Many homeowners have asked me, “Why do floor tiles loosen?” It’s amazing to me, with the advances in floor preparation and modified mastics, that tiles can still come loose. It is possible to understand why floor tiles come loose without employing the help of a flooring professional or general contractor. Allow me to tell you why this happens.
First, it is important to understand what holds the tile to the floor. Tiles, whether made of ceramic, porcelain, slate, granite, or marble, are all held in place by a substance called thin set. Thin set is a Portland cement based material containing a special blend of additives which give the mixture the ability to gently flex under strain and return to its original position. This strain, also known as load, can be the result of climatic changes, such as the passing of the seasons, or from a physical nature, such as the weight of a person or item placed on the tile.
Sometimes the strain or load can be too much for the thin set. If a heavy object is placed on the tile floor, such as a piano, it is very possible to overload an individual tile. If this happens, the bond between the tile and the thin set can be broken and the tile can sheer away. Once sheered, the tile will never re-bond with the thin set. The result is a loose tile only held in place by the grout surrounding its four sides.
Next, the structure of the floor needs to be considered. Before installing any type of tile floor, the contractor or flooring professional should survey the sub floor. The sub floor must be built rigid enough to support its own weight, the weight of the tile, and the weight of the items placed on it. Most local codes state that if the floor is framed with 2×8 floor joists, 16″ on center, and sheeted with a 5/8″ plywood material, it can be tiled. Remember, before starting any construction project, check with your local building code officials. Better safe than sorry.
In many homes, the floor just isn’t built or framed strong enough to support its own weight and the weight of a tile floor. When floors are not framed sufficiently they tend to move perpendicular to the plane of the earth. This up and down motion stresses the bond between the tile and the thin by as applying too much weight or load in one area.
The bond between the tile and the thin set may very well be strong enough to accept an overload a few times. The number of times is directly related to the quality of the thin set. Inevitably, even the most expensive thin sets will fail if subjected to continual overloading.
Last, the most common reason why a tile will loosen from its thin set is improper installation. Careless contractors tend to tile weak floors. The thin set needs to be mixed according to manufacturer specification. If mixed too wet or too dry, the thin set will not properly cure. This improper curing results in a weak floor.
Over time, most tiled floors will have a tile pop loose. This is to be expected and can be repaired. If over the life of a floor, many tiles pop loose, a more serious problem is the cause. In my experience, human error is the cause.