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I have a downstairs w/c that has been tiled from top to bottom. The window wall is where the toilet and cistern are and the bottom 5 tiles keep coming off the wall for whatever reason I don't know why. I have used the same adhesive throughout the entire room, but only these tiles come away, leaving some of the adhesive still on the wall.

I know that water hits them and the grout, and there will be some condensation in there too, all of which will contribute to turning the white grouting a yellowish brown colour.

This patch of wall to the touch feels much colder than any other parts of the same wall, so rather than tiling over it again, I wanted to ask if there is anything I could put on this area of wall before I tile it again.

In other parts of the house, whenever we needed to decorate on this side of the house, we have had to PVA the walls in a 50/50 water & PVA mix before we plaster or paint, so maybe it's as simple as a bit of PVA?

If not, I don't know what to use and would appreciate any tips on what to do to stop the tiles coming back off the wall.

Hi,

You mention that the grout in the affected area is yellowish brown, this would indicate to me that the area behind is saturated with water.
As you will no doubt be aware, water will always follow the path of least resistance downward, hence the lower part of the tiled wall is effected the most.
A number of factors are probably combining to create the current condition.
I would firstly ascertain whether the tiles are stuck to a solid or stud wall?
Whichever it is it, it isn't acting as a waterproof barrier to the moisture.
If it is a stud wall, then I would hasten a guess that it has been lined using normal plasterboard. It needs to be moisture resistant plasterboard, or WBP plywood.
If it is a solid wall then a breach in the grout, or from behind the pipework or the tray itself is causing the plaster behind it to absorb the water. Once there it has nowhere to go, the plaster swells and the tiles pop off.
Another thing to check is that the protective film has been removed from the shower tray prior to it being sealed with mastic (even better a product like CT1 or the Works these work on damp surfaces (even underwater!)).
Another thing is to check that the tiles used haven't required to be sealed, if they are a natural product.
The last thing is ventilation; the fitting of an extractor fan with a humidity sensor.
Simply retiling over the affected area simply traps the moisture, it will in time become more and more of a problem and spread. It will not go away and needs the cause not the symptom's dealt with. If you share the wall with a neighbour they will be suffering as well.
I would recommend using a dehumidifier in order to speed up the process.
Good luck, I hope this helps.
Kind regards,

Neil the Oxford handyman