Large format tiles on liquid screed

[linearpancakes1]

Hi folks,

We're having our downstairs tiles installed soon, about 82m2 of 1.2x1.2m square porcelain tiles onto an anhydrite liquid screed, with UFH.

We've had reasonable quotes from two tilers, but they looking to do things a little differently, and we're not sure on the best approach. Both are looking to use Durabase matting.

• Priming / under matting adhesive. One is looking to use 2x layers of primer and a cement based adhesive. The other is looking to use a single layer of primer and Anhyfix. I suspect both options are fine, but opinions welcome.
• Expansion joints. We don't have any in the screed itself, as we understand it's fine not to with this type of screed. It has dried nicely without any cracking, after UFH on too. One is suggesting to line up tile joints with doorways and have colour matched Silicon joints, and really stated the importance of this to avoid cracking. The other said there's no need due to the decoupling matting. This one I'm not really sure on.
• Grout. One is suggesting using epoxy grout, the other regular. From what I can see, the epoxy grout, if colour matched, looks like a good option for durability, at a little higher cost.

Thanks for any insight you might be able to give!

 

[Anthony]

Go with the guy who will prime twice,and cement adhesive.
You can’t fix matting with a gypsum based cement.and it has a poor grab on the tile,compared to cement based adhesive,And your never going to get a 1200x1200 around door ways without cutting them in the door rebate. Hope this helps

 

[Ajax123]

Anhyfix is no longer available

 

[linearpancakes1]

Thanks guys. Would you recommend expansion joints at doorways if we're using decoupling matting already? I'm guessing this would still be best practise, though in practise it "should" be fine without.

And if so, would 3mm Silicon joints do it, or should we be looking at making them 5mm? I've attached an image to be more specific. Thanks!

 

[Anthony]

Thanks guys. Would you recommend expansion joints at doorways if we're using decoupling matting already? I'm guessing this would still be best practise, though in practise it "should" be fine without.

And if so, would 3mm Silicon joints do it, or should we be looking at making them 5mm? I've attached an image to be more specific. Thanks!

View attachment 127745

I always cut in the doorways even with the matting, as it’s usually the weakest part of the floor and it’s not
Always possible to get a tile around a door way (depending how it falls at the door way) especially a 1.2x1.2. 3mm joint is plenty. I would use matting with that size. The bigger the tile,the weaker they are!