What Causes Ceramic Floor Tiles to Crack?

Ceramic tiles come in seemingly limitless sizes, colours and shapes. They are an economical, and often more durable, alternative to real stone and provide superior resistance to wear than other types of flooring materials, such as wood or carpet. Ceramic tiles should not crack under normal usage, and, when they do, it is almost always due to one of the following:

Inadequate Mortar

Ceramic floor tiles, especially larger tiles, need an even distribution of mortar underneath them. Voids in the mortar under the tile allow the tile to flex and crack. As a general rule, tiles larger than 12×12 inches should have mortar applied to the back of the tile as well as the floor to help ensure adequate coverage.

Improper Subfloor

Ceramic tile laid over plywood is more susceptible to cracking due to the flexible nature of the plywood. As the plywood under the tiles flexes, especially along floor joists, the flexing can cause the floor tiles to crack.

The best subfloor for ceramic tile is a mud bed, which is a specially prepared floor made of several inches of concrete reinforced with wire mesh. Where that is not possible, using a cement backer board over plywood can provide much of the same stability benefits of a mud bed.

Missing Underlayment

Tile installed directly on concrete floors will mirror any cracks in the floor. Once a tile is cemented in place with mortar, if the floor cracks, that crack will radiate up through the tile. Tiles laid over existing cracks usually crack due to uneven floor movement along the tile.

To counter this, an uncoupling membrane is applied to the concrete before the tile is installed. This membrane bonds to the concrete floor which then bonds to the tile. The flexible membrane can accommodate movement in the floor without telegraphing it through the tile in the form of cracks.

Heavy Objects

While tile is generally more durable than wood, carpet or linoleum floors, dropping heavy or even hard objects on the tile can cause it to crack.

Faulty Tile

The overwhelming majority of tiles sold today have no manufacturer defects and will not crack if properly installed. Once in a while, however, you may run across a tile that was improperly fired or contains contaminants that weaken the strength of the tile, leading to cracking after the installation.

While tile is an extremely durable material, cracking can occasionally occur. The factors mentioned above can lead to cracking of other tile types such as glass, natural stone, marble, terracotta, slate, and others. Wall tiles can also be affected by these same deficiencies.

Source: Homeservice Club of Canada