Do we have to replace Hollow Sounding Tiles?


Actually we have installed a Baltic grey marble in our projects and when we checked the tiles after installation hollow sounds not found in this stage. But when we reach to the snagging stage to our project, our quality team found some hollow sound in the tiles but all of them were “spots” so that we didn’t find any tile was fully not bonded, the unbonded area in the tile mostly not exceeds 20 to 25% from the whole area of the defective tiles. The issue is to replace these tiles might be a big issue from time and cost point of view, considering that we didn’t find any one of those tiles are broken due to this reason. Please note that these tiles are installed in the pedestrian areas only and there is not heavy loads are expected in these areas.

Please advice, do we have to replace all of these tiles? Or there is another acceptance criteria we can follow in this case.?

Appreciating your reply,


ANSWER - It could be that there are voids under those portions of the tile where they sound hollow.  Hollow sounds are not a defect, but they could be a symptom of a defect.   Hollow sounds are not necessarily a void or an indication the tile isn't bonded there, but it could be.   The only way to know for sure is to remove some tiles and inspect the underlying conditions.

The standards for stone in a commercial setting is that it should have 95% adhesive contact between the back of the tile and its substrate.  You can have up to 5% voids, but you can't have any voids along the edges or corners and any one void cannot be any larger than 2 square inches (size of golf ball).

If you have 20% to 25% voids under those stones then those spots can be susceptible to damage from heavy live loads or from dropping something heavy on those spots.   You may or may not have problems over time; it just depends if those tiles are subjected to more stress than they can resist.

If you don't see any resultant damages, then I would leave them installed.  You may or may not have a problem in the future.  Make sure you have some attic stock available so if they ever do become damaged you can replace them with a matching stone.

3 thoughts on “Do we have to replace Hollow Sounding Tiles?

  1. Mohamed Youssef says:

    Thanks for your answer.
    just I would like to clarify that the method we followed in stone installation was using semi-dry sand/cement mortar, we didn’t apply the thin-set mortar. According to that, there is any differences in the acceptance criteria in this case?.
    best regards

  2. Donato Pompo says:

    If the tile was installed in a dry-pack mortar and fresh set using a slurry bond coat, and then beat into place, then if it was done correctly I would expect 100% contact and not voids.

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