QUESTION

Should I replace the tiles that sound hollow? - i have tile installed on a concrete wall and all the tile in a one foot area sound hollow when they are tapped. Should these tile be removed and replaced?

ANSWER

ANSWER - When tapping tiles with hard objects you can get a different sounds depending on the conditions beneath the tile. Hollow sounding tile does not necessarily mean that the tile is not adequately attached to the concrete wall. You would have to do additional evaluation to determine what is causing the hollow sounds.

When some portions of a tile or tile application sounds hollow and other portions do not sound hollow, then it does become suspect. The hollow sound can emanate from any level of the tile assembly or its substrate beneath it. Applications over stud walls will tend to have a hollow sound. Applications over concrete block that isn't' filled with concrete can have a hollow sound. If there are voids in the thin-set adhesive bonding the tile then those spots could have a hollow sound. If there is a mortar bed beneath the tile that has debonded you can get a hollow sound. If the substrate changes within a tiled area there can be a difference in sound. If a natural stone has cleaves that have separated they can sound hollow.

If there is no evidence that the tile is loose or not adequately attached, then that might not justify removing those tiles. That spot on the concrete wall might represent a void within the concrete and it may or may be detrimental to the long term performance of the tile installation. To determine the cause of the hollow sound you would have to intrusively remove those tiles to see what the conditions are beneath it.