HELLO TILERS! Please hep do I need a decoupling membrane??

[MISSTEE38]

Hi everyone! Ive got on here as I am a non tiler, but we are currently about to put down 66sqm of bottcino marble flooring, we are nearing the end of a big renovation. Our builder has installed a 50mm screed over wet ufh. We put it down middle of Dec and have been using the heating as we are having to live in the building site. I have read on here that we should have had joints put in at doorways and where we have different temperature zones which they haven't done. I notice now that we do have hairline cracks on all door ways, but builder says its nothing to worry about. We are about to employ a recommended tiler from a Tile Choice shop, who has been tiling for 30yrs and he was going to lay tiles straight onto screed with a flexi adhesive. Is this going to be ok, as another tiler had asked if any of my other quotes were laying a d coup membrane, which they weren't. Now I am very worried we will have trouble if we don't put the membrane down, any advice appreciated. Thanks.

 

[Gazzer]

I would go with the membrane IMO

 

[Ian]

Welcome along to TF. As above, use a membrane when natural stone and underfloor heating are together.

 

[Stewart]

I would use a membrane (Ditra or Dural) and expansion joints at the doorways....

 

[DHTiling]

Hi.

What screed is it. ?

 

[MISSTEE38]

Hi i think its the one people mention on here alot, but don't know the proper name, is it anhydralite or something like that..??!! Sorry to be so ignorant but the builders sorted it. It was a liquid screed and it went off in about 3 days, to be able to walk on it. I will ask my builder on monday i think the company who put t in were 'screed it' if that helps. It was 50mm deep.

 

[Time's Ran Out]

The type of screed is important for drying times, surface preparation and adhesive type, but if you have hairline cracks already showing a decoupling membrane such as Ditra matting would be strongly advised.
For the doorways, edges and break areas in the screeding process - movement joints should be continued through to the surface of the marble.

 

[The D]

As above the type of screed is essential to do a comprehensive specification.

 

[Gazzer]

These questions need asking before any other info can be given really. Its important for everyone to know what they are dealing with.

 

[steve187]

Hi and welcome , the floor will need to cool down before tiling, and then the temp. will need to be raised slowly after.

 

[MISSTEE38]

Hi
And thanks for replying, my builder says its a calcium sulphate screed, or gypsom based?? Is that any help? What sort of primer and sealant should I put on? I was sold Larsen white flex adhesive to go withthe marble tiles and a penetrative sealer. But we are not sure about putting a membrane down?
Any advice appreciated. Thanks

 

[MISSTEE38]

Its a calcium sulphate screed if that helps. Thanks for your reply.

 

[Thespanishtiler]

turn off the ufh

test the floor for moisture level with hygrometer to the data relating to the floor you have had laid

if ok to proceed then scrape off any debris and friable material.

sand the floor and vac up the dust

prime to consolodate the subtrate

use nicobond gypfix addy to lay ditra uncoupler

tile with your spf addy

clean and seal

grout and clean

seal

polish

leave 7 days then bring up ufh in 5 degree increments

put exp joints across door ways and bay up any large areas

 

[The Legend; Phil Hobson RIP]

Spanish has nailed it, can't add much to that apart from what type of calcium sulphate? Good luck

 

[MISSTEE38]

Brilliant thank you very much for the good advice. I realise you can't comment on someonelses ability, but do you think i could get my tiler who has never laid tiles on uhf to do this, he has 30 yrs exp and comes highly rec from tile choice but he hadn;t heard about a decoupling membrane, if i purchase it will he be able to lay tiles as normal but on the membrane is there more to it or should i get someonelse with experience?