A few questions before laying tiles

[freddyq]

Hi all, this is my first post on here although in attempting to Google answers to my questions I have come across several threads on this forum already which were really helpful. So now I thought it'd help to get advice specific to my situation...so here goes. These are all in relation to an extension where the floor area to be tiled is about 31m2 split into three rooms with wet underfloor heating throughout. We've chosen porcelain floor tiles.

1. We had 65mm traditional sand and cement screed laid down just under 4 weeks ago. To date, we've just kept windows slightly open to keep the area well ventilated to help the screed dry but after the 4 week point can I start turning the UFH on at a low temperature to speed up the drying process? Or should I leave it alone?
2. How soon can I get the tiles laid? I can't really afford to wait 1 day per mm which seems to be the normal logic...
3. Should I have ditra mat laid on the screed before the tiles go on? It seems the answer to this question is yes from what I've read on here already (due to both protection from rising moisture as the screed fully dries over the coming months and to protect my tiles from cracking as the screed moves around) so my only follow up would be does ditra mat affect the performance of UFH in any way?
4. What's the best primer for my screed and what's the best glue to use to put down the ditra mat and for the tiles?

Thanks in advance!

 

[Albert]

You could try flexbone https://www.ctdtrade.co.uk/bal-flexbone-2easy-20m-roll

 

[freddyq]

You could try flexbone https://www.ctdtrade.co.uk/bal-flexbone-2easy-20m-roll

That looks good although quite pricey. Are you recommending that because my screed is only 4 weeks dry? What advantages does this have over Ditra mat? I don't mind spending money for the right thing but Ditra mat seems tried, tested and highly rated whereas this is much more expensive and mixed opinions on it...

 

[CJ]

Start ufh at low temp......then run for a few weeks. Then, as mentioned, Bal flexbone, which allows the screed to breath

 

[freddyq]

Start ufh at low temp......then run for a few weeks. Then, as mentioned, Bal flexbone, which allows the screed to breath

Thanks...still curious to understand advantages of Bal flexbone over Ditra mat.

 

[CJ]

flexbone can go down sooner, and is loose laid. Ditra matting needs to go on a bed of adhesive, so you will have to wait.

 

[freddyq]

flexbone can go down sooner, and is loose laid. Ditra matting needs to go on a bed of adhesive, so you will have to wait.

Ah right, so the screed needs to be fully dry before the adhesive would have to go on for the ditra mat?

 

[CJ]

Ah right, so the screed needs to be fully dry before the adhesive would have to go on for the ditra mat?

Basically, yes.

Flexbone allows the floor screed to continue to cure.

 

[freddyq]

Basically, yes.

Flexbone allows the floor screed to continue to cure.

Thanks CJ, think I will go with that then. Presumably it doesn't reduce the performance of underfloor heating?

Cheapest I'm seeing it anywhere currently is Topps Tiles which I wouldn't expect. Unless someone knows of a cheaper supplier...

 

[Dumbo]

Schuter state you can fix ditra mat to screed as soon as it is weight bearing .it also allows screed to breath

 

[freddyq]

Schuter state you can fix ditra mat to screed as soon as it is weight bearing .it also allows screed to breath

So now I'm confused! Although Not covering the screed with adhesive until it's fully dry does make sense to my layman mind, how is it meant to be able to breathe?

 

[Dumbo]

The is a cavity membrane that has vapour release channels . But you do need to get your uh fully commisioned first

 

[freddyq]

So I just called Schluter and spoke to technical support - I explained my screed is about 4 weeks dry and I want to put the tiles down in the next week or so. They told me as long as I use any C2 breathable adhesive it will allow moisture from the screed to continue to escape after tiling and then the ditra matting and it's vapour channels will do their job. So they say Ditra can be laid on a screed which isn't fully dry. Thoughts?

Or should I just put the flexbone 2Easy matting down...?

 

[Dumbo]

Thoughts are 2e has been around For years and is made by gutjahr . If it wasnt for bal running a succesfull marketing campaign this product woudnt of been mentioned

 

[freddyq]

Thoughts are 2e has been around For years and is made by gutjahr . If it wasnt for bal running a succesfull marketing campaign this product woudnt of been mentioned

So is it not a good product? Just backed by a big marketing campaign? You think I should go with Ditra and a breathable adhesive...?

 

[widler]

Flexbone is extremely expensive for what it is .
Ditra and tile , you will be fine, your ufh will help with the drying time , most tilers have tiled onto green screeds over the years with no problems .
Or spend a nice weeks holiday money on flexbone .
Which is basically ditra with some scrim stuck on it (it’s actually not at all like ditra, ditra would be much more expensive to manufacture than flex, but is a good few £ cheaper, ps there’s also cheaper matting than ditra as well )

 

[freddyq]

Flexbone is extremely expensive for what it is .
Ditra and tile , you will be fine, your ufh will help with the drying time , most tilers have tiled onto green screeds over the years with no problems .
Or spend a nice weeks holiday money on flexbone .
Which is basically ditra with some scrim stuck on it (it’s actually not at all like ditra, ditra would be much more expensive to manufacture than flex, but is a good few £ cheaper, ps there’s also cheaper matting than ditra as well )

Thanks for this - very helpful for a complete layman! What's the cheaper matting and I suppose it will have some downsides compared to ditra?

 

[Dumbo]

Dural ci matting, no downside

 

[freddyq]

Dural ci matting, no downside

Interesting - thanks I'll look into it. If there's no downside, why is it cheaper? Is it because Ditra is German-made so more of a premium on it?
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Turns out because of the quantity I need, I can get the Ditra matting for a lower price/m2 which means it'll cost the same as the best price I can find for the Dural CI matting. Assuming they are both the same I might as well go for Ditra I suppose...

The marketing material for the Dural matting does state quite clearly that tiles can be laid as soon as the screed is hard enough to take load (i.e. not fully dried) so I like that because that's one of my main concerns..

 

[freddyq]

Is there a recommended C2 breathable adhesive to fix the Ditra matting onto my screed?