QUESTION

Hello! Any advice you have would be greatly appreciated. We built our home 8 years ago. Last year we had several tiles tent in our kitchen. We had the tiles replaced with our leftover tile by the company that installed it. When the tiles were lifted, most came out in-tact and clean of thin-set on the bottom of the tiles. There was thin-set noted on the concrete floor which proved very difficult for the tile professionals to remove. They were able to replace the tile. No foundation cracks were found and no water damage was present. Almost a year later, we just had this occur in a different area in our kitchen. At least 8-10 tiles are affected. The grout is crumbling, the tiles tented/have fallen back down and bounce when you walk on them. We have also noted several hollow tiles throughout our home. There is no pattern to this, some stand alone, some are in a cluster. The hollowed tiles occur in all rooms with tile. (master bath, kitchen, fireplace, and guest bath). All other floors (hardwood and carpet) have had no issues. We have counted at least 85 hollow tiles. Any thoughts? Thank you in advance!

ANSWER

ANSWER -  When tiles tent/buckle up it is normally due to the combination of lack of resilient movement joints and due to the tile not being bonded as well as it should.

Movement joints are grout joints that are filled with an ASTM C920 resilient sealant (caulking) so that they will diminish the stress in the tile installation that will naturally occur due to thermal expansion and contraction within the tile and moisture movement from the tile absorbing moisture.  The standards state that all perimeters and transitions within the tile installation should have movement joints, and any span longer than 24' for interior areas should have a movement joint; unless the interior area is near windows or skylights then the span should not be less than every 12 feet.

Because the hollow sounding tile was easy to remove and the thin-set adhesive didn't bond to the back of the tile, and because the grout was cracked around the hollow sounding tile, more than likely the tile was loose and was not bonded well.  Perhaps the installer spread his thin-set too far in advance and it skimmed over and it didn't bond well.  Or maybe the back of the tile had a contaminate on it.

Although hollow tile in itself is not a defect as the hollow sound can be caused by different conditions, it can be a symptom of a problem.  Chances are the tile wasn't bonded well enough and then the lack of movement joints caused the tile to be subjected to more stress than the tile could withstand, so that stress caused the tile to loose bond and the loose tile caused the grout to crack.

That is only a guess.  A forensic inspection with testing would have to be performed to verify what caused the failure.

There isn't much you can do to remediate your problem, other than replace the those tiles and install them properly.