Wetroom floor buildup

[Workerbee]

Hello - I was wondering if you'd be able to sense-check my floating floor plan, please? 

 

The wetroom is just a corner of the bedroom, about 3.7sqm. In the bedroom, I'll be putting 50mm PIR on the slab, topped with 22mm chipboard. For the wetroom floor, I therefore thought I'd do the same, then topped with impey waterguard, electric ufh, and natural stone.

 

To help with stability on the floating floor, I thought I could add a perimeter of battens like in the picture below, and screw the chipboard into it: 

 

Does this sound like a plan?

 

Thank you.

[Nestor]

Floating so battens not fixed to the slab?

 

Edited yesterday at 17:22 by Nestor

[Nickfromwales]

You're either floating or not. Fixing the chipboard to the battens would cause a conflict.

 

Why floating? Seems added uncertainty with a mixture of bedroom > bathroom wetroom flooring.

[Nestor]

11 minutes ago, Nickfromwales said:

You're either floating or not. Fixing the chipboard to the battens would cause a conflict.

 

Why floating? Seems added uncertainty with a mixture of bedroom > bathroom wetroom flooring.

What Nick said,

A tiled floating floor wet room does not work for me, I would want it all fixed with zero movement.

When I tiled our wet room I fixed Hardie backer board through to the P5 Caberdek which is fixed to the floor joists.

Edited yesterday at 17:59 by Nestor

[Workerbee]

Thank you both. It's a renovation that previously had 50mm polystyrene on the slab, topped with 22mm chipboard, so I don't feel I have much choice about it being floating. My thinking was that the battens would provide more stability for tiling. I would screw the battens to the slab, then screw the chipboard to the battens.

 

I'd originally thought about XPS tile backer boards adhesively stuck to the slab, but manufacturers seemed to think tongue and groove was essential. 

 

Would there be a better way, do you think?

[Nickfromwales]

14 minutes ago, Workerbee said:

Thank you both. It's a renovation that previously had 50mm polystyrene on the slab, topped with 22mm chipboard, so I don't feel I have much choice about it being floating. My thinking was that the battens would provide more stability for tiling. I would screw the battens to the slab, then screw the chipboard to the battens.

 

I'd originally thought about XPS tile backer boards adhesively stuck to the slab, but manufacturers seemed to think tongue and groove was essential. 

 

Would there be a better way, do you think?

Yes. Stop listening to the manufacturers and go with the bonded XPS (Wedi / Jackoboard) type material. 
 

You’ll need to self level over them as they follow to subfloor, but that’s your opportunity to bury the electric UFH. 👍

 

Then tank and tile. 

[Workerbee]

Thank you for your help with this. My two worries about that would be the low amount of insulation for the electric ufh (xps a worse insulator and the self levelling eating into an already shallow buildup), and that when the ufh breaks, I'd need to cut into the tanking and self levelling, not just the tiles.

 

Would the chipboard idea (either with battens, or without and bonded to the slab) definitely not work? I'd also looked at gypdeck 18, but it's expensive and presumably wouldn't connect into the 22mm bedroom chipboard.

[Nestor]

Some random thoughts, not a professional but built a house with 4 bathrooms.

A  level threshold to the bedroom would be very critical for me, within a few mm.

 

I fitted wet UFH in foiled EPS boards under the 6mm Hardie Backer and electric cable in a 50mm sand & cement screed.

 

You could use 18mm P5 or 12mm Hardie Backer above the insulation and slab but would need to be fixed well, no movement.

 

I think fixed battens to the slab would work.

 

Electric, (is it self adhesive matting) fitted to one of the above then apply thin layer of self levelling to encapsulate heating elements.

Then tank and tile.

 

What the Boss @Nickfromwales said.

 

 

 

[Workerbee]

Thank you @Nestor - that's great. Really appreciate your and @Nickfromwalesinput, as I've been going around in circles!

 

13 hours ago, Nestor said:

A  level threshold to the bedroom would be very critical for me, within a few mm.

That's interesting - I'd aimed for about 10-15mm difference and add a threshold strip, but perhaps I should aim for less. 

 

If so, would 10mm insulated tile backer board work, screwed to battens? It would lower the height and at least add a little more insulation, although the screws would be thermal bridges. Or gypdeck 18, which is t&g.

 

I'm not sure which electric ufh - yet another thing I need to research, so I'm open to recommendations! 

[Nestor]

I used the In screed cable from here, have a read around.

https://flexel.co.uk/product-category/underfloor-heating/

 

Just check the UFH matting adheres to the board, the self levelling will help bond it all together.

 

Regarding threshold heights, on a new self build it can become a bit obsessive. Just do your best with the materials available.

 

Do another section drawing in mm with the new materials for your own peace of mind including tile and the adhesive.

 

Make a start, hopefully using large format tiles!  

I had over 1100 hexagonal and small rectangonal tiles to fit in our Wetroom. Never again.

 

I used https://www.protilertools.co.uk as well.

 

 

 

 

 

Edited 6 hours ago by Nestor

[garrymartin]

Personally, I'd scrap the PIR and Impey Waterguard and put 60mm Marmox straight to the slab with tile adhesive (possibly another 10mm on top at 90-degree depending on existing floor height). Stick the UFH mat on top of that. A couple of conduits with temperature sensors in them (one for backup).Self-levelling compound over it (fibre reinforced). Tile on top of that. You'll probably end up very close to the height of your other flooring, and it will be a very straightforward buildup.

Edited 6 hours ago by garrymartin

[Nickfromwales]

2 hours ago, garrymartin said:

Personally, I'd scrap the PIR and Impey Waterguard and put 60mm Marmox straight to the slab with tile adhesive (possibly another 10mm on top at 90-degree depending on existing floor height). Stick the UFH mat on top of that. A couple of conduits with temperature sensors in them (one for backup).Self-levelling compound over it (fibre reinforced). Tile on top of that. You'll probably end up very close to the height of your other flooring, and it will be a very straightforward buildup.

Another for the KISS approach   

[Nickfromwales]

3 hours ago, Nestor said:

I had over 1100 hexagonal and small rectangonal tiles to fit in our Wetroom. Never again.

lol. 
 

I suggested similar to a client once, when younger and even dumber, with glass mosaics.

 

It was a never-ending punishment to lay, and then the grout just refused to dry as I’d made it a bit wetter than usual (to give me some more open time)……

 

Then, whilst stood in the bath grouting and buffing like it was my last day on earth, I bent over and head butted one of the sharp copper pipes I left for the shower (with no cap end) and still have the Harry Potter scar on the top of my forehead; I am now ever-reminded of that “fantastic idea” I once had.

 

ffs. 🤦‍♂️. 
 

Long live the large format tile!

[Nickfromwales]

6 hours ago, Workerbee said:

If so, would 10mm insulated tile backer board work, screwed to battens? It would lower the height and at least add a little more insulation, although the screws would be thermal bridges. Or gypdeck 18, which is t&g.

 

I'm not sure which electric ufh - yet another thing I need to research, so I'm open to recommendations! 

 

22 hours ago, Workerbee said:

Thank you for your help with this. My two worries about that would be the low amount of insulation for the electric ufh (xps a worse insulator and the self levelling eating into an already shallow buildup), and that when the ufh breaks, I'd need to cut into the tanking and self levelling, not just the tiles.

 

Would the chipboard idea (either with battens, or without and bonded to the slab) definitely not work? I'd also looked at gypdeck 18, but it's expensive and presumably wouldn't connect into the 22mm bedroom chipboard.

A solid section of XPS board, and zero battens.
 

The talk of battens has left the building, and is not coming back, which is my lame attempt at a subliminal message.

 

To reiterate. Battens = 🤐

 

You can have this floor 10-20mm higher to get more insulation in, that’s a good idea all round. A decent chamfered timber (hardwood) threshold has been great a way out of many similar transitions that I have done over the years. Works a treat.

 

UFH over the XPS tile backer boards (no place for Hardie type boards here sorry) and then the least amount of SLC as possible, then the flooring.

 

For stone, you can just lay on a decent bed of flexible tile adhesive immediately over the SLC.

 

Or, if you’re brave or are paying a tiler, they may be ok to simply lay the tiles straight over the UFH wire / mat and save you having to use the SLC at all.

 

That’s down to how much undulation there is in the subfloor as this will be represented above the XPSc as that will be bonded down, again with flexible tile adhesive.
 

You can use that first layer of adhesive to remove any undulation, which may be another way of reducing layers; you can then do away with the SLC if the prep is good as above.