Anhydrite Screed (gypsum based) - Tile Advice

[High Peak Tiling]

Hi guys.

All the Anhydrite screeds I have done, have UFH (wet) I have always lathered the floor with Weber PR360.
Then applied Ditra with cementious addy.
I have never had any issues, and all the jobs are perfect now as they were when i left. I have even monitored the drying of addy on the primed screed to see if it loosens (doesnt, due to primer sealing/separating the substrate from addy.

I have even left the matting to see if the primer has worked. I physically cant pull the ditra off the floor.

My Question is, even though my method is perfectly fine. Should I start working with primer & gypsum based addy (anhyfix) ??

Thanks in advance.

(My Method: Scrape floor (mutt) Sand floor, Sweep & hoover, Prime lavishly, Apply Ditra/Dura)

 

[High Peak Tiling]

http://www.netweber.co.uk/tile-fixi...-solutions/tiling-onto-anhydrite-screeds.html

Weber's Solution would also to use Set rapid Plus. instead of Spf

 

[Ajax123]

Given that everything is by the book and the screed is sound, dry, clean and properly prepared with a good dose of primer that penetrates well into the screed then there is no reason why this sort of system wont work. However, using this type of system manages the risk rather than eliminates it.

I have always been one for elimination of risk and so my standard recommendation is to use a gypsum based adhesive. I can say that in my time at Gyvlon I probably visited or was made aware of two or three tile failures a week where these sorts of systems were use. I was aware of only 4 tile failures with gypsum based adhesives in the same period.

Since moving to Gypsol I am not aware of a single failure where gypsum based adhesive has been used. That is nigh on 2 years now. I still get regular calls where tiles have failed using cement based systems although I also have to admit that the level of calls for this have reduced also. I believe that this is in part sue to the fact that we do not encourage the use of so called low laitance screeds which can exhibit undesirable effects with drying and primer application.

 

[High Peak Tiling]

Given that everything is by the book and the screed is sound, dry, clean and properly prepared with a good dose of primer that penetrates well into the screed then there is no reason why this sort of system wont work. However, using this type of system manages the risk rather than eliminates it.

I have always been one for elimination of risk and so my standard recommendation is to use a gypsum based adhesive. I can say that in my time at Gyvlon I probably visited or was made aware of two or three tile failures a week where these sorts of systems were use. I was aware of only 4 tile failures with gypsum based adhesives in the same period.

Since moving to Gypsol I am not aware of a single failure where gypsum based adhesive has been used. That is nigh on 2 years now. I still get regular calls where tiles have failed using cement based systems although I also have to admit that the level of calls for this have reduced also. I believe that this is in part sue to the fact that we do not encourage the use of so called low laitance screeds which can exhibit undesirable effects with drying and primer application.

Thanks Alan,
I like your elimination explanation. I shall work up my supplier in terms of price difference and see. The job is a pool surround.. so not worth taking a 'risk'

 

[Ajax123]

Thanks Alan,
I like your elimination explanation. I shall work up my supplier in terms of price difference and see. The job is a pool surround.. so not worth taking a 'risk'

are you saying the anhydrite is around a swimming pool??

 

[High Peak Tiling]

are you saying the anhydrite is around a swimming pool??

The floor surrounding the pool isn't Gyp. But the whole area to be tiled at once is a mix of both.

 

[widler]

Hi guys.

All the Anhydrite screeds I have done, have UFH (wet) I have always lathered the floor with Weber PR360.
Then applied Ditra with cementious addy.
I have never had any issues, and all the jobs are perfect now as they were when i left. I have even monitored the drying of addy on the primed screed to see if it loosens (doesnt, due to primer sealing/separating the substrate from addy.

I have even left the matting to see if the primer has worked. I physically cant pull the ditra off the floor.

My Question is, even though my method is perfectly fine. Should I start working with primer & gypsum based addy (anhyfix) ??

Thanks in advance.

(My Method: Scrape floor (mutt) Sand floor, Sweep & hoover, Prime lavishly, Apply Ditra/Dura)

Funny thing is, you are not meant to use cement with gypsum, yet you can skim s/c roughing on with British gypsum skim, then tile on top of gypsum skim using cement based addy, seems weird but there must be method in the madness somewhere ?????

 

[High Peak Tiling]

Funny thing is, you are not meant to use cement with gypsum, yet you can skim s/c roughing on with British gypsum skim, then tile on top of gypsum skim using cement based addy, seems weird but there must be method in the madness somewhere ?????

surely the skim would react?

 

[widler]

Nope,skimmed many damp courses,full houses with s/c waterproof roughing on over the years,only thing skim perishes with is damp and/or age ,same as owt really

 

[jonnyc]

After many years working out what is best for me , I only go for anhyfix adhesive to fix ditra mat down and then fix tiles/stone on top of ditra.
encouraged that there seem to be nil failureS when using anhyfix or similar.
not everyone will use ditra but I feel safe with this method

 

[Dave]

surely the skim would react?

If the cement is cured , then no reaction by skimming to render but adding cement based to gypsum background is where ettrignite can form .

 

[High Peak Tiling]

I pay roughly £14 per bag for spf, but my supplier charges £21.33 for anhyfix.. big different on material price

 

[Dave]

I pay roughly £14 per bag for spf, but my supplier charges £21.33 for anhyfix.. big different on material price

I Still use acrylic primer and cement based adhesive method... And I also uncouple all anhydrite floors I tile , call it over kill but I like to work that way..

still yet to use a gypsum adhesive .

 

[High Peak Tiling]

I Still use acrylic primer and cement based adhesive method... And I also uncouple all anhydrite floors I tile , call it over kill but I like to work that way..

still yet to use a gypsum adhesive .

I am Matting the floor anyhow for expansion movement

 

[High Peak Tiling]

i haven't used the gypsum stuff either