UFH / Anti crack matting or liquid fibre flow floor?

[Pen]

Hi - we're renovating a house in Norfolk at the mo. I am getting conflicting advice from the stone supplier and our builder about what should be under the 22mm limestone flagstones. There is wet underfloor heating (or rather there will be soon!).
Builder says it is sufficient to "lay a liquid fibre flow floor from Weber and coat with sealer and then use a flexible tile adhesive treat the tiled floor and then grout".
Flagstone supplier is saying we need all this "Recommended Grey S1 flexible adhesive, Anti crack matting, Mapei Sand Grout, and Fila Fob sealant 5 litre".
Builder says whole point of the liquid fibre flow floor is that it's flexible and he's laid plenty of stone on top of UFH before in this way and it's never cracked. I'm stuck in the middle and have no idea what to do tbh! we're talking 150 square metres so I have to get this right! any advice gratefully received!

 

[Dumbo]

Firstly get a tiler to do the tiling after would you get a tiler to build a wall,
Secondly you need the fila sealer for the stone no matter what but I would use lithofin or universeal .
Also for limestone on a heated screed I would use a decoupling mat but would use dural ci or Schluter ditra . Go on their websites or phone and speak to their technical to explain why you should do it .

 

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[J Sid]

The stone supplier is correct, as you expect.
Hope your builder put expansion joints in the right places. You really need to talking to your Tiler as it will be him who will be doing it I hope

 

[Old Mod]

Not sure why you would take the word of your contractor over your stone supplier!
The stone supplier, and everyone above is correct.
A decoupling matting, or at the very least an anti fracture matting is required for a heated screed covered by a limestone.
As Julian mentioned above, expansion joints will be pivotal in a successful install with heated stone floors.
Don’t cut corners, with 150m2 at stake, one careless mistake will end in tears.
Also make sure your screed is 100% ready to be tiled also.
This means moisture tests and under floor heating fully commissioned before your install.
Good luck.

 

[Pen]

Thanks for your responses. The obvious answer to the question why is the stone supplier pushing the anti crack matting is that he is selling it to me! anyway I have taken into account all of your replies and will have another discussion with the builder and the tiler. Thank you.

 

[J Sid]

He is pushing the mat because it's needed, if you want to purchase it from him or elsewhere then that's choice

 

[Dumbo]

You're very sceptical about your stone supplier, you've had three answers from tilers that verify the fact that you're supplier is selling you matting, we fit tiles all day every day as our proffession

 

[Pen]

He is pushing the mat because it's needed, if you want to purchase it from him or elsewhere then that's choice

yes of course I have a choice. I asked on here because I have been given conflicting advice, so wanted some independent advice, from qualified people, who are not being biased by money. So thanks again, we are going to use the matting.
[automerge]1579170800[/automerge]

You're very sceptical about your stone supplier, you've had three answers from tilers that verify the fact that you're supplier is selling you matting, we fit tiles all day every day as our proffession

see reply above.

 

[Dave]

Just to add , Fila sealers are fine as well.
make sure the stone is dry before sealing and breathable.