Leaking tiled shower enclosure

[nicktee]

Thanks Gcol, I will try flexible grout then (no update here for a while as I won't being doing it until the rest of refurb).
The tray support is pretty substantial, is built up from the concrete underfloor, feels solid and the silicone does not seem to have separated from the tray or wall. The leak is at the top edge of the tray, it's not getting down the back.

 

[gcol]

What I was suggesting was. if there's any give in the tray then it might be causing the wall to flex and crack the grout.

 

[nicktee]

OK, I'll bounce up and down in there and see if I can spot anything.
The tray is stonecast and the platform is 4 x 2 (all edges supported plus 2 cross pieces) and 12mm ply, everything screwed and glued. Should be fairly solid I'd have hoped.

 

[gcol]

OK, I'll bounce up and down in there and see if I can spot anything.

Well put it this way, if you think the cracking grout is down to wall movement, something's gotta be making that wall move. So unless you've been nailing your missus against the wall in your shower then your looking at the tray. Unless there's something else of that wall.
How did you tile the corner where the 2 walls meet - did you leave a gap and silicone it or did you butt em then grout or silicone? Strange that the cracks should be on both walls.

 

[nicktee]

I left a 2mm gap and siliconed it, no grout. Most of the cracks are on one wall only. Good point, I don't know what makes the wall move.

 

[nicktee]

I apologise to anyone still monitoring this thread for not giving you the final outcome.
Having stripped the tiles and as much cement as possible from my first attempt I re-tiled using adhesive apparently specifically designed for tiling on wood and a flexible grout (powder). It made no difference, I had exactly the same problems. I was recommended to start yet again but to use a rubberised sealant to ensure the wood was waterproof and the the adhesive would take.
I couldn't stand the thought of tiling three times so I stripped the tiles and used Respotex panels glued and screwed (behind the shower frame) over the ply. No problems with leaks!
Thanks to everyone for your help.
Nick

 

[Softus]

...I've called a plumber.

What did you call him?