We recently installed tile in our kitchen. It's upstairs in a 50 year-old home. We knew the floor was "soft" in that it had saggy spots and we had access to most of the joists. We shored those suckers up as best we could and laid the tile. We used tile adhesive rather than thin-set believing (perhaps erroneously) that it would accomodate any latent flexibility in the floor.

Everything looked and felt great until about 2 weeks later when we began to notice spots where the grout was crumbling. Not everywhere, just a few spots. We corrected some of the problems with additional shoring, but others aren't going away.

You can't actually feel the "softness" of the floor. It appears to be just enough flex to ruin the grout.

Will an epoxy grout (or any other product!) solve this problem, or are we doomed?

  • 1
    what type of tiles and what is underneath the tiles (underlaymment)?
    – joe
    Jul 23, 2017 at 3:36
  • Ceramic floor tile, common from Home Depot. The underlayment is Melamine.
    – JBH
    Jul 23, 2017 at 5:12
  • Sacrilege (but then, so is a flexible underlayment) but I wonder if caulking as grout could work.
    – Ecnerwal
    Jul 23, 2017 at 15:46
  • Caulk is an interesting idea. Does it shrink like adhesives?
    – JBH
    Jul 23, 2017 at 18:23
  • 1
    There's silicone-based grout (pretty similar to caulk), which remains flexible. That will solve the crumbling grout problem. However, the movement that is crumbling your grout is a problem for the tiles. They have zero give. So you will get either tiles popping loose or tiles cracking.
    – fixer1234
    Dec 5, 2017 at 10:01

1 Answer 1


You could try adding a latex or other type of flexibility modifier to the grout.

The number one rule of ceramic tile is the base has to be solid. If the floor flexes the installation will fail sooner or later.

Good luck!


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