Backer Board Installation Advice with a Raised Shower Tray Former

[DazJWood]

All,

I am looking for some advice.

When I updated my bathroom eight or so years ago I used Hardie Backer boards on the wall all the way down to the floor. I then built a raised wooden structure and installed a stone resin shower tray on top. I filled the small gap where the tray met the hardie back board wall with silicon, then installed homelux matting, overlapping onto the shower tray, tiled with travertine and then sealed with silicon. It has proved to be fully water tight.

I am now currently in the process of renovating my girlfriend's bathroom.
I will be installing a shower tray former on a raised platform and tiling over this former. My question is around the type of backer board to use for the walls. I could use a similar method as before; using hardie backer board and homelux matting. However, the alternative XPF boards such as Jacko, marmox, etc... are now more cost effective and offer waterproofing also. I am a little confused though at what approach you would use when a raised shower tray former is used. If I installed the XPF to the floor and then installed a raised structure with former on top then how would I robustly seal the former to the wall? The waterproof part of the boards are under the top cementitious layer. Surely water would soak into the top layer and travel down past any silicon or waterproofing tape. Is it better to install the shower former to the existing wall first and then install the backer boards on to the wall so they sit on the top of the former. Therefore, any water would run down on the the former.

Any advice would be greatly received!

Many thanks,

Daz

 

[Waluigi]

Excellent question, Daz. I have thought about this before and it definitely shows a slight weakness in the concept of cement faced foam Tile Backer boards although I think the risk is minimal.

Even if you were to apply some tanking membrane say a foot up from your tray and overlap your tray, moisture could still potentially get below the tray via the cement face. Very unlikely IMO.

As I said- every system has a weakness. Almost all. The Homelux system you mentioned has a weakness at the joints and overlaps as Homelux recommend a tile adhesive for the joints which is porous.

If you want a fail safe board to use in your shower then I believe there is only one without a weakness and that’s Schlüter Kerdi Board.

That said, I wouldn’t hesitate using an XPS board when creating a shower with tray and simply applying a bead of silicone between the tray and the board as I find this acceptable. That’s just me though. I also wouldn’t hesitate using tanked plasterboard.

 

[DazJWood]

Thanks for the advice thus far.

Just to throw some more factors into the mix... The walls are either back to brick or block. Brick wall is fairly level but not fully plumb but the block work is fairly uneven. Any advice on which backer boards would be good for a masonry wall? Again there seems to be lots of options and lots of different methods for fixing; from using stick adhesives, dot and dab, mechanical. Obviously I would follow the Manufacturer's Instructions for the type of board I use but ideally looking for any recommendations based on experience of use. My concern is ensuring whichever board I use can be installed level and it will take the weight of the tiles (Porcelain tiles will be used).

Thanks!

Daz

 

[Jordanlinc]

Bump