How to Tile Over Concrete

Clean the concrete and remove baseboard, if any. If there was previous flooring, such as vinyl, remove it and scrape off debris with a floor scraper. If there is any oily substances on the concrete, clean it with an abrasive cleaner. Anything left on the concrete will be a deterrent for the adhesion of the new flooring. Check to make sure the floor is level. Minor problems can be corrected with the thin set mortar. If there is a major problem with the levelness of the floor, you need to put down a floor leveler. You can buy this at any home improvement store. Let the floor dry well before moving on to the next step.

Using the chalk line, set up the pattern for the floor tiles. Start at the longest wall you have. Floor tiles vary in size and shape and can be installed in different patterns. The chalk line works well when using square tiles in a straight line or on a diagonal. Lay a couple tiles down to see if you like the pattern you've chosen. If you're using rectangle tiles, the chalk line will only work if you're laying a straight line. Set the line to go over the threshold of the door, so when the door is closed you won't see the seam that meets up with the flooring from the other room.

Mix the thin set mortar. Follow the manufacturer's instructions on how to mix and how long to let it set. With the flat side of the trowel, place some mortar on the floor inside the chalk line for a tile. Then score the thin set with the other side of the trowel. The trowel should be held at a 45 degree angle for proper coverage. Place the tile and gently tap the tile with the rubber mallet. Set another tile and use a spacer between them to keep them uniform. Spacers come in different sizes depending on your preference. Spacing is generally kept between 1/4 and 5/16 of an inch. After a few tiles, go back and pull one up. Check to make sure that at least 80% of the tile is covered by the thin set. If not, increase your thin set. If too much is coming up between the tiles, decrease your coverage of the thin set.

Make the cuts. There are two schools of thought on the cut tiles. The first is do it as you're going along; the other is to wait until you are done and go back when it's dry. Doing it as you go along, measure and mark the underside of the tile. Using a wet saw, cut along the line. If you are going around something circular, such as a toilet, you will have to use snips. Be careful using snips as the tiles crack easily. Cutting after all the whole tiles are installed means you can make all your measurements at once, go cut, come back and finish. It also means you may have to walk over the installed tiles. Make sure they are relatively dry. When you have to step on them, step toward the center. Either way, follow manufacturer's instructions on how long to let the thin set dry before grouting. When the tiles are dry, remove the spacers.

Mix the grout. Using a grout float, place a glob of grout on the tile and push it around the openings. Then go over it again, this time to remove excess grout. Do a section and then wipe it down with water and a sponge. Repeat until you have the whole floor grouted. Let dry fully--this usually takes 24 to 48 hours.

Seal the gout. There are many types of grout sealers on the market. Some are a liquid that gets sponged on, and some are a spray. Use the one that is best suited for your particular tiling project. Make sure to seal the grout well to prevent staining and soiling. Done properly, your new tile floor will look new for a long time to come.