Due to 88 years of settling, the glazed ceramic tile walls in my bathroom have pulled away from each other at two corners, leaving a gap 1/2 to 3/4 of an inch wide by one inch deep. I have a similar, though less drastic opening where one wall meets the floor.
The tile is otherwise in decent shape, and the lines are relatively straight. But the gap exceeds the recommended opening for both grout and caulk that I have seen.
Having just spent three hours digging out old, discolored caulk, my preference would be to use grout on the repair. The openings appear to have developed over an extended period of time; despite them, the walls appear to be quite stable.
Does anyone have any advice on materials, additives or technique?