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Wednesday, June 12, 2024

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HomeTechnicalAsk the ExpertsWhat causes blistering of tile over existing terrazzo flooring?

What causes blistering of tile over existing terrazzo flooring?


Attached are two pictures from a project. Both are on-grade over existing cement terrazzo flooring. Obviously, one has spot bonding. The other one, well, I have never seen before – literally the tile
has blistered upwards. A video of the project shows that it still sounds solid in most of the areas, but you can hear hollowness in a 1/2″ area. 

Have you ever seen a glazed product do this? Can spot bonding shrink down so hard at the perimeter of each blob to literally bend the tile?

We will remove some pieces and a few more to verify the substrate when we are there onsite. I believe it was a two-part thinset. I will place a straight edge across it to see if I can see light. I suspect the mortar pulled the tile down. I do not know if it’s porcelain or not. The distributor, I think, that supplied it is reputable though.

No one is being blamed. The owner is redoing the 12,500 sq.ft., but hoping the terrazzo is salvageable. 

There is some concern as maintenance department  replaced several tiles, and mentioned it smelled damp.


The Technical Team has been having a few discussions and thinks this looks like agglomerate tile. We think these are the sorts of issues that could occur with the agglomerate tile when spot bonded or with voids in the bond coat. And the damp smell could be an indicator of it being wet from who knows what, causing the tile to bubble.

One of our team has seen sort of similar issues on large agglomerate installations.

Thanks for sharing this with us and for keeping us updated! It helps build our knowledge base too! 

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