Shower tray beneath tile backer board

[JimmyJohnJoJr]

Evening, I've got myself in a not-so-ideal scenario.

Bathroom is 1.8m wide, I've a shower tray which measures 1.8m so it's going to go wall to wall.

I have studded the wall using small 200mm batons (I could have used dot and dab but that's where I'm at).

I'll be using tile backer board and tiling the shower area. In an ideal scenario I would put tile backer board to the floor and use classiseal between the backerboard and the sides of the tray but I can't do that here as the tray won't fit.

The tile backer board is now going to have to sit on top of the shower tray (which has a raised border/lip)... what can I do to ensure a good seal around the bottom of the shower tray?

Thanks in advance for any advice.

Image below:

 

[Madrab]

I guess these fancy seals all serve a purpose but TBH they just aren't needed.

How/what is the floor, it needs to be nice and flat, clean and level. Is the wet space to be tanked?

Usually trays are a few mm shorter than the advertised size, how is the tray planned to be fixed to the floor? I'd use silicone adhesive underneath the outside edges and plenty of spots inside the tray then a good line of good quality silicone sealant along the long back edge. Drop drop the tray down and push back against the back wall quickly before it all grabs, leaving a couple of mm either side on the short edges. Clean off the excess silicone that'll be pushed out the back and then fill the gaps on short wall sides ensuring there's no air caught, use a small screwdriver to mix the silicone and fill flat to the top of the tray with silicone, use a soft flat edge to level all the way around and leave for 24hrs to set.

That will provide the 1st primary watertight seal all the way around the tray and secure it into place. Then fit the backerboard down onto the tray, add another small bead of silicone all the way around the tray edge, that's seal 2. Once it's tiled then another silicone seal at the tray edge and that the final 3rd seal. Shouldn't ever leak with that in place, only reason it would is if there's movement in the floor/walls, so make sure everything is nice and solid before fitting.

 

[foxhole]

I would use shower panel , no need then for backer board .

 

[JimmyJohnJoJr]

Cheers @foxhole - wife has chosen tiles. We all know that that means we're going with tiles here.

Cheers too @Madrab - floor is larch laid over the joists. I honestly don't know how best to fix the tray to the floor - do you suggest a few tubes of silicone around the edges and on the base?

Just reading/looking around. I'm wondering if I could use this and instead of it going between the tile backerboard and the tiles I put it behind the tile backer board. looks like it might be a decent solution (aqualux leaksseal type product). The lip on it looks to be what might get me out of the tight spot What are your thoughts?

 

[robinbanks]

Prefer madrab's advice if I'm honest; fit tray, fit backer board and seal to tray, fit tiles and seal to tray. The end

 

[Madrab]

The lip on it looks to be what might get me out of the tight spot What are your thoughts?

Nope .... the lip on the seal is what will collect a lot of crap over time and the silicone will end up going black, cut out countless numbers of them. Don't get me wrong they can last well for a fair amount of time but eventually, like all of those wall seals, they do need to come out.

You say it's to get you out of a tight spot, what exactly is the tight spot? Would that be a significant gap to cover because something's out of square?

A larch floor, now there's a novelty, don't see many of them TBH.

As far as what to use to lay it onto the floor, if you have it enclosed on three sides then you need something that it going to level out quickly with the min of fuss. I use modern silicone polymers (adhesives, not sealant) a lot of the time to fix to the floor surface with sealant along the edges, as I find them more than suitable but that's all down to the prep IMO.

Some manufacturers ask for mortar mixes, flexi tiles adhesives etc and they need to be used to retain the warranty and I'll use a flexi tile adhesives when it comes to hard/concrete type floors, if it's not going onto a plinth.