Mapeii does not reccomend on Ditra !

[m3fitter]

Is it me, or am I missing something ?? Mapeii technical say that their rapid set is fine for Anhydrate screed but isn't suitable for laying on ditra !! and Ardex X7R is suitable for Anhydrate screed and ditra... ??

 

[charlie1]

Not sure but x7r is one of the most impressive rapid sets I have ever used... But that's for another thread... Continue

 

[High Peak Tiling]

is the anhydrite substrate primed before the application of mapeii rapid?

 

[m3fitter]

I checked this all out, prior to ordering the sticky.. the screed is well scraped of surface scum, acrylic primed.. mapeii is cool with sticking the ditra, but not cool with sticking anything on top of ditra... its madness !! I double checked this with someone else in their technical dept. !

 

[Concrete guy]

I'm not a huge fan of Ditra matting. My distrust of this product though stems back 20 years when it was completely and entirely misunderstood.

Shops were selling it as some form of super replacements for all sorts of solid substrate suggesting you could use this stuff to tile straight on floorboards, floating floors the lot. I had to correct so many failures.

So rather than become misinformed I spent a long time on the phone (at the time) with Schluter technical. Fortunately now much of this information is available in easy downloads - here's a great info sheet:-

http://www.schluter.com/media/DITRAHandbook-ENG-2013.pdf?v=201306080603

If you look through you will see without exception that the tile is fitted over the Ditra with unmodified thin set mortar. That means no polymer additives at all to comply with the correct installation guides of Schluter.

Things have developed a lot since I stopped fixing but certain constants remains, if I understand this correctly, once you used a polymer modified adhesive on top of Ditra matting the uncoupling mechanism ceases to work or is reduced in efficacy substantially. In so much as it's no longer truly operating as a decoupling membrane.

How does this then dovetail with the BS standards requiring polymer modified adhesives to be used in these situations particularly with UFH?

 

[Rizzle from the Portizzle]

I'm not a huge fan of Ditra matting. My distrust of this product though stems back 20 years when it was completely and entirely misunderstood.

Shops were selling it as some form of super replacements for all sorts of solid substrate suggesting you could use this stuff to tile straight on floorboards, floating floors the lot. I had to correct so many failures.

So rather than become misinformed I spent a long time on the phone (at the time) with Schluter technical. Fortunately now much of this information is available in easy downloads - here's a great info sheet:-

http://www.schluter.com/media/DITRAHandbook-ENG-2013.pdf?v=201306080603

If you look through you will see without exception that the tile is fitted over the Ditra with unmodified thin set mortar. That means no polymer additives at all to comply with the correct installation guides of Schluter.

Things have developed a lot since I stopped fixing but certain constants remains, if I understand this correctly, once you used a polymer modified adhesive on top of Ditra matting the uncoupling mechanism ceases to work or is reduced in efficacy substantially. In so much as it's no longer truly operating as a decoupling membrane.

How does this then dovetail with the BS standards requiring polymer modified adhesives to be used in these situations particularly with UFH?

would a polymer modified adhesive be your avarage porcelain adhesive

 

[m3fitter]

well.. it does not.. ! so Ardex x7R is totally a different item, I think not.... I only checked this, as the client is a Techi, and has "RESEARCHED" on the internet, and has asked me to clarify and guarantee my products that I am supplying.. as if trying to catch me out.. hahhaa, the ufh is under, anhydrate screed, the tile is 20mm 900x600x20 dense limestone... back in the day, I would have just used flex rapid full stop.. these days, its all about accountability and technicality..based upon info the client is reading..

 

[Peter]

Schluter UK and Schluter USA give quite different advice which is odd. Modified in the UK and unmodified in America if I recall correctly.

 

[Concrete guy]

would a polymer modified adhesive be your avarage porcelain adhesive

As far as I understand, yes.

 

[Concrete guy]

Schluter UK and Schluter USA give quite different advice which is odd. Modified in the UK and unmodified in America if I recall correctly.

Please bear in mind I'm now talking about conversations that took place nearly two decades ago. Also the last time I used Ditra it looked like a corrugated sheet not lots of little squares stamped into a sheet.

The explanation I was given by Schluter at the time was that the polymer additive in the adhesive improved bonding to a degree that it bonded completely to the matting thereby negating (or at least substantially reducing) it's decoupling performance.

The mechanism by which the decoupler works is the unmodified cement adhesive sets in a perfect match to the form of the matting, think of it like a perfect bed of adhesive shaped exactly to fit the matting itself and it locks in like a key - perfectly. But it doesn't bond completely to the Ditra.

The shear movement is allowed because the bond isn't complete - the mat can move very slightly without pulling the adhesive (and therefore tile) with it.

Once you introduce enhanced adhesion (polymer additives) the adhesive sticks to the mat like poo to a blanket and it's no longer really decoupled.

Has anything changed in the last 15 to 20 years to alter this?