My husband is retiling our shower and although he is taking off some tiles he wants to leave the back wall alone. Its tiled onto ply and is 1.m x 2.08m. I have chosen 300 x 400 tiles (around 20 tiles with cuts) and cannot find enough details on an adhesive that will do the job.
I have looked at so many manufacturer websites and I am now so confused I am off to lay down in a darkened room will some genius can advise.
I know most will say take off the tiles but its taken me a few years to get him round to redoing it in the first place!
any help would be much appreciated.

It is never a good idea to tile on tile unless you have absolutely no choice. Even worse you have ply on your bathroom wall to tile onto and you have a recipe for disaster.
Ply isn't a suitable substrate to tile onto in a bathroom as the moisture and heat can have an adverse effect and possibly de-bond you tiles. Add on to that the additional weight of your new tiles, adhesive and grout and you could be looking at serious and potentially dangerous consequences!
You would be much better to rip out the ply and put up a proprietary tile backer board such as Hardie, Wedi/Marmox type boards or Aquapanel.

Oh and welcome to the forums.

thank you- you are aptly named!
We were discussing this over dinner and I did mention taking down the wall but as my husband said he would still have to get the tiles off to get at the screws that held the ply on, now having read your post it does seem that there is no quick fix!

Hi and welcome..

as above

as above for me too

its really not a massive job to remove the tiles in a cube and also the substrate

for the sake of an extra few hours work your job will be so much better if you remove the ply and re board

Smash the tiles around the perimeter with a hammer, (wearing good goggles and gloves.)
Then cut through the board using a saw. Saw+wrecking bar+brute force will have the wall off the studs in no time.

Then re-board using Schluter Kerdi Board. Tape the edges using Kerdi-Band and Kerdi-Col to ensure waterproof.

- That's what I would do at least.

Times when I have gone tile onto tile with larger tiles, I have always used BAL mosaic-fix. It has high polymer content so it "bites" into glazes well and it's also easy to work with with very little slip and extended working time.

Ply can only hold 25kg of weight per sqr mtr and seen as some tiles are already on and you want to use more on top, then it will be unsafe to do so..

Do it properly and do it once..

I looked at a job recently (and I really wish I'd taken a few pics) where there was tile upon tile. Some of the tiles were so "blown" that you could rest your tea cup on the edges / lips.

I'd always strip the walls back as far as I could get them. "Perfect preparation prevents P*** poor performance".

Daz

Originally Posted by barney48

thank you- you are aptly named!
We were discussing this over dinner and I did mention taking down the wall but as my husband said he would still have to get the tiles off to get at the screws that held the ply on, now having read your post it does seem that there is no quick fix!

I'm not grumpy really, was just answering your question that's all.

Many thanks to all for sdvice, even if its not want I really wanted to hear.
And I an sure Mr Grumpy is lovely really!