400 x 400 Tumbled Marble Tiles

[crownford]

I have bought some 55 square metres of 400 x 400 tumbled marble tiles, 50% are nero marquina and 50% are carrara white and will be laid throughout our hallway and dining room on top of wet underfloor heating which is covered (in different areas) by two different substrates, ply and cement based screed. To ensure that the rate of expansion differences between the substrates doesn't cause issues we intended to lay a dislocating membrane between the substrates and the tiles.
I provide these details for completeness but the essence of my problem is that I have had two tilers look at the job and both have different ideas as to how to approach it.
The first thinks that the dislocating membrane is unnecessary and that a good flexible adhesive will do the job well enough. He also says that the stone will require sealing with Lithofin stain stop prior to laying to prevent the grout staining or adhering to the tile face. (a real headache when you consider the amount of tiles).
The second thinks that the dislocating membrane is essential and that the tiles should be sealed with the Lithofin only prior to grouting after they are laid.(much easier of course)
Who is right? They both have good experience and both come recommended.
Many thanks in anticipation of your considered response.

 

[crownford]

I was told that it would help reduce noise in the rooms below (???)

 

[DHTiling]

How..?

If you want noise reduction then use acoustic boards...

You have had some strange advice outside of this forum..:smilewinkgrin:

 

[crownford]

In my experience the world is full of people who, despite knowing b*gger all on a b*gger all chart, are more than happy to give advice, solicited or not on any number of subjects. That's why I'm here, for good considered advice from professionals who are clearly very proud of their craft. Credit to all of you for your positive contribution.

 

[Terry Cottar]

In my experience the world is full of people who, despite knowing b*gger all on a b*gger all chart, are more than happy to give advice, solicited or not on any number of subjects. That's why I'm here, for good considered advice from professionals who are clearly very proud of their craft. Credit to all of you for your positive contribution.

IMHO for what it's worth the majority of people on here know what they are talking about and in general are speaking from experience and if they are not they have the added disadvantage of another 1000+ who do know what they are doing reading their posts as well so if the wrong advice were to be given there are plenty waiting to correct it. The advice you have been given to date is spot on. You have to decide whether or not you want to accept it.

tel

 

[crownford]

I am going to go for it without an expansion joint, ensuring that there is no deflection between the substrates, using Dural CI matting and following everyones sage advice. (apart from the "don't do it" advice which I accept is valid)
In the event that this turns out to be a mistake and an expansion joint is shown to be absolutely necessary is the remedy as simple as removing the row of cracked tiles and relaying new with the necessary expansion joint or is it more complicated than that?