I just finished installing my first tile floor in my small bathroom (28 s.f.) The house is about 80 years old, and of course, the room isn't square. I used 6 x 24 tiles, and now that they are all down, I can see a slight shift. I put a 5' level as a straight edge along the 7' length, and it appears that 1 course of tiles shifts about 1/8" (the width of the grout line). Just that little amount looks off tremendously, however. The other problem that I had was putting down the Hardibacker. the room has a radiator that is built into the wall. I put hardibacker under the radiator but couldn't screw it in place because it wasn't accessible. There is noticable slope in the floor from under the radiator. I'm not worried about that visually or from a safety perspective because it is right next to the toilet and it won't be visible. I am worried if the tile will crack or the toilet will leak.
So, do I tear out the whole job and start over? Is there a fix for a course of tiles that have shifted? It the slope really a concern? Thanks!