QUESTION

we fixed the tile in our project but we found a sound when we knocking above the tiles, and we have to hand over this tile to the consultant, is there any specification or tolerance for the tile hollow sound?

ANSWER

There is no standard for whether a tile should sound hollow or not, or do what degree.   A hollow sound can mean the tile, or a portion of the tile, is not bonded or there is a void under that portion of the tile.  Or the hollow sound may be a characteristic of that particular tile assembly.   Unbonded mortar beds have a different sound than bonded mortar beds.  Tile installed over wood subfloors have a different sound than tile installed over a concrete slab that gives more of a solid should.  Tiles bonded to membranes have a different sound.  Voids in the substrate, or substrates that are not bonded, will also give a hollow sound.

Generally speaking when only some of the tiles have a different sound, discerned to be a hollow sound, it might mean the tile has a void under it or that something is not bonded or you may be hearing a condition within in the substrate itself.   It doesn’t necessarily mean you have a problem.   A hollow sounding tile might be adequately bonded and it might perform as intended.   On the other hand, the hollow sound might be a symptom of an underlying problem.

The only way to determine if the hollow sound is a problem or not, is to perform an intrusive inspection by removing various tiles under various conditions, performing some bond strength tests, and having an expert, such as CTaSC, evaluate the conditions and findings.