Thin porcelain 6mm x 1mtr x 1mtr on under floor heated screed

[Tim kingston]

Hi all, I have a 200 sqr mtr floor to fix thin porcelain 6mm x 1 mtr x 1 mtr on under floor heated screed. I'm sure I need to use a decoupling mat, any suggestions on which one would be best to use. I would like to use the lightweight highly deformable adhesive from Mapie and levelling clips. I have fixed the large format thin tiles before in small areas, but would wellcome any advice using them in a large area on a heated screed.
Tim the tiler

 

[Chalker]

Hi .before you decide on decoupling.
Firstly identify the type of screed. Then see if it’s a type that needs the latience removing. You need to know how long the screed has been Down and the moisture content. The u derfloor will have had to be fully commissioned too.
If all is done properly and a primed accordingly I wouldn’t use decoupling. But as a belt and braces, I would use Ditra.

 

[Old Mod]

Hi and welcome to the forum Tim,
Just over 2 years for your first post, glad you took the plunge. 🙂

This is just a regular s/c heated screed yes?
Is it moisture free and fully dried?
Ufh fully commissioned?
If yes, then;
Meticulously clean it,
Prime it,
And unless the original screed is flatter than flat, latex it until it is.
You need FLAT.
You can use a 1mm anti fracture mat, no need for ditra, Tilemaster antifracture is one of the best out there.
And Mapei’s new lightweight ex large format adhesive is ok, I’ve seen it used, I’d still prefer Isomats AK22 over that tho.
Lightweights can skin quickly, just don’t get too far ahead of yourself.
And above all, you MUST ensure you have a totally solid bed beneath the tile. Can’t stress this enough.
Good luck.

 

[Old Mod]

What Paul says above is all correct, but we do have different opinions on matting, which if you surveyed 100 people, it’d be a close run race as to who’s opinion would come out on top.

Is this domestic or commercial?
If it’s commercial I wouldn’t consider Ditra.
(Sorry Paul 😀)
Reason being, Schluter will not advocate its use with materials under 6mm thick, so make sure your tiles measure a GOOD 6mm if used.
Reason I don’t use it is because the best substrate for thin tile is very very solid, ie as close to the screed as you can get it, this way it won’t flex and stress the tile.
Even with Ditra filled, it’s still not solid, an antifracture mat is. (There are waterproof ones available too)
But again it’s all down to prep. Spend an extra day flattening your screed if it needs it.
It will save you an immeasurable amount of pain haha

 

[Tim kingston]

Many thanks for your opinions chalker and 3_fall.
It's a domestic floor and not screeded yet, and will have the fibres in s/c screed.
I will make sure it's cured, flat and heating comisioned.
I like the idea of tile master anti fracture mat as it's close to the substrate and more supportive.
I will also have a look at the ISOMATS AK 22.
Thanks again for your advice.
Tim

 

[Time's Ran Out]

Good post.
Good replies.
Just got to find another 99 people who know what your talking about!