I realize a bathroom in an old house (1900) in a room with tomette upstairs. then seal this coating without having to remove all the tiles! (light weight on flying floor!).
A bathroom is not a pool! As such tomettes are already waterproof and the joints are usually very thin. It may be necessary to look at the skirting board and add a silicone seal. A good surface treatment of the tomettes, if only with the wax will do the rest! Now if you want to wade, there is no other solution than to remove everything and redo a screed with waterproof barrier (polyane) back on the skirting boards, then rest of the tiles...
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