Tiling on Wet/Piped UFH overlay system

[Ren+]

Hi all. Can I ask for a bit of advice please.

I’m busy quoting on a bathroom refurb that is in an established older house. I need to install a wet/piped UFH system which will be overlaid on top of the existing floor planks. Final floor will be approx 450x450 porc tiles. They’ve had another en-suite done in a similar manner, which they’re chuffed with.

The spec’s of my job are:
Existing floor is planked and is on the first floor with household rooms below. The overlay UFH system is made by Uponor and is constructed of 13mm WBP 175mm wide boards with heat reflective foil underneath (also act as spreaders I assume). The pipes are 12mm and are laid in pre grooved channels in the WBP board. It’s basically a kit system. This then needs to be overlaid with some sort of board. Just a quick mention that the UFH 13mm boards, which will house the pipes, will be screwed at 150mm centres.
This is the part where I need some advice pls. Normally I would have gone for backer board on top of wood, however the pipes will then end up under backer board … not good. As I’m concerned that the 13mm UFH overlay boards are too ‘cut up’ and not enough sheeting effect, I’m thinking of further overlaying with something like 9mm WBP ply screwed at 150mm centres and then addy to go for = Keraquick + admix. Grout = flexible FTG.

Just thought I’d mention at this point that electrical UFH and lifting the existing planks to install heating pipes underneath is not an option as customer is not keen on either.

Your words of wisdom will be much appreciated.

Thx.
Andre’

[Uheat]

Sorry Andre, Wet systems are not my area. I am sure guys will have some advice though

[Sir Ramic]

I did a similar type floor last year but the boards that held the pipe work work made of a substance similar to backker board but much thicker. I think it was made by PolyPipe.
After the fitters had laid the system a SLC was floated over it and then i used Dural Ci uncoupling membrane over that.

[Dave]

That's some hieght you will raising the floor by, can this system not be laid directly to the joist structure..?

[Dave]

Right.. i have looked into this system and i think you should consider an uncoupling membrane for tiling onto this product......you tile directly onto the product itself with no additional overlaying....

Here is some installation instructions...

Polypipe Underfloor Heating Floating Floor

[Ren+]

Hi guys

Thx 4 your input. Right first to respond to Sir Ramic. I've looked into the Polypipe product. The whole house has been replumbed with a super new pressurised continuous loop system (s-plan for all different circuits) so I thought I'd have a chat with the guys who did the replumb and they recon that they'd go for the Uponor system everytime. So that has basically set he mark and I'll have to work around it's parameters. As far as SLC is concerned, the only product I have got to trust so far is something made by Bostik called FA600. It has a reinforcing microfibre added to the dry powder which is just mixed with water (polymers in dry mix). If there are better products then it's just my ignorance. I'm a bit scared of just going straight onto the 13mm system which, as I mentioned, has been cut up quite a bit so the pipes can be set into it(does that make sense?) and I would have thought that it therefore is not very stable.

Dave, thx for looking into it. Same point as I mentioned to Sir Ramic, ... will going straight onto the system be sufficient substructure strength to resist flexing?? You recommend even going straight onto joists (removing planks ??) Hmmm ... let's put it this way, the ply boards that the pipes are laid into, are only 13mm thick and every 170mm there's a 12mm groove cut into them to fit the underlay pipes into, which means that the boards are only 1mm thick in places. I'd much rather have some support under them. I have no experience with uncoupling membrane, so your guidance in this regard will be good. I've always overlaid timber floors with at least 9mm WBP ply (screwed 150mm centres) and used an Ultimate Flex adhesive (Granfix). Hence never used uncoupling membrane. A I said, any guidance with uncoupling membrane will be well received. I understand that you're also addressing the height issue ... height is also a concern.

[Dave]

Hi ren+.. i mentioned the fixing to joists after ilooked into the product, so dis-regard that advice...

As for tiling straight onto that product , it is not something i have come across...i suggest you contact your adhesive supplier and seek tech support..

I think an S2 adhesive would be OK but please confirm this first.

[Ren+]

Thx Dave. Will give the manufacturer a buzz. Only thing is their recommendation is always belt and braces, i.e. will say use at least 15mm ply when we all know the height gain problems that causes. Was just hoping that by some luck someone had previously done something silmilar.

[Dave]

BUT the prodcut you are using is a 15mm overlay as specified....but not sure on it's stability..

[thegwads]

to ren+ - i am at exactly the same position this week. uponor wet system upstairs, identical!!!
it is solid as a rock, and been overlaid with 6mm ply, am contacting their tech guys tomorrow, but what did you end up doing? i see this is a year or so old this thread, so would love to hear how you went a bout it....
will pm you too
cheers

[faithhealer]

to ren+ - i am at exactly the same position this week. uponor wet system upstairs, identical!!!
it is solid as a rock, and been overlaid with 6mm ply, am contacting their tech guys tomorrow, but what did you end up doing? i see this is a year or so old this thread, so would love to hear how you went a bout it....
will pm you too
cheers

afraid Ren hasn't been on for over a year either

[thegwads]

have pm'd in the hope his email still works...
any other info from guys would be great

[Sir Ramic]

You will be taking a big risk tiling onto 6mm ply. 1, because of the water from the adhesive warping the ply and 2 from the heat from the pipes adding movement expansion and contraction to the ply.

[Sir Ramic]

I would be more inclined to tile diirect to the polyplumb surface than 6mm ply.

[aph257]

6mm Ply