PVA and why you shouldn't use it as a tiling primer.

[gcol]

Hard to say. Were the walls dusty? What is certain is that you can't do anything about it now. You'll probably be ok.

 

[Nestor_Kelebay]

If you used a cement based grout, what I want you to do now is give the grout two weeks to dry, and then use an artist's paint brush to paint an acrylic grout sealer onto your grout lines. That will provide a clear coating over your grout to prevent mildew from growing in/on it. Your bathroom tiling will look new for many many years if you seal your grout.

 

[gaz2923]

i wasnt worried about it not staying white i was more worried about the adhesive not lasting and them falling off

 

[gcol]

So.......were the walls dusty? If you could lightly rub your fingers on the surface and get powder left on them then it's unlikely that you'll have a proper bond in those areas. I'd still like to bet that the bond will be good enough to stay put though.
What Nestor says was "on topic", if you were to seal the grout then it would help in keeping moisture out from the back of the tiles and making matters worse.

 

[Nestor_Kelebay]

Sorry for coming across as real dumb, but where I live I think it's actually pretty common for people to set tiles directly over ordinary non-waterproof drywall (what you call "plasterboard") in a bathroom shower.

I'm not saying I think that's OK. I use cement board and set my tiles with thin set in all of my own bathrooms. I'm just saying that I redid the tiling in my sister's house and I took down tiles that were set in mastic over ordinary drywall. I fully expect all of the houses in her neighborhood were done that way.

Her house was built in the 70's, she bought it in 1985 and and I retiled her bathroom in the mid-90's. I don't know if the bathroom was retiled prior to her buying it. I also don't know whether she had baths instead of showers.

 

[gaz2923]

ahh i see, right well i shall go ahead and seal them in then