Tiling in a ply lined shower enclosure

[Thepenetrator1]

Hi, I tiled my bathroom 3yrs ago and where there are stud walls I used wbp ply to line the walls then sealed with a Pva bond and tiled on to it. My shower cubicle falls in the corner of the two stud walls and up until now has been fine. The other day I noticed the grout on one of the tiles at the bottom was falling out so I took the cubicle off and pulled away the tile. It seems that water has been seeping in around the 3mm silicon bead along the bottom and over time being absorbed into the ply (see photo). I was going to dry this out. Re bond / re tile and re seal .I'm not sure if there's any waterproof paint I could apply first or should I use a plastic seal where the tiles meet the shower tray as id rather this not happen again. I could pull off the ply and use aqua board but I feel it would be a massive job as its tiled floor to ceiling all round so id be pulling away a lot of tiles to get to the joints in the sheets and I'm not sure if the ply is 12mm or 9mm I know aqua board is 12.5 mm at wickes. Any one have any suggestions / ideas. Thanks

 

[iwaters]

A tiled shower cubicle with plywood walls and bonded with PVA

I can't believe it lasted 3 years.

WBP ply isn't water proof, it just wont delaminate when it gets wet, but it will absorb water. PVA is a terrible idea in bathrooms, water re-activates it and it softens. Either water is getting in between the shower tray and wall and is being wicked up the ply or via the grout joints

The only way is to rip it out and use a concrete backer board and re tile. You may be able to bodge the tiles back on as they come away but it will be just that. Depends whether you want to spend the time and money