Marble installed over hardibacker, but didn't get bond


Resin Back Stone Debonding - I have a 18" marble installed over hardibacker, the marble has a mesh that was slurried on back with some kind of epoxy or glue did not get a bond with the marble thinset the distributer said it would be ok to install with latex type marble -granite. There are other floors that meet up and no problems on them. i feel the barrier on back is the problem, can you respond?


ANSWER - The coating on the back of the stone is likely a resin back that is applied to some type of stones that are more fragile. It may have a fiberglass mesh suspended within the resin or not. The type of resin used for these stones can vary and some can be bonded with a modified thin-set and some can't. The resins that contain paraffin have not bonded well in the past. It isn't possible by looking at the resin back to determine if it is bondable or not, it is necessary to test it.

The industry standards and the normal response from manufacturers of thin-set mortars is that an epoxy thin-set should be used to install resin back stones.

In some cases, some thin-set manufacturers will test specific resin back stones with their high performance polymer or latex modified thin-sets and if the results are good enough they will recommend the respective thin-set for the particular resin back stone.

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