold chisel will do the job—eventually. On bigger jobs, a tool known as a demolition hammer is a better bet. With a cold-chisel bit chucked in its jaws, this miniature electric jackhammer delivers about 1,000 strikes per minute, working far faster than any would-be John Henry could pound by hand. The hammering action starts only when the chisel tip is pushed against a hard surface, so the operator remains in full control, with minimal fatigue. You can rent one of these tools (and chisels) for about $70 a day. In most cases, you won't even need it for that long.
Whether you decide to work by hand or get a power assist, you still follow these steps.
1. Protect yourself. Wear goggles, gloves, and a dust mask. Tent the work area in plastic to keep the gritty dust from infiltrating the rest of the house.
2. Attack the grout first. Plunge the chisel vertically into the joint, then tilt it at a 60-degree angle to the surface and plow it through all the grout lines. (With a demolition hammer, you can rotate the chisel into a position that lets you hold the tool comfortably.) Next to walls, where an angled chisel can't reach the grout, or near edges where you risk overshooting the tile, position the chisel vertically as you bust out the grout.
3. Get under the tile. Some tiles may pop loose as the grout is removed. Remove the rest by placing the chisel as close to the floor as you can and hammering it under the edge of a tile. The lower you can get the chisel, the easier the tile will come up without damaging the substrate. Work from the middle of the floor toward the edges, until all the tiles are up.
TIP: After mixing up a batch of thinset, let it sit (slake)
for 5 to 10 minutes so the liquids and solids have a chance to fully interact. When it's ready, it should have the consistency of peanut butter.