The problem otherwise is that grout is porous and any slight crack will cause moisture and mold on any other surface.
Tiling over plaster walls bathroom.
It used to be very common to put tile up on whatever the wall was and seal the the tile.
It is important to check the weight of your tiles as plaster skim has a 20kg per square meter weight ratio.
You would have to remove the plaster and replace it not with drywall run from a contractor who says that.
However tiling over tile can add quite a bit of thickness so make sure your wall can handle the weight.
The adhesive and tile will block moisture from evaporating.
Bring plumbing to code.
This was back in the 80 s.
You may tile over existing tile painted or unpainted drywall plaster and textured walls.
But with cement board.
You may not have lathe but compressed board under the plaster and scratch coat.
You should not tile over wallpaper glossy surfaces lead paint or plywood.
Follow manufacturer instructions to a tee.
If plaster is any way compromised you should tear out to studs and start over.
Cover with cement board tape off.
Tiling on a plaster wall tiling on plaster.
Add a diverter and shower line in the wall.
I have repaired tile jobs that were over 20 years old that the tile was applied directly to regular sheetrock and plaster walls.
If you re not sure if you have lead paint test kits are available.
Fresh plaster whether applied as a patch or to the entire wall must dry completely before tile is applied.
If you have a tiling job to do in your bathroom and the walls have been skimmed with plaster you have.