Why do installations tent after a number of years?
How long it takes tile to tent is directly a function of at least three variables – the rate of concrete shrinkage, the shear strength of the thinset, and any expansive forces applied to the tile layer (heat for example). When the tile is poorly bonded, the tile can tent very quickly. If there is a strong bond, often the grout will compress significantly before the tile will lose its bond. Of course the type of tile is important as well – thinset has a harder time bonding to porcelain than most other tile. At the other extreme, I have seen a saltillo installation where the tile did not tent but rather spalled as the thinset and grout were stronger than the tile. When tile fails with a loud report, this certainly indicates that a good bond was present. Only when the shear force exceeds the strength of the bond, will the tile let go. Frequently, either the tile or the concrete will be without thinset residue – as if the thinset was not applied correctly originally. Usually, if the tile i
