Decoupling matt on screed

[BartW]

Hi,

as per the title, is it absolutely necessary?

 

the screed was installed 7 - 8 months ago (70mm of it). 
 

the floor has water UFH in it. 
 

not sure, but I suspect the screed is anhydrite. 
 

Could anyone share views please?

 

thanks

 

Bart

[nod]

It is necessary 

Nearly every tiling job I price has matting included In saying that I’ve tiled heated floors without it After the customer has signed a waver 

[dpmiller]

what did you do before matting @nod

[nod]

I been tiling for nearly 40 years 

Before flexi adhesive 

We used to screed a floor in the morning and bond the tiles to it in the afternoon 

A lot more skill than now It’s only the last 12 years that’s UFH heating has become mainstream 

Five years ago I tiled a 200 m2 floor that had been down a week and the bio boiler hadn’t been commissioned 

No problems 

But I put Ditra mat down on my own 150 m2 floor 

Will they come up without matting 

Probably not But a ver expensive lesson if they do 

[Vijay]

is the general rule if you have UFH you need a decoupling mat?

[gc100]

If you don’t put in a decoupling matt you will run the risk of tiles lifting/cracking somewhere. Whether it happens is another question..

[MortarThePoint]

This is one of those potentially overlooked costs. Can you get away without it, possibly. Would you kick yourself if you didn't use it and had an issue, definitely. As a self builder you have enough to worry about, so worth including.

 

It does seem rather costly, but maybe I am looking in the wrong place. Looks to cost around £6/m2 or above.

 

On 16/05/2021 at 23:14, nod said:

But I put Ditra mat down on my own 150 m2 floor

 

You have expensive tastes. Just joking, but it must be very good as I can't find it for less than £10/m2.

 

[Pete]

57 minutes ago, MortarThePoint said:

This is one of those potentially overlooked costs. Can you get away without it, possibly. Would you kick yourself if you didn't use it and had an issue, definitely. As a self builder you have enough to worry about, so worth including.

 

It does seem rather costly, but maybe I am looking in the wrong place. Looks to cost around £6/m2 or above.

 

 

You have expensive tastes. Just joking, but it must be very good as I can't find it for less than £10/m2.

 

I got mine on Ebay and saved a bit

[nod]

1 hour ago, MortarThePoint said:

This is one of those potentially overlooked costs. Can you get away without it, possibly. Would you kick yourself if you didn't use it and had an issue, definitely. As a self builder you have enough to worry about, so worth including.

 

It does seem rather costly, but maybe I am looking in the wrong place. Looks to cost around £6/m2 or above.

 

 

You have expensive tastes. Just joking, but it must be very good as I can't find it for less than £10/m2.

 

I normally pay about £5 m2 

CTD 

 

Edited May 18, 2021 by nod

[Pocster]

Decoupling Mat 100% required 

@nod ctdtiles ? . Couldn’t see it 

[MortarThePoint]

25 minutes ago, pocster said:

Decoupling Mat 100% required 

@nod ctdtiles ? . Couldn’t see it 

 

I couldn't find it on the website either so called. DITRA 30m roll for £6.67+VAT / m2 as a starter. Thanks @nod.

Edited May 18, 2021 by MortarThePoint

[Pocster]

Just now, MortarThePoint said:

 

I couldn't find it on the website either so called. DITRA £6.67+VAT / m2 as a starter. Thanks @nod.

Did look on eBay and can see £6 a sq m - inc vat for an unbranded equivalent . .Assuming they can give a receipt can get the vat back 

[MortarThePoint]

I don't know if the stuff below is any good, but I guess it doesn't decouple. Only £2.87/m2 though.

 

"Kerakoll Biotex Anti Crack Matting is a reinforced anti-cracking sheet matting, for evening out tensile and sheer movements between the substrate and the surface finish. Also suitable for use as an anti-cracking product for tongue-and-groove hardwood floors on critical substrates. For internal floors. Previously known as Kerakoll Idrobuild Tex Matting"

 

https://www.tilingsuppliesdirect.co.uk/product/kerakoll-biotex-anti-crack-matting#.YKO0bahKhaQ

[Pocster]

1 minute ago, MortarThePoint said:

I don't know if the stuff below is any good, but I guess it doesn't decouple. Only £2.87/m2 though.

 

"Kerakoll Biotex Anti Crack Matting is a reinforced anti-cracking sheet matting, for evening out tensile and sheer movements between the substrate and the surface finish. Also suitable for use as an anti-cracking product for tongue-and-groove hardwood floors on critical substrates. For internal floors. Previously known as Kerakoll Idrobuild Tex Matting"

 

https://www.tilingsuppliesdirect.co.uk/product/kerakoll-biotex-anti-crack-matting#.YKO0bahKhaQ

LOL!. Now it's too cheap!. I can't see from the photo it has the 'fleece' side. You buy some and tell me how you get on ?

[MortarThePoint]

2 minutes ago, pocster said:

LOL!. Now it's too cheap!. I can't see from the photo it has the 'fleece' side. You buy some and tell me how you get on ?

 

Just reinforcement I think:

https://products.kerakoll.com/en-GB/p/biotex

[MortarThePoint]

Some options here: https://www.protilertools.co.uk/categories/materials/tile-matting

 

Durabase is thicker (4mm) than DITRA (3mm) and about 10% cheaper.

 

There are a couple of uncoupling mats that are less than 1mm thick and quite cheap (<£5/m2), but that's not much room to do a good job of uncoupling.

 

If @nod used DITRA on his own house I think that says a lot.

[Pocster]

3 minutes ago, MortarThePoint said:

Some options here: https://www.protilertools.co.uk/categories/materials/tile-matting

 

Durabase is thicker (4mm) than DITRA (3mm) and about 10% cheaper.

 

There are a couple of uncoupling mats that are less than 1mm thick and quite cheap (<£5/m2), but that's not much room to do a good job of uncoupling.

 

If @nod used DITRA on his own house I think that says a lot.

https://www.ebay.co.uk/itm/353070075797?ul_noapp=true

 

This one I emailed. Will provide a VAT receipt. Also 5% discount if you spend over £100.

[MortarThePoint]

1 minute ago, pocster said:

https://www.ebay.co.uk/itm/353070075797?ul_noapp=true

 

This one I emailed. Will provide a VAT receipt. Also 5% discount if you spend over £100.

 

Looks the part. At £5/m2+VAT I'd rather DITRA though even if it's a little more expensive. 

[Pocster]

2 minutes ago, MortarThePoint said:

 

Looks the part. At £5/m2+VAT I'd rather DITRA though even if it's a little more expensive. 

True. As you know the product you are getting.

[Pocster]

@BartW I went for it and bought the eBay mat . Not laid any yet but seems the same as the ditra though perhaps the plastic feels cheaper . Fleece is the same .

For me that’s a saving of around 600 quid .

[MortarThePoint]

7 hours ago, pocster said:

For me that’s a saving of around 600 quid

 

Was that for >300sqm then or did you get the eBay price even lower than £4.75/sqm+VAT?

[Pocster]

37 minutes ago, MortarThePoint said:

 

Was that for >300sqm then or did you get the eBay price even lower than £4.75/sqm+VAT?

eBay price 

[Adsibob]

So will Ditra add 3mm to the build up? Or does it absorb most of the adhesive such that it doesn’t impact Finished Floor Level?

[Pocster]

43 minutes ago, Adsibob said:

So will Ditra add 3mm to the build up? Or does it absorb most of the adhesive such that it doesn’t impact Finished Floor Level?

I’d say 3mm ish if you stick it down with glue rather than tile adhesive 

[Nickfromwales]

Make sure you don’t go off the straight line when laying or it’ll quilt up and then you’re into cutting out sections and patching. It’s quite hard to spot too, so keep checking back on the previous runs to ensure they’ve stayed down. 
A cheap 9” roller will help to lay it smoothly. 
FWIW, I’ve laid Christ-knows how many floors without Ditra / other and not lost any of them ever. My golden rule is prepping and never laying onto a dry / dusty / contaminated subfloor. I have seen others lay directly onto screed which has been too long on site / not laid quick enough and the tiles + adhesive + top skin of screed has come up one one big sandwich. Screed needs to be sound, prepped properly, and bingo. 
I’ve only ever used a mat over unknown sub base or liquid screeds. 

 

Edited August 8, 2021 by Nickfromwales