Spray a tile and set it wet and set a dry tile.
Wall under tile is wet.
Learn how to prep a shower wall for tile.
The best way to tell if this is your problem is to push down on the floor around the drain.
Those areas are exposed to the most water so damage tends to spread quickly.
If you have damp patches bubbling paint crumbling plaster or powdery deposits on wall surfaces close to the floor rising damp is probably the culprit.
Before you start remember that using the correct trowel and mortar is critical to a successful tile project.
Simply prime the nmp with sbr primer and your ready to fix your tiles.
In the old days ceramic was soaked and then set with pure cement.
Wait a week and pop them both up.
Just the opposite for porcelain.
The bottom line is that drywall and this includes moisture resistant drywall should never be used behind tile in wet areas showers and tub shower combinations.
Do your own test.
Rising damp usually occurs in masonry.
Technically called a cementitious backer unit cbu well known brand names of tile backer include durock denshield hardiebacker and wonderboard.
Another way to tell is to examine the drain from underneath which can be accomplished in the crawlspace or the basement.
Floor or wall indoors or out tile type and size all.
Tile floors are beautiful durable and a fairly diy friendly option but for tile s good looks to really last it s vital to start with what you can t see the ideal underlayment.
If it gives this may be the problem.
The ultimate goal of preparing a wall for tile is to create a flat dry solid structurally sound surface firmly attached to the wall studs with no flexibility or movement that could damage installed tile and grout.
For wet areas such as shower walls you must take certain precautions.
You want your cuts dry your tile dry.
If the plaster board is wet chances are there will be a big area not just the size of the tiles if your grouts cracked the plasterboard behind the grout is prob going to be wet aswell also if your silicone is discolouring this is also a signed of water damage you need to replace the damage boards but replace them with aqua panel or hardi backer as these are designed for wetrooms and are water repelent.
In addition because showers and bathtubs are wet areas they need a substrate that will not be damaged by moisture just in case a crack in the tile or grout lets water through to the backer.
I think this is a good one for mr gobis.
Leaking drainpipes in a shower or a bathroom plug will let water underneath tile.
Cement bonds better if it can dry slowly.
Hi my advice would be to make sure that the wet wall is extremely well fixed and then cover it in 6mm no more ply nmp which will provide you with a first class substrate.