Anhydrite screed

[paulpa]

WOW and i thought BAL were expensive. No competition i guess.

 

[paulpa]

Worth posting i thought. Found on my travels
Broken Link Removed

 

[Ajax123]

I wrote that

 

[Ajax123]

Another interesting point is: Walls are rendered with sand/cement yet plastered with Gypsum.
I have never come across the plaster separating from the render??

Am i worrying about something that happens to a small % of jobs most likely having not prepared the site in the 1st instance.
What do the Europeans use, they use more anhydrite than the UK and in general more tiles too.

There are far more gypsum addys available in europe..... Weber, pci, forbo, uzin, kreutz, mapei, benfer to name just a few.

 

[Ajax123]

The two most common in the uk are creative impressions gbta and nicobond gypfix

 

[paulpa]

The downside with Gypsum i guess is the water issue.

 

[The Legend; Phil Hobson RIP]

I wrote that

Ah that clears up a point for me Alan, I have just received my copy of Tiling to calcium sulfate screeds, published by the tile association. And I noticed there was no mention of decoupling membranes, unless I missed something. And yet a few years ago I was involved in laying a large tiled floor on a calcium sulfate screed at a college where the college "boffin" checked the residual moisture levels with his hair hygrometer, we primed the floor with an epoxy primer, then used Ditra mat prior to tiling,

This was specified by Ardex, was this overkill? I understand the need for decoupling on sand and cement screeds, due to shrinkage etc, but just wondered is it not needed on calcium sulfate screeds?

Thanks in advance, Phil.

 

[paulpa]

I can't see the point, if it is being used to separate the cement adhesive from the gypsum because what do you stick the matting with in the first place???
I spoke with Ardex today who were really helpful, the chap never mentioned it once.

 

[PHG Dave]

Ah that clears up a point for me Alan, I have just received my copy of Tiling to calcium sulfate screeds, published by the tile association. And I noticed there was no mention of decoupling membranes, unless I missed something. And yet a few years ago I was involved in laying a large tiled floor on a calcium sulfate screed at a college where the college "boffin" checked the residual moisture levels with his hair hygrometer, we primed the floor with an epoxy primer, then used Ditra mat prior to tiling,

This was specified by Ardex, was this overkill? I understand the need for decoupling on sand and cement screeds, due to shrinkage etc, but just wondered is it not needed on calcium sulfate screeds?

Thanks in advance, Phil.

All screeds have the potential to crack, as unfortunately found out by a previous customer of mine that decided against my recommendation to use decoupling membrane on her Anhydrite screed floor. Luckily the crack in her tiles only covered a few pieces and i still had just enough stock of the same batch to get a match

 

[paulpa]

What do you stick the membrane to the Anhydrite screed?
And can 600 x 300 tiles be laid on them?

 

[The Legend; Phil Hobson RIP]

All screeds have the potential to crack, as unfortunately found out by a previous customer of mine that decided against my recommendation to use decoupling membrane on her Anhydrite screed floor. Luckily the crack in her tiles only covered a few pieces and i still had just enough stock of the same batch to get a match

As I understand the characterisics of Calcium Sulfate screeds, are and I quote from the TTA paper "minimal shrinkage, negligible cracking and curling", so I asked the question, are decoupling membranes necessary? with Calcium Sulfate screeds?

PS I have been a great advocate of decoupling membranes on any suspect substrate, but I am now wondering if I am giving the wrong advice to customers.

 

[Ajax123]

Ah that clears up a point for me Alan, I have just received my copy of Tiling to calcium sulfate screeds, published by the tile association. And I noticed there was no mention of decoupling membranes, unless I missed something. And yet a few years ago I was involved in laying a large tiled floor on a calcium sulfate screed at a college where the college "boffin" checked the residual moisture levels with his hair hygrometer, we primed the floor with an epoxy primer, then used Ditra mat prior to tiling,

This was specified by Ardex, was this overkill? I understand the need for decoupling on sand and cement screeds, due to shrinkage etc, but just wondered is it not needed on calcium sulfate screeds?

Thanks in advance, Phil.

I was also on the steering comittee that wrote that document phil. The uncoupling membranes were not included as the comittee deemed them outside of the scope of the document. The main issue i think is that they sit outside of the british standards.

 

[Ajax123]

The downside with Gypsum i guess is the water issue.

.???????

 

[Ajax123]

As I understand the characterisics of Calcium Sulfate screeds, are and I quote from the TTA paper "minimal shrinkage, negligible cracking and curling", so I asked the question, are decoupling membranes necessary? with Calcium Sulfate screeds?

PS I have been a great advocate of decoupling membranes on any suspect substrate, but I am now wondering if I am giving the wrong advice to customers.

Uncoupling membranes certainly have a place with calcium sulphate screeds but there is less lateral movement so they are not so necessary from this point of view. Where a screed is laid without appropriate joints they are useful and where there is differential thermal movement between screed and adhesive. The gypsum addys (gbta) actually state that they can be used in place of uncoupling.

If the substrate is as you say suspect then my advice is uncople...

 

[Ajax123]

What do you stick the membrane to the Anhydrite screed?
And can 600 x 300 tiles be laid on them?

Either with gypsum adhesive, cement based adhesive on a primer or with a vynil floor type adhesive.

 

[Ajax123]

Either with gypsum adhesive, cement based adhesive on a primer or with a vynil floor type adhesive.

And yes to the second question

 

[paulpa]

So would i be right in saying it could be laid in my case on Anhydrite with say an [h=1]Acrylic Floor Covering[/h]Say this or another rather than "tile adhesive"

 

[paulpa]

For anyone else in my situation (Anhydrite Screed) i have decided to go with a Gypsum adhesive.
Hopefully it will turn out to be the correct decision in the long term.
I will update on progress and any issues i face.
My other options being considered were cement based adhesive on a primer or Ditra matting (or carpet ;-)
Now to open the wallet and give it a hammering again.

 

[paulpa]

To add to this.
Having received a copy of the Tile associations paper titled "Tiling onto Calcium Sulphate Based Screeds"
They recommend using a polymer modified cementitious adhesive over a primed surface. No mention of Gypsum based adhesives!

 

[Ajax123]

They decided not to include gypsum because they wanted the document to reflect materials covered by a british standard. There is currnently no britsh standard covering gypsum despite it meeting all the same requirements as the flexible cement adhesives. There is a phrase in the document which says along the lines of other systems or adhesives which are not covered by british standards are available. This was negotiated into the document to cover other than cement adhesives but the tiling association steering committee were very intransigent on the point. There were no members on the steering comittee from companies that have gypsum adhesives available in the uk. Nicobond developed theiers following input from myself having spotted an important gap in the market.

 

[DHTiling]

But there is on the inside of the front cover a full page advert for gypfix ?

 

[paulpa]

Daft question maybe but having never used it..................................... Coving adhesive can be bought as a gypsum adhesive (powder form), Does this have any similarities with a gypsum tile adhesive?


Does seem a confusing issue, just glad i looked into it before tiling.

 

[Ajax123]

Coving adhesive would certainly stick the tiles as would plasterboard adhesive. Problem i would envisage would be the cohesive bond strength within the adhesive itself. That said .... Never tried it so dont know

 

[Ajax123]

But there is on the inside of the front cover a full page advert for gypfix ?

Paul dawtrey, export director for nicobond, was on the same comittee. It was him that spotted the opportunity and went ahead with the gypfix project.

 

[paulpa]

surprised others have been so slow. Looks an obvious target market to me.