Mosaics over electric UFH & chipboard? - Tile Advice

[Ben R]

Hi all

Installing an Impey wetroom former/tray & tanking kit. The floor will be tanked, then electric UFH, then mosaics... but before that, the existing subfloor is P5 grade chipboard which is in good condition. I assume I'll need something over the top of that before tanking, i.e. thin ply/tile backerboard/decoupling membrane. If so, which is preferable with tanking + electric UFH? Or am I better to take up all the chipboard flooring & start again with thick ply?

Secondly, what's the best way to get a nice flat surface after laying the electric UFH (4mm) - ready for the mosaics? Can I just use level it off using floor tile adhesive, then come back the following day & lay the mosaics?

Thanks in advance

 

[Old Mod]

Hi and welcome to the forum Ben.
How are you connected to this job may I ask?
Installer, client, pro, or diy?

 

[Ben R]

Hi and welcome to the forum Ben.
How are you connected to this job may I ask?
Installer, client, pro, or diy?

Thanks for the welcome

I'm a plumber, with a significant portion of my work being bathroom installations. More than happy/confident with the actual tiling aspect of it all, but there seem to be more & more products available at the first-fix stage these days... when I started out, it was ply or... well, ply

I have tanked a couple of wetrooms before, but it was years ago, so can't remember what timber the subfloor was underneath - and from memory, it was just an off the shelf kit like Homelux & definitely no electric UFH.

 

[Old Mod]

You'll never get a satisfactory finish over UFH with adhesive unless you're very well practised.
Personally I'd overboard with insulation boards, glued (tile adhesive) and screwed with wedi washers.
Then install the UFH and latex over the top to give a satisfactory surface for tiling, then tank over the slc before tiling with mosaic. That way you'll have a watertight installation and your UFH protected.
The same as this.

 

[One Day]

What he said ^

 

[Ben R]

You'll never get a satisfactory finish over UFH with adhesive unless you're very well practised.
Personally I'd overboard with insulation boards, glued (tile adhesive) and screwed with wedi washers.
Then install the UFH and latex over the top to give a satisfactory surface for tiling, then tank over the slc before tiling with mosaic. That way you'll have a watertight installation and your UFH protected.
The same as this.
View attachment 88560 View attachment 88561

Many thanks for taking the time to reply. Looks like I've got some research to do! A few questions if I may:

• When you say insulation boards, is that something I can just buy off the shelf at Topps or Tile Giant? Or if I need to purchase online, any recommendations?
• I assume latex & slc are the same thing? I've never used it before & just wondered how easy it is to work with?
• Finally, is it definitely okay to tank over the UFH? I only ask, as the Impey website has those two the other way round-?

Great looking floor by the way

 

[Old Mod]

Thanks,
You wouldn't be tanking over the UFH exactly, you'd have SLC/latex (same thing yes) in between.
How do Impey suggest you cover the UFH, with adhesive?
That'd be mad imo, mainly because you will not achieve an acceptable finish floor that way, it'd be like the Rocky Mountains!
Insulation boards/tile backer boards, the same thing. This doesn't include cement boards like hardie or aqua board. The cement faces/backed boards with exruded polystyrene in between. Dukka board or wedi board type. Secured firstly with tile adhesive, then with screws and wedi type washers maximum 300 centres.


Using slc is another post haha

 

[Uheat - Jake]

UFH Mat will need a SLC over the top and then the Tanking kit on top of the SLC, it's the way we recommed for our products.

We can supply Tile Backerboards, UFH, SLC and Tanking kits, take a look on www.uheat.co.uk

 

[Ben R]

Thanks,
You wouldn't be tanking over the UFH exactly, you'd have SLC/latex (same thing yes) in between.
How do Impey suggest you cover the UFH, with adhesive?
That'd be mad imo, mainly because you will not achieve an acceptable finish floor that way, it'd be like the Rocky Mountains!
Insulation boards/tile backer boards, the same thing. This doesn't include cement boards like hardie or aqua board. The cement faces/backed boards with exruded polystyrene in between. Dukka board or wedi board type. Secured firstly with tile adhesive, then with screws and wedi type washers maximum 300 centres.
View attachment 88779

Using slc is another post haha

Impey suggested tanking, UFH, SLC, then mosaics.

Wedi washers look good When you say maximum 300 centres - presumably you mean no further than 300mm apart, i.e. 200 or 250mm apart would be fine too? And no specialist screws required?

I'll get searching the forums on using SLC

EDIT: Would www.toppstiles.co.uk/section41/page1/insulating-boards or www.tilegiant.co.uk/prowarm-backer-pro-6mmx600mmx1200mm.html do for insulation boards?

 

[Old Mod]

Sorry I'm commuting at the moment, I'll reply later if no one else does. But look at our sponsors link above, see what they can offer you.

 

[J Sid]

think you need to fit impey waterguard to the tray first as tile adhesive or SLC will not stick directly to the tray and to seal the gulley.
I'd fit 6m insulation boards as above then waterguard to tray over lapping the boards where they stop by the tray.
fit ufh and then SLC over these, making sure it doesn't all run down the drain with a expanding foam dam.
then tank / waterproof the hole area, floor and walls with a waterproof and uncoupling membrane https://www.isomat.gr/wp-content/uploads/2015/12/e-waterproofing.pdf

 

[SJPurdy]

I would check with board manufacturer re. number and spacing of screws/washers. 300mm centres sounds a bit excessive to me. The last data sheet I had from Wedi (it may now be out of date) stated to fix the Wedi board to the chipboard with flexible cement based adhesive (after applying an appropriate primer and letting it dry). Then when dry fix using the screw/washer system at a rate of 5 per m2 and fitted no closer than 30mm from the board edges. Washers screwed down to the surface and then lightly tapped with a rubber mallet to drive flush with the surface and then the screws retightened.

 

[Dan]

Have a word with www.uheat.co.uk you'll get a discount for being a forum member, and a very good discount if you get a trade account with them.

 

[Ben R]

think you need to fit impey waterguard to the tray first as tile adhesive or SLC will not stick directly to the tray and to seal the gulley.
I'd fit 6m insulation boards as above then waterguard to tray over lapping the boards where they stop by the tray.
fit ufh and then SLC over these, making sure it doesn't all run down the drain with a expanding foam dam.
then tank / waterproof the hole area, floor and walls with a waterproof and uncoupling membrane https://www.isomat.gr/wp-content/uploads/2015/12/e-waterproofing.pdf

Thanks. So I'd essentially be tanking/waterproofing it twice? Once with the Waterguard & again with the Isomat?

 

[Old Mod]

I would check with board manufacturer re. number and spacing of screws/washers. 300mm centres sounds a bit excessive to me. .

Could well be correct Steve, I just had Schlüters recommendation in my head when I wrote it, they recommend 250mm centres.