It used to be very common to put tile up on whatever the wall was and seal the the tile.
Tile over plaster walls.
Mix degreasing cleaner with water in a bucket using a dilution recommended by the cleaner manufacturer.
Then rinse the wall with a water dampened.
Can you lay tile on plaster walls.
Not all plaster wall surfaces will support the tile properly.
Add a diverter and shower line in the wall.
Scrub the wall tiles with diluted degreasing cleaner and a nylon scrub brush.
I have repaired tile jobs that were over 20 years old that the tile was applied directly to regular sheetrock and plaster walls.
You may tile over existing tile painted or unpainted drywall plaster and textured walls.
Adhesive grout and tile 20kg max weight onto plaster.
Mold does not grow on cement.
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.
Bring plumbing to code.
Both painted and bare plaster allows for the installation of tile.
You would have to remove the plaster and replace it not with drywall run from a contractor who says that.
Layer newspaper on the floor across the bottom of the tiled wall.
Cover with cement board tape off.
If you re not sure if you have lead paint test kits are available.
Follow manufacturer instructions to a tee.
You should not tile over wallpaper glossy surfaces lead paint or plywood.
If plaster is any way compromised you should tear out to studs and start over.
Don t use paint glue pva wall paper paste only use the primer recommended by the adhesive manufacturer of your chosen tile adhesive.
But with cement board.
The problem otherwise is that grout is porous and any slight crack will cause moisture and mold on any other surface.
Loose paint must be scraped.
Testing the wall for durability.