Laying york slabs on cemfloor

[Rugrat]

Hi, Im planning to lay a reclaimed york stone floor on a cemfloor screed with a wet ufh system. The stones are 40 to 60mm with most being about 50mm. What would you recommend laying the slabs on and will I need to do anything to the screed prior to laying? Thanks for your help

 

[Dan]

Make sure you find the lowest point of the floor, and use the thicker tiles there. And as you come to the higher part of the floor, use the thinner ones.

Tiles that change thickness from one end to the other need some thought. Those often when laid flat are actually a parallelogram shape and you can't always get them square so watch out for that.

Haven't got a clue about the screed. I'm not actually a tiler.

How long has it been down?
Do you have underfloor heating in it?
Anddddd I think those are the two main questions the lads will need answers to to answer your question lol



Most have logged off it seems to this will be something answered tomorrow.

I assume if it's flat and nice to go on and not crumbly or anything, you'll tile direct to it with some good cement based adhesive that has additive already in so it sticks to the low absorption rate of the tile.

Other than that you'll have them down by Wednesday? 😁😆😂😀

 

[Old Mod]

Hi and welcome to the forum Rugrat 😊

Cemfloor being a liquid screed will more than likely have layer of laitence on top, this must be removed.
This can normally done with a floor scrubber with a 60# copper disc.
It presents as a scum on top of the screed, although a lot of screed companies now claim that their liquid screeds are either low or no laitence finish.
It’s a very dusty job without correct dust extraction equipment, ensure area is well ventilated and masks are worn.
Although most hired sanding equipment is supplied with dust extraction equipment, check before hand.
Vacuum and prime post sanding.

This is a cemfloor, two images, one before and after sanding.

Make sure the ufh has been commissioned correctly first. (Taken thro heating cycle)
Being a natural stone a antifracture mat or decoupling membrane would normally be advised on top of the screed.
Once installed, the heating cycle should be repeated 28 days after install prior to normal use.
It takes 28 days for the adhesive to cure.
This will help prevent thermal shock.

This is quite a challenge for a DIY tiler, good luck.

 

[Rugrat]

Thanks for the replys.
The floor has been down for 12 months and the ufh commissioned.

As always, more questions;

I saw on this forum a discussion about cemfloor New Cemfloor Liquid Screed - https://www.tilersforums.com/threads/new-cemfloor-liquid-screed.84495/
and the need or not to sand/prime. The last post on that thread said that 'he' didn't sand the floor. Please can you confirm what the thinking is now on this, and if anyone has had a failure.

If im using a decoupling membrane why does the floor need sanding?
Which decoupling membrane is best value?
With the variable depth of the stones it will need a lot of adhesive, again which would be best value? Can a cement/sand (plus something??) mixture be used to lay them on?

 

[Tmk Tiling]

What type of sanders do you use and where do you get the copper discs from
Thanks

 

[Glynn]

Tilemaster have produced this specification for Cemfloor.

 

[Ajax123]

Cemfloor as with ALL screeds should be subjected to mechanical preparation in order to remove surface contamination, laitance, mud, plaster etc etc. In the case of cemfloor particularly it has a spray in curing agent applied on installatio this helps prevent plastic shrinkage cracking. It is not physically a part of the screed and should be removed. If this has been done already that's great but if not then light sanding is wholly appropriate.