Tile Over Plaster Walls

Both painted and bare plaster allows for the installation of tile.
Tile over plaster walls. If plaster is any way compromised you should tear out to studs and start over. If you re not sure if you have lead paint test kits are available. Loose paint must be scraped. But with cement board.
Can you lay tile on plaster walls. Scrub the wall tiles with diluted degreasing cleaner and a nylon scrub brush. Don t use paint glue pva wall paper paste only use the primer recommended by the adhesive manufacturer of your chosen tile adhesive. Cover with cement board tape off.
Bring plumbing to code. Or flatten walls with a latex modified skim coat product. You may tile over existing tile painted or unpainted drywall plaster and textured walls. Testing the wall for durability.
The problem otherwise is that grout is porous and any slight crack will cause moisture and mold on any other surface. That is true you cannot tile over plaster if that s your plan. It used to be very common to put tile up on whatever the wall was and seal the the tile. Mix degreasing cleaner with water in a bucket using a dilution recommended by the cleaner manufacturer.
Not all plaster wall surfaces will support the tile properly. I have repaired tile jobs that were over 20 years old that the tile was applied directly to regular sheetrock and plaster walls. You should not tile over wallpaper glossy surfaces lead paint or plywood. You would have to remove the plaster and replace it not with drywall run from a contractor who says that.
This was back in the 80 s. Layer newspaper on the floor across the bottom of the tiled wall. Also now it s been plastered you will be restricting yourself to a tile with a max weight of about 16 kg m2. However tiling over tile can add quite a bit of thickness so make sure your wall can handle the weight.
Add a diverter and shower line in the wall. Follow manufacturer instructions to a tee.