Waterproof tape in shower

Can any of you experts help me with this? I have Wedi board on my shower walls, I propose to tile down to the shower tray. I understand the logic behind waterproofing the Wedi board joints etc but presumably this will only ensure that the water, that ultimately may get through the grout, runs down the wall rather than into the board or wall behind. Since this will now be behind the tiles it will just run under the shower tray won't it?
Do I need to worry about this? The shower tray is mounted on ply but is not tanked. What's the worst case scenario - surely we're only talk about tiny amounts of water unless I completely screw up the grouting.

It’s normal procedure to tape/seal all board joints, weather you use a truly waterproof backer board (Wedi) or a water resistant type (Aquapanel etc). Nothing wrong with using Wedi on your shower room walls at all but I would normally only go to that in a wet room. I mainly use Aquapanel in showers/baths which is perfectly adequate & tape the joints with fibre glass plasterboard reinforcing tape (which I always have). Since you’ve gone to the expense of using a truly waterproof backer board, it seems silly not to use a waterproof tape but your decision.

It doesn’t take much moisture to cause an awful lot of damage & without the tape it can wick through the joint into whatever substrate is behind; at the very least this will turn into something very smelly. I hope you used WBP ply for the shower base?

Thanks Richard. I think WBP ply was used for the shower tray but this was done by a plumber - I'll ask him. Sorry it's taken a while to respond

jonnyiles said:

Sorry it's taken a while to respond

Click to expand...

Had to go to "brain back up drive" to retrieve info

jonnyiles said:

I think WBP ply was used for the shower tray but this was done by a plumber - I'll ask him.

Click to expand...

Not sure what you mean ; is this under the tray? please tell me your “plumber” didn’t use WBP to line the walls in the “wet” shower area