QUESTIONAre some hollow tiles a problem? A year ago, we were rebuilding the bathroom and the floor in the hallway in our blockhouse apartment. When the floor in the hallway was freshly laid, then about 3 hours later I had to walk over the ceramic tiles with my wife, because we needed to go to the hospital. After all the work was finished, the tiles showed no defects or hollow spaces. About a month ago I noticed that the tiles (about 10 pieces), in the area where we walked over, had voids beneath it. The tiles are not moving, the joints are completely intact. The tiles are laid over a concrete slab. Is it necessary to replace those hollow tiles, or are these few tiles (about 10% of the surface mostly concentrated in one specific area) not a problem for the integrity of the floor? In case of repairing those tiles, do we have to remove and replace the defect tiles or is it enough by injecting epoxy under it? Thank you in advance for your answer.
ANSWERANSWER - Hollow sounding tile is not a defect per industry standards. Although a hollow sounding tile can be a symptom of a defect.
If all of the floor sounds hollow or a portion of the floor sounds hollow, then it might be due to the materials and configuration of the tile assembly below. Membranes will normally cause a hollow sound.
If only a portion of a tile is hollow sounding or only certain tiles are hollow sounding it could be that there is a void under the tile or that the tile is not bonded in those spots for some reason.
If is possible that if you walked on a tile installation before it was substantially cured, it could cause the tiles to release or to compromise the tile's adhesion. In the later case, then perhaps a year later the tiles were subjected to some stress and those tiles were not able to resist it due to the diminished bond strength. Lack of movement joints could be a reason the tiles were subjected to stress.
If there is no resultant damages to the tile or grout, then I would just let it go. Make sure you have extra tile for the future just in case they do get damaged you can replace them.
Injecting epoxy is not a legitimate repair. It is treating the symptom rather than the problem. I have never seen it solve a problem.