Installers are many times called to look at a potential tile job where the owner or builder is looking for more than a tile installer. They are also looking for a fortune teller who will be able to determine the future. This may sound far-fetched, but it happens more often than you may think.
The job is 18x18 in. ceramic tile over a new concrete floor that has been curing for several months. The problem is that the slab has developed a significant crack, which begins at a ninety-degree outside corner in the room and continues across the entire width of the proposed floor. The builder says that “Concrete will always crack like that, but not to worry, the tile installation will not be affected by it.”
As most of us know from extensive (and expensive) experience, this is not the case. That crack developed due to the concrete shrinking as it cures, especially from the stress of the outside corner. One important note here is that the concrete finisher failed to follow the American Concrete Institute (ACI) guidelines, which calls for the concrete to be cut. The concrete should be saw cut as soon as the concrete is walkable, but no later than 24 hours after the pour.
The TCNA Handbook defines this joint as follows: “Contraction/control joint—Formed, sawed or tooled groove in a concrete structure to create a weakened plane and regulate the location of cracking resulting from the dimensional change of different parts of the structure. Also referred to as a saw-cut joint.”
This job should have included an ANSI A118.12 Crack Isolation Membrane. Unfortunately on this job, neither the builder nor the owner would approve or pay for the use of this membrane, which leaves the tile installer in a tough place. Install the tile without the membrane and hope it doesn’t crack, or install the membrane and eat the cost.
As you can see in the photo, the installer went for the first choice which resulted in cracked tile across the entire room. He now has to replace the broken tiles, but they most likely will crack again. So does he absorb the cost of the membrane the second time to ensure a crack-free installation? It would be best if he did. But had he insisted that a membrane be used in the beginning, he wouldn’t be here on an expensive—and reputation-damaging—call back.