Anhydrite Screed

[Just Rizzle]

since 1982 I've been doing tiling as profession. I first learnt to tile using sand and cement. ive worked on some large projects in my time .shopping centers. prisons . listed buildings such as the. natural history museum allot of these projects had some of the meanest quantity surveyors in the game. if it wasn't right you didn't get paid.
all the time I've been tiling I've been learning so my knowledge of my profession isn't just family bathrooms.

anhydrites unfortunately are here to stay and if your going to tile them you need to get it right. if you don't you are the one the customer is going to come after .
I've done a fair bit of research on these screeds and been on a course to explain the pros and cons of using them.
the course was about 8 yrs ago. my conclusion from talking to reps technicians with adhesive manufacturers is this

under no circumstances should cement based adhesives be used on anhydrite floors there's simply to much risk of failure no matter how many coats of primer you wish to put on prior to tiling. I recommend tilemaster because they give me confidence in there products. and there easy to get hold of and talk to. there are other anhydrite addy manufacturers but were I live there hard to get hold of.
weber do a anhydrite addy but its not available as yet in the uk, for some reason, so that's why they recommend there spf.

what I try to do is give best advice to people who are less experienced as me.
p s theres only one on this site that's full of it

 

[bcd-87]

@Dave stephen hawking him

 

[widler]

Ray, so what your saying is Tilemaster is the best adhesive for anhydride screed, why is it the best?
So do we now take it as read, that the only opinion that matters on the subject of adhesives is yours?

I would of thought that its best to use the right adhesive with the right substrate, i know u can use cement addy on anhydrite, it says so on the bag, it also says on a lot of stuff to PVA 1st
I would of thought all us pro tilers on here , who go on about the belt and braces approach whould welcome Anhydrite addy as its the correct addy for the right substrate
if one fails with cement addy the addy manufacturer will no doubt say you have used the wrong addy

 

[CJ]

All very well using the stuff, but I've never even seen it in my area.

 

[StevieBoy]

Ive recently laid 2 of these floors. I scraped off all the laitence, but most of it had come loose it anyway by the time the plasterers / chippys and everyone else had finished walking all over it, then hoovered it clean, then gave it two coats of diluted BAL SBR rollered on in opposite directions.

Then tiled it with slowset flexible from Topps, which is made by Palace.
Grouted with BAL flexible wide joint grey grout, and after 3 months all is still ok.

 

[widler]

This is all well and fine , is this not the old
'ive done it for years and never had a problem' senario ??
again, remember pva , it was fine to tile onto for years, but now

You watch, in a year or two they will tell you that you can't use cement addy on gypsum screeds

 

[Ian]

This is all well and fine , is this not the old
'ive done it for years and never had a problem' senario ??
again, remember pva , it was fine to tile onto for years, but now

You watch, in a year or two they will tell you that you can't use cement addy on gypsum screeds

I'm with @widler on this one, why would the adhesive manufacturers spend £1000's and goodness only knows how much time developing products specifically for these screeds, if something they already produce is perfectly suitable?

 

[StevieBoy]

Guide: Tiling On Anhydrite Floor Screed | Palace Chemicals Ltd

 

[widler]

Ok im giving up, i will use gypsum addys made for the job, you lot stick it to neat primer

 

[StevieBoy]

Lol

 

[AD Ceramics]

In theory is it not just like tiling on a plastered wall, you prime that to form a barrier between gypsum and cement? Who u uses these adhesives on walls?

 

[Just Rizzle]

if you reed the palace recommendations and all the other cement based addy manufacturers, what they are saying is to put a barrier between the addy and the screed so the addy sticks to the barrier not the screed.
with the gypsem based addys they are bonding with the screed not the barrier so forming a better adhesion so making the tiles more secure to the floor and in my honest opinion less likely of failing ,and less likely of you getting a call back from your clients

I understand a recent program on grand designs has had a failure where the tiler fix on anhydrite using a cement based addy

 

[widler]

In theory is it not just like tiling on a plastered wall, you prime that to form a barrier between gypsum and cement? Who u uses these adhesives on walls?

Not really as you can skim onto s/c roughcoat with no problems , completely different substrates , if they were the same they would just pump multifinish onto the floor

 

[widler]

Shoot, ive posted again, bloody still askeep

 

[Tile Shop]

But the whole point is that because the screed is porous the primer will key in. If thats well bonded to the surface there won't be any issue of it coming loose or failing. So it will prevent the gypsum reacting with the cement but the adhesive is still sufficiently stuck down.

I mentioned in a previous post 2 possible pitfalls of using the anhyfix, gypfix or whatever your weapon of choice is, and the users of it didn't jump up to defend it.

Crystalisation occurs when gypsum comes into contact with cement yes? My first point was that grouts are cement based and will come into contact with the adhesive...... see the possible problem?

Next, you can't afford for the addy to get wet. So never mop a floor again?

I am going by what i've been told tech-bods from several places. So i'm 100% behind the cement and primer because we know it works.... but i'd love someone to now defend the gypsum addy's and tell me i'm wrong, then maybe i'll have the confidence in selling the stuff.

 

[widler]

Id like to know tilemasters stance on this, the folks who go to great lengths and money to make these addys what are really no use to no one
ps, paul c we know that cement addys work with the right prep , but im playing a augumentitive barsteward with the 'we have to move with the times' tilers , those on here who bang on about what we are supposed to use and not use on different substrates , yet when one comes out which is made for the substrate its frowned upon and not needed?
As for the grout problem im sure the scientists who make this stuff have thought of that , tested it and deemed it ok, or maybe not

 

[AD Ceramics]

Not really as you can skim onto s/c roughcoat with no problems , completely different substrates , if they were the same they would just pump multifinish onto the floor

Why is it ok to skim sand and cement rendered walls then? there is no barrier between the cement and gypsum, ever tried chopping it off it's as hard as a mad mans

 

[Dave]

Why is it ok to skim sand and cement rendered walls then? there is no barrier between the cement and gypsum, ever tried chopping it off it's as hard as a mad mans

When the sand/cement has cured there is no issue with gypsum and portland , its the portland over gypsum that creates the issue..

 

[Just Rizzle]

But the whole point is that because the screed is porous the primer will key in. If thats well bonded to the surface there won't be any issue of it coming loose or failing. So it will prevent the gypsum reacting with the cement but the adhesive is still sufficiently stuck down.

I mentioned in a previous post 2 possible pitfalls of using the anhyfix, gypfix or whatever your weapon of choice is, and the users of it didn't jump up to defend it.

Crystalisation occurs when gypsum comes into contact with cement yes? My first point was that grouts are cement based and will come into contact with the adhesive...... see the possible problem?

Next, you can't afford for the addy to get wet. So never mop a floor again?

I am going by what i've been told tech-bods from several places. So i'm 100% behind the cement and primer because we know it works.... but i'd love someone to now defend the gypsum addy's and tell me i'm wrong, then maybe i'll have the confidence in selling the stuff.

are the tech bods from companies that don't do an anhydrite addy caus there bound to back there products asfor not been able to mop a floor what a load of tosh most floors dry due to evaporation especially with ufh
all the floors ive sceen that have failed have all been due to cement based adhesives.and the builders /tilers not knowing what there laying on. most see a flat floor and think this is gona be easy.
the problem with these floors there a back ward step as the drying times are so long just persuaded a builder to switch to a semi dry screed as his clients want to be in for end November told him that a 65mm anny screed wouldn't be ready till January at the earliest
I actually don't give a monkeys how people tile these floors all im saying is if it pops then the problem is yours and can be expensive

 

[Ian]

Anhydrite can be force dried (with the ufh) in 14 days.

 

[peteablard]

are the tech bods from companies that don't do an anhydrite addy caus there bound to back there products asfor not been able to mop a floor what a load of tosh most floors dry due to evaporation especially with ufh
all the floors ive sceen that have failed have all been due to cement based adhesives.and the builders /tilers not knowing what there laying on. most see a flat floor and think this is gona be easy.
the problem with these floors there a back ward step as the drying times are so long just persuaded a builder to switch to a semi dry screed as his clients want to be in for end November told him that a 65mm anny screed wouldn't be ready till January at the earliest
I actually don't give a monkeys how people tile these floors all im saying is if it pops then the problem is yours and can be expensive

It's the second part of that statement that's the problem. I've heard of floors failing where a gypsum based adhesive was used but the floor hadn't been sanded or primed. If the prep is done right then there is no risk in my opinion. A mate of mine is subbing for a company and is now ripping up the 4th failed floor they've had, all done by different tilers. . Complete lack of knowledge on both sides has been costly for them

 

[mma]

I was picking up some adhesive this morning and I overhead the end of a conversation where the tiles have popped up. Floor hadn't been sanded and cement based adhesive had been used. Gonna be costly for somebody

 

[StevieBoy]

................. A mate of mine is subbing for a company and is now ripping up the 4th failed floor they've had, all done by different tilers. . Complete lack of knowledge on both sides has been costly for them

So that would suggest that the removal or sanding off of the laitence and priming are essential with the idea the primer forms a barrier between the adhesive and the screed

This thread could go on and on like the Sigma / Rubi debate lol.

 

[Ste-G]

Just putting the discussion of adhesive and primer aside for a moment. Does anyone know if the latency can be scraped of the day after the floor is poured. A builder I have a lot of respect for told me this is so, but every time I've fixed on one I've had to sand it.
Are the screeding companies not giving this information or is it just a case of f..k it let the tiler do it.

 

[StevieBoy]

Just putting the discussion of adhesive and primer aside for a moment. Does anyone know if the latency can be scraped of the day after the floor is poured. A builder I have a lot of respect for told me this is so, but every time I've fixed on one I've had to sand it.
Are the screeding companies not giving this information or is it just a case of f..k it let the tiler do it.

I'd be interested to know the answer to this - it may be possible, as I am on my second of four new builds, I went over to the fourth plot yesterday where the flow screed had been poured only a week ago. It looked wet, it wasn't obviously but I scraped a bit with my right foot and the laitence did actually come off.

On the other two plots that I have tiled, I would say 70% of it had actually wore off with all the other trades walking all over it, so I got down on my hands and knees, used a very sharp scraper and it all came off very easily indeed - so didn't need to sand it.