My tile is bonded to a concrete slab. Why do I have cracks?
While it is impossible to speculate on the exact cause of cracks without an inspection, some reasons for cracking include but are not limited to:
Whenever tile is bonded to concrete, movement in the concrete will cause cracks to occur in the tile layer.
Should cracks occur in the concrete, these cracks will “reflect” through the tile – this is often called “reflective cracking.” Similarly, if tile is installed over a control joint (The Tile Council of North America does not recommend this), movement in the control joint will cause a crack in the tile. Even small shrinkage cracks in concrete can be dimensionally active where continued curing of the slab will cause these cracks to expand or propagat. If this occurs, the cracks will show through the tile.
This type of cracking can be easily avoided – either by installing the tile on a mortar bed set over a cleavage membrane (for example, TCNA Handbook detail), or by installing the tile over a crack isolation membrane using a thinset method.
What is reflective cracking?
Whenever tile is bonded to concrete, cracks occurring in the concrete can cause cracks in the tile layer – this is often called “reflective cracking.”