18mm cement board UHF - Tile Advice

[shongu]

Hi everyone. Id need advice asap. They called me to do a travertine floor. They put 18mm cement board uhf onto a primed concrete floor with flexi adh. Some of these boards were still moving (I think not enough adhesive under), so the next day they drilled and screwed them to the concrete. We would need to put 600x600 12mm traventine on top.
The floor needs some levelling and we want to use ditra on top. Is it possible lay slc onto these boards? Also they came with plastic parts where the pipes return would the slc stick to that? Any advice would be much appreciated. I just don't want to do something isn't right.

 

[Flintstone]

What is the brand of ufh? What is the surface on the boards ? 18mm seems very thin, for a wet underfloor heating sysytem? I assume that’s what you mean

 

[shongu]

The system called warm board. It's 18mm cement board with 12mm pipes.
The surface is pretty much like hardie backer.

 

[Bill]

The system called warm board. It's 18mm cement board with 12mm pipes.
The surface is pretty much like hardie backer.

View attachment 96190

But made from gypsum......

 

[Flintstone]

Yes I’m sure they are gypsum

 

[Dumbo]

I spoke to tile master about this very same system earier this week . They said prime ,level minimum 5mm then tile.
Just as a side note , I was speaking to warm board tech also and ended up calling him . Dishonest ,deceitful and that their fitting instructions were ambiguous.
Sorry I missed out if boards are screwed down to use anticrack Matt on top of levelling .
What part of the country are you from ?

 

[shongu]

We are in London. Doing the job in Notting Hill. Plumber who put it down a bit clueless I think. I just don't want it to fail. We specified to put ditra on it. Did not say levelling but we really should.
Should we use primer G for priming as usual gypsum surfaces?
We should pour it tomorrow so in bit of a rush. Warm board does not know what goes with what.

 

[Dumbo]

We are in London. Doing the job in Notting Hill. Plumber who put it down a bit clueless I think. I just don't want it to fail. We specified to put ditra on it. Did not say levelling but we really should.
Should we use primer G for priming as usual gypsum surfaces?
We should pour it tomorrow so in bit of a rush. Warm board does not know what goes with what.

Phone tilemaster first thing. Bear in mind when priming pipe returns are non porous . Also tell them panels are screwed down .

 

[Dumbo]

The trouble with these systems is they are sold to plumbers, Builders and householders who don't understand that the tiler should of been involved from the get go to give their perspective of the job and what we require to get a quality long lasting job , ie tiler should of gone in levelled the floor prior to any panels being laid .

 

[Flintstone]

If they are gypsum then you can’t use a cement based leveller. I find when plumbers use tile adhesive to stick things down, they don’t prime, they don’t mix it or spread it right, and they probably don’t even sweep up first! Hence your loose boards

 

[shongu]

I think that is exactly what's happened.
The floor was primed but they used a 6mm plastic trowel to put it down and did not fill properly underneath. When they realized it didn't stick they started screwing the loose areas

 

[Time's Ran Out]

 

[Time's Ran Out]

Not the ideal video but it’s an apt and great song IMHO.

 

[Dumbo]

I think that is exactly what's happened.
The floor was primed but they used a 6mm plastic trowel to put it down and did not fill properly underneath. When they realized it didn't stick they started screwing the loose areas

It is designed as a floating system , and you now how we all love those .

 

[Bill]

To be fair, the last one I did with these boards, the boars were only screwed down onto 22mm ply but there have been no issues at all.

The manufacturer stated that they could be tiled straight onto with a flexible adhesive and that's what I did. I used a Norcross one too, so I think that so long as you prime them sufficiently, a quality flexi addy and you will be fine.

The correct commisioning of the heating is ultra important to the success of the tiles keeping their bond.

This is the stuff I used, over 2 years now

https://www.tileexperience.co.uk/co...s-rapid-porcelain-tile-adhesive-grey-20kg.png

But with stone, you will need to use crack mat.