Looking for advice on slate floor on anhydrite screed.

[Playwrightpete]

Please could someone tell me if I am doing this in the correct manner.
The screed was laid mid may 2016, I have just removed the laitance layer with a STR 701 floor preparation machine and now have a lovely white floor.
I plan to seal the screed with primer G, with a single coat of 1 to 1 and use but anhyfix adhesive to fix the slate tiles. But manufacturer of primer G recommends two coats. So you could use a cementitious adhesive to fix tiles , without a slip mat.
Is it best to commission the under floor heating before laying the tiles ? and also what is the best tile sealer LTP MPG or MP90 ?
Any advice would be appreciated. Thank you.

 

[One Day]

My method - Don't trust the fact that it was May - take readings with a hygrometer box/es.
Vac the floor properly, and seal using BAL SBR at 4:1 - this simply reduces water absorbtion from the adhesive and the last of the dust.
Fix using Anhyfix as usual.
(for extra safety I'd always recommend Ditra)
If you plan on using a cement based adhesive - I would definitely use Ditra.

Sealer - I use Universeal products - I can't comment on LTP sorry!

And it's 100% essential to commission the ufh - especially if you aren't using Ditra.

 

[peteablard]

If I was using a cement based adhesive I'd use the primer the adhesive manufacturer recommends. I've used Weber on anhydrite before and primed with PR360. Mixed 4:1 it takes about 6 coats before it won't take any more. If using anhyfix I'd prime with Tilemaster prume plus. As stated above the heating must be commissioned and moisture readings must be taken. If you use a gypsum based adhesive you'll be able to tile with a slightly hight moisture reading, 85% rh V 75% rh with cement based

 

[Lithofin BOB]

Sealers, Both good products , mp90 is fila

Other professional products are avalible!!

 

[Ajax123]

Please could someone tell me if I am doing this in the correct manner.
The screed was laid mid may 2016, I have just removed the laitance layer with a STR 701 floor preparation machine and now have a lovely white floor.
I plan to seal the screed with primer G, with a single coat of 1 to 1 and use but anhyfix adhesive to fix the slate tiles. But manufacturer of primer G recommends two coats. So you could use a cementitious adhesive to fix tiles , without a slip mat.
Is it best to commission the under floor heating before laying the tiles ? and also what is the best tile sealer LTP MPG or MP90 ?
Any advice would be appreciated. Thank you.

no no no and again no

don't use cement based adhesive to stick directly. As it is natural stone you should uncouple as a requirement of the british standard. Your use of anhyfix is fine but you would be better to use their primer as well in my opinion... tilemaster . If you do decide to use a cement based adhesive then I would avoid Primer G like the plague on anhydrite. Use a water dispersible epoxy primer instead.

My advice would be

prime with tilemaster acrylic primer. then stick down uncoupling mat with anhyfix, then tile using whatever cement based adhesive you like.

 

[widler]

I'd just go the whole hog and use tilemaster primer, tilemaster matting stuck with anylfix and tile with rapid or standard s1 setaflex

 

[hmtiling]

no no no and again no

don't use cement based adhesive to stick directly. As it is natural stone you should uncouple as a requirement of the british standard. Your use of anhyfix is fine but you would be better to use their primer as well in my opinion... tilemaster . If you do decide to use a cement based adhesive then I would avoid Primer G like the plague on anhydrite. Use a water dispersible epoxy primer instead.

My advice would be

prime with tilemaster acrylic primer. then stick down uncoupling mat with anhyfix, then tile using whatever cement based adhesive you like.

I don't think you're right on the British Standards Alan. I've had a good look through and found nothing to say it's a requirement for heated screed with stone. Also, I've had discussions with Schluter and Dural, who couldn't confirm that is the case either.
Stand to be corrected though.

 

[hmtiling]

I don't think you're right on the British Standards Alan. I've had a good look through and found nothing to say it's a requirement for heated screed with stone. Also, I've had discussions with Schluter and Dural, who couldn't confirm that is the case either.
Stand to be corrected though.

That being said I'd agree it's best practice

 

[peteablard]

I think it is British Standard, I'm sure someone copy and pasted it on here once. I also may have dreamt it so stand to be corrected too!!

 

[One Day]

It's a recommendation by the British stone federation. It may be in the latest bs5385, but it's not in my copy (2009)

 

[hmtiling]

It's a recommendation by the British stone federation. It may be in the latest bs5385, but it's not in my copy (2009)

I know the stone federation do. But pretty sure it's not BS

 

[Bill]

So all this talk of recommendations actually means diddly squat?

 

[peteablard]

So all this talk of recommendations actually means diddly squat?

So you wouldn't recommend decoupling then?

 

[Bill]

So you wouldn't recommend decoupling then?

I am just wondering what happened to all the lovely stone floors I have laid without decoupling? Don't recall having any problems. I know there is nothing wrong with using one but sometimes there is no need so long as you use the correct adhesives.

 

[hmtiling]

I would STRONGLY recommend using one with a heated gypsum screed as in my experience they crack more often than they don't. With regard to screeds in general then it comes down to how well they been put down and unless I've done something myself I can't vouch for that and will use a decoupler when heated and stone.