QUESTIONMy main floor tiles are 19x39” and cover approx. 900 sq. ft. These tiles have been installed using a “spot bond” method which has been confirmed by TTMAC to be an un-acceptable installation method. We discovered this issue when we started to notice that the grout lines were all cracked and then noticed that the edges of the tiles actually flex when stepped on. Some tiles have also started to become dis-bonded and click when stepped on…
We are working with our builder to rectify this issue but I have concerns with their proposed method of repair.
First off, the builder is proposing to remove only selected tiles which are currently showing signs of movement. My issue is that if all the tiles were installed via this spot bond method and this is not an approved method of installation, then all tiles should be removed and reinstalled properly. Further, even if a tile is not yet showing signs of movement, because maybe it is in a low traffic area, it will eventually start to move as well. Not to mention it would become dis-bonded just from the vibrations induced by removing surrounding tiles.
Secondly, the builder is proposing to leave the existing scratch coat in place and that new tiles would be installed onto this existing scratch coat. This seems very illogical to me and sounds more like another cost cutting measure. Would the removal of the existing tile not damage the scratch coat such that it would be required to do a complete removal right down to the sub-floor and start with a proper base?
Any feedback you could provide would be very much appreciated.
ANSWERANSWERS - it is not acceptable to spot bond tiles on floors. For residential dry area applications, tiles are suppose to have at least 80% thin-set contact with full support at all edges and corners. Tiles in wet areas should have at least 95% thin-set coverage. Areas of the tile that are unsupported are susceptible to damage if subjected to live loads.
The tile should not crack or flex, or become debonded. That suggests that the substrate is not stable and may have excessive deflection. To determine if the problem is an isolated condition or systemic, you have to remove and inspect tiles in different areas. If both the problem tiles and tiles without any sign of a problem are found to be deficient then you would likely need to replace all of the tiles.
I assume that when you say scratch coat you are referring to the mortar bed under the tile to which the tile is bonded. If after the tile is removed, if the mortar bed is structurally sound, it can be reused if properly prepared. If the problem resides in the substrate because of excessive deflection, then you have to repair the substrate.