Straight Crack Across Tile Floor

Posted in Home Improvement on June 19, 2018

Some older houses have ceramic tile floors over a cement slab in their rooms. Sometimes the floor may crack over the entire length of the room. If you want to replace the tile, you might be asking yourself how to prevent the tile from cracking again.

If you have a crack that runs the entire length of a room in a relatively straight line, the problem is not in the tile, but in the subfloor. Any movement in the underlying subfloor will crack ceramic tiles. Cracks like these are almost always found over a joint in the cement slab.

Remove your cracked tiles and see if there is a "cold" (or "control") joint in the slab or if the slab was done in two pours. A cold joint will look like the joints you see in sidewalks and is there to relieve stress. If the slab was poured in two pours, you will see an almost perfectly straight crack, and the color of the cement may vary slightly from one side to the other.

Tiles laid over a joint or crack in the subfloor will have a tendency to crack, but if you're nailing, there are steps you can take to cut down the chances of it happening again.

If there is a joint in the slab, it should be an expansion joint. Make a 1/4-in. to 1/2-in. wide cut through the slab at the joint (use a rented concrete saw) and fill the cut with silicone caulk or asphalt-impregnated expansion joint filler.

Next, when you lay out your tile, make sure that no tiles straddle the joint. When you grout, don’t use regular grout over the expansion joint. Instead, use a caulk labeled specifically for tile floors (available from tile dealers). This will give you a joint that will take some movement without cracking.

If the cracked tiles are not over a joint, it means that your floor settled at some time, causing the tiles to crack. As long as the floor isn't actively settling, you can usually safely retile without having to worry about further cracking.