Tips for Installing Tile Over a Concrete Slab

A dull concrete slab can be made into an enticing patio surface by putting tile on top of it. If installed correctly, a tile surface will last for decades and will require little maintenance. Choose tiles made for exterior surfaces. Avoid glazed tiles because they will be slippery. Quarry tile makes a good choice, as do flagstone, paving brick, and concrete pavers.

Inspect and Prepare the Concrete

Installing a new tile surface can straighten out a concrete slab but will not add strength. If the old concrete is loose or wobbly, do not tile over it until it has been repaired. Fill in low spots, cracks, and small holes with patching concrete. To straighten out large areas, combine dry sand with Portland cement. Mix with water, patch, and trowel smooth. Allow several days for it to cure. Clean the concrete thoroughly and brush on latex concrete bonder. Allow it to dry.

Lay Out the Job

Use a chalk line and a framing square or a piece of plywood with two factory edges to establish perpendicular layout lines. Plan well to avoid any slivers at the edges of the patio. If the slab is out of square, try to make it as inconspicuous as possible.

Before you mix the mortar, do a dry run in which you lay out most of the tiles in position to make sure you have chosen the best placement.

Mix and Spread Adhesive

For a large job, you’ll thank yourself for renting a heavy-duty drill that has a mixing blade. Pour the thinset and latex liquid into a 5-gallon bucket, set the mixing blade in, and grip the bottom of the bucket with your feet to keep it from spinning as you run the drill. Mix thoroughly to a toothpaste consistency, let it sit for 10 minutes, then mix again. Have a bucket of water on hand for mixing and to set the blade in when you aren’t using it.

Work in 3- to 4-foot-square sections. Do not cover the layout lines. Trowel on a smooth coat, then go over it with the notched part of the trowel. Make grooves but do not let the notches go all the way down to the concrete. Whenever possible, use long, sweeping strokes and keep the surface level.

Set the Tiles

Lay the tiles instead of sliding them into place. Give each a light tap with a mallet. Use plastic spacers to maintain even grout lines and follow your layout lines precisely. To make sure you end up with a smooth surface, use a flat piece of plywood about 16 inches square. Periodically, set it on top of the tiles and tap with the mallet.

Cut Tiles

For straight cuts on tiles, a standard tile cutter will do the job. Making a cutout or notch is more difficult. If you have only a few to make, you can use a tile cutter to cut the tile twice and install two pieces instead of one. You will end up with a hairline joint that is inappropriate for interior surfaces but acceptable for a patio.

If you need to cut pavers or stone, or if you want a more professional-looking cutout or notch, rent a wet tile-cutting saw. It easily and cleanly slices through any masonry material. Always keep the water running on the blade, or it will burn out.

Grout and Clean

Allow the mortar to set for a day or two, and remove the plastic spacers. Use the latex additive with the grout. On a large surface, it helps to drag a heavy, wet towel across the surface after the grout has been applied

Clean the surface with a sponge, watching the grout lines carefully as you work. After everything is dry, buff the surface with a dry cloth.