As a professional tiler you would think I know. I dont !! Is Epoxy grout more flexible than a cement grout ??? I assumed that grout gives under stress. My assumption of epoxy is it adheres to the tile more than cement grout. If there is movement the tiles would tent rather than the epoxy failing. Thats why I choose not to use it. I do expect some stick so fire away🙄🙄 Your never to old to learn or Im an idiot😀