Uneven bathroom floor prior to fitting wetroom

[JimboJet]

I will shortly be fitting out a wetroom in my ensuite. The room is small, about 2m x 2m and unfortunately has a very pronounced sloping floor. Its a first floor flat, wooden floorboards on sizable joists.

I'm pondering using the existing slope as a basis for the shower drainage - the fall is about 20mm / metre and slopes down towards the proposed shower location.

Now I'm unsure how best to proceed. Clearly getting the flooring levels correct is paramount to getting a successfully tanked and drained wetroom, but unsure of the best course of action.

I have a couple of ideas:

1. Apply multiple levels of 6mm or less ply as required to get a "stepped" level floor. Then apply a self levelling compound before finally applying yet another final layer of ply uniformly over the entire floor area. This should result in a level floor to which I can sink a pre formed shower deck. Tank as required etc

2. Remove all floorboards and apply wedges to the joists as required before adding 18mm ply. Cutout and fit preformed shower tray. Tank as required etc

3. Cut trapeziod ply pieces as required to form the elements of a custom shower tray. Apply a 6mm ply layer directly to the existing floorboards. Onto this ply, add some screed as required to form the levels and falls required then place trapeziod ply pieces as required to form the elements of a custom shower tray supported in parts by the "concrete" sandwich. Tank as required etc.

4. Apply a 12 or 18mm ply layer directly on top of the existing floorboards, using the existing falls which it appears just happen to be right for a wide floor drainage channel which I have seen available. This would be fitted against the wall side in the wetroom. Tank etc as necessary.

5. A.N.Other

How would you do it?

PS when I say ply I mean the WPB stuff.

 

[JimboJet]

Think I may have a better solution than all the above.

I will pull up all the floorboards, find some 6x2 or similar and bolt/screw these to the existing joists ensuring everything is level.

Once that is done, I'll brace these "new" joists at 90degrees to the same levels effectively forming a grid to provide extra support for the new Ply floor.

Then lay down 18mm WBP ply throughout leaving the appropriate aperture for a purpose built shower deck. Screw and countersink at 150mm centres. Caulk inbetween Ply boards. Coat with feathering compound to smooth everything over.

The rest is per standard wetroom practices... install shower drain, laydown shower deck, tank, etc etc.


1. Am I on the right track?
2. Anything I've not thought about?
3. Should I worry about any expansion gaps for the ply floor?

 

[mattysupra]

cant see a problem

 

[JimboJet]

Would I be able to get away with 12mm ply or is that too thin? I'd have marmox or wedi thermal boards on top (10mm) then the 3.5mm heating element then finally the grout and tile icing layer

 

[mattysupra]

thicker than 12mm. All depends on joist spacing tho.