QUESTIONWe are installing a new steam shower and had these concerns about the tile work. (1) We had learned he used sanded grout and have someone new who is removing it to re-grout with epoxy. (2) When the new worker removed a few tiles damaged in removing grout he discovered the tiles popped right off the wall and we all saw the strange way the tiles were mounted to the wall.
Can you tell us if this is some version of Spot Bonding? Can you give us some feedback? If it is Spot Bonding, don't we need to have the tiles re-installed before we re-grout with epoxy grout?
We appreciate any assistance you can give. We want our new steam shower to help us be more healthy, not to make us sick!
ANSWERANSWER - First of all there is nothing wrong with using sanded grout as long as the grout joint width is 1/8" or wider. There are some benefits to using an epoxy grout in terms of stain resistance and maintenance. Although, if the epoxy grout isn't installed correctly with an experienced installer the grout can cause more maintenance and be less appealing aesthetically.
To remove existing grout is not an easy process and there is always the risks of damaging tiles during the grout removal process. We normally expect tiles to be tenaciously attached to their substrate. Although the standards only require a shear bond strength of 50 psi. If the tile is pried off the wall then it is being subjected to both shear and tensile stress through leveraging that can be beyond what it can resist. So it isn't clear whether the tile is bonded adequately or not.
Your link to a photo didn't work, so I can't see if the tile appears to be spot bonded or not. For shower applications the standards require that there is 95% contact between the back of the tile and its substrate. In theory, the less adhesive contact the less the overall bond strength. Today's thin-set modified mortars can reach over 300 psi bond strength. So even if there were only 50% contact, it would meet the bond strength requirement, although it would still not meet the thin-set contract requirement.
It would be best to verify whether your tiles are bonded adequately or not before you re-grout with epoxy. You don't want to spend the money on re-grouting only to have to then deal with a tile debonding problem. The only way to accurately determine if the tiles are bonded well enough is to test them for their bond strength. You should hire a forensic tile expert to evaluate your situation, although the cost for doing so may or may not be prohibitive and not practical for your situation.