Alfa Heavy Anhydrate.

[CJ]

Anyone heard of it?

looks like an ordinary screed. No laitence.

 

[Stef]

Alan's (Ajax) your man for this!!

 

[Ajax123]

Had to laugh .... Sorry.... No offence.

It's alpha hemi hydrate. And it is a calcium sulphate screed. It will have Laitance but it will not be a soft friable Laitance. In terms of prep it should be treated the same as any other calcium sulphate screed. I.e. Sand it, vac it, dry it, heat it and cool it (if heating is present), test it for residual moisture and if dry prime it as appropriate and tile it

 

[Stef]

Alan, sorry to hijack this but how soon can I remove laitance from a Gyvlon, poured on Monday 55mm.
Does this cold weather affect the drying times of calcium screeds?
Heating hopefully going on end of next week.

 

[Ajax123]

Alan, sorry to hijack this but how soon can I remove laitance from a Gyvlon, poured on Monday 55mm.
Does this cold weather affect the drying times of calcium screeds?
Heating hopefully going on end of next week.

Typically removal would be about 5 to 7 days.

yes cold weather will affect the drying time. 1mm per day up to 40mm and 2 days per mm there over in hood drying conditions at 20oC and 60%rh. We have neither at present so drying rates will be slower and drying times longer. Force drying with the heating will help enormously.

 

[CJ]

Had to laugh .... Sorry.... No offence.

It's alpha hemi hydrate. And it is a calcium sulphate screed. It will have Laitance but it will not be a soft friable Laitance. In terms of prep it should be treated the same as any other calcium sulphate screed. I.e. Sand it, vac it, dry it, heat it and cool it (if heating is present), test it for residual moisture and if dry prime it as appropriate and tile it

I was close.

Job I looked at today......has this stuff, (although it does look like an ordinary screed, no laitence) ...with piped UFH

I explained the procedure to the customer, (mech sanding, Hoover, prime) so he phoned the company there and then......and this company told him it "just needs priming"

This floor has been down 3 months (so he told me)

 

[Ajax123]

I was close.

Job I looked at today......has this stuff, (although it does look like an ordinary screed, no laitence) ...with piped UFH

I explained the procedure to the customer, (mech sanding, Hoover, prime) so he phoned the company there and then......and this company told him it "just needs priming"

This floor has been down 3 months (so he told me)

i have heard this a number of times recently and I think there is a knowledge gap with the reps who supply the binder in terms of floor coverings. It is fair to say that it probably won't have a loose friable Laitance but Laitance is a function of migration of bleed water. Even sand cement screeds produce a Laitance. The advice of the contract flooring association, the tiling association, the adhesive and primer manufacturers and all of the industry experts is that it should be sanded. If you don't and it fails, do you think the company that told him "just needs priming" will be willing to stand by your side and defend you. And how successful do you think they would be with all of the other experts agreeing it should have been sanded. For the sake of what it costs why would your client want to risk that scenArio.

 

[beanz]

Alan, if it's not a "loose friable laitance" why would it fail? Don't get me wrong, I'm not disagreeing with you, just trying to understand the process!?!

 

[Ajax123]

Alan, if it's not a "loose friable laitance" why would it fail? Don't get me wrong, I'm not disagreeing with you, just trying to understand the process!?!

Because there is often very fine dust on the surface of these screeds which can interfere with the penetration of primers. Also the screed has been in a construction site for a number of weeks or months and will have surface contamination from extraneous materials e.g. Mud, plaster, mortar, paint etc etc. Also the surface of these screeds can be very hard and very dense which further interferes with the penetration of primers. Sanding opens the surface texture and subsequently provides a mechanical key for said primers etc. it also opens the surface to promote faster drying. I can obviously only offer guidance based on experience and the national and industry best practice codes. It may be that if you tile it you would get away with it and it would not fail. But, if it does, you would stand alone in sorting it out because the first questions you would be asked would include "did you sand the screed as per the instructions of the tiling association guide to tiling to calcium sulphate screeds and as per the instructions on pretty much every bag of tile adhesive in relation to these screeds" I know that is what I would ask....


sanding is is not just to remove Laitance but is to prepare the screed to receive bonded floor coverings...

 

[Stef]

Alan is there any other level screeds on the market that dry quicker than a calcium screed?
Or can be tiled quicker I should say.

 

[Ajax123]

Alan is there any other level screeds on the market that dry quicker than a calcium screed?
Or can be tiled quicker I should say.

Yes but there are always trade offs. There are cement based screeds that dry in hours rather than days but they are expensive and don't offer benefits of depth reduction and the environmental aspects. There is not a fast drying pourable cost effective screed that can be laid very thin and offers all the advantages that anhydrite gives. That would be utopia but to be fair the Gypsol technical bowfins are working on it. We can produce an anhydrite screed that dries very fast but is not pourable so only gets us half way there. Still....small steps eh!

 

[CJ]

These newer pourable screeds do look like an ordinary sand/cement screed. Sometimes unless it's obvious, we could end up in the cack.

 

[Ajax123]

These newer pourable screeds do look like an ordinary sand/cement screed. Sometimes unless it's obvious, we could end up in the cack.

Hemi I hydrates will often look like cement screeds in colour because there is often a small amount of cement in them. The colour is also affected by the sands used. I have seen a few in the south west that use a very dark sand which makes them look dark grey.

 

[Ajax123]

These newer pourable screeds do look like an ordinary sand/cement screed. Sometimes unless it's obvious, we could end up in the cack.

Thats why you need to ask the questions...

 

[CJ]

Thats why you need to ask the questions...

I always do......but quite often, they don't have a clue.
I'm in the South/West, and this particular floor DOES look like a standard cement screeded floor. Surprisingly, they told ME!

 

[Rizzle from the Portizzle]

for gods sake again and again this could be solved in a moment if only the screed layers would stamp there floors when layed or after they set with a batch number type and contact email site using batch number on email site to descibe the screed and requirerments to fix tiles even if its been capeted for years the stamp would still be there i will say it this is a deralition of duty by all the gypsum floor layers using tilers as test dummys well we have put a man on the moon but its to much to ask that they stamp there work just what have they got to hide may be they dont now what there doing or dont know what there using on a day to day basis they should be ashamed of there i am all wright jack atrtude its all write ive been paid what do i care for the client or tile fixers after all just got another wod shame of the building trade and you should be ashamed you stink

 

[Spud]

It a mine field at the moment with too many calcium products each with very specific characteristics and each require particular prep work in Europe this simply doesn't apply as the screeners have to prep their floor for tilers

 

[beanz]

Because there is often very fine dust on the surface of these screeds which can interfere with the penetration of primers. Also the screed has been in a construction site for a number of weeks or months and will have surface contamination from extraneous materials e.g. Mud, plaster, mortar, paint etc etc. Also the surface of these screeds can be very hard and very dense which further interferes with the penetration of primers. Sanding opens the surface texture and subsequently provides a mechanical key for said primers etc. it also opens the surface to promote faster drying. I can obviously only offer guidance based on experience and the national and industry best practice codes. It may be that if you tile it you would get away with it and it would not fail. But, if it does, you would stand alone in sorting it out because the first questions you would be asked would include "did you sand the screed as per the instructions of the tiling association guide to tiling to calcium sulphate screeds and as per the instructions on pretty much every bag of tile adhesive in relation to these screeds" I know that is what I would ask....


sanding is is not just to remove Laitance but is to prepare the screed to receive bonded floor coverings...

Giving it a key by hand would suffice for all but the laitance (which may or may not be an issue, as it isn't loose!?!) here. When speaking to Ardex tech about this particular type of screed, they didn't even mention sanding. All they asked was whether the screed takes water, or if it just sits on top. They said if the screed takes the water, you can prime it with an Acrylic primer at 3:1.

 

[beanz]

It a mine field at the moment with too many calcium products each with very specific characteristics and each require particular prep work in Europe this simply doesn't apply as the screeners have to prep their floor for tilers

Which if you listened to the screeder that layed the floor we did a few weeks back, would've consisted of a sweep with a stiff broom.... Lol

 

[Rizzle from the Portizzle]

they run away and run away why ?we stand by our work again and again but where are they to be seen spending there cash and not giving a toss what they leave behind reminds you of our bankers no shame or guilt over who pics up the damamage after all they have there money and are well gone never in building trade have i ever come across a buntch of i realy dont care about my work just the money i make and sod those who follow if you cant stand by your work or leave your mark you are worthless like all of these screed what do they need to hide ? why cant they stamp them are they so ashamed by what they do they should be whats so wrong in saying i did that makes you wonder why they hide the fact of what they laid are they ashamed of what they are doing and dont want anybody to know what they are up to no confedenes in what they are doing if they own up to it well put your stamp if you have one once of honestey between you if not we realy know why and pass that info on to our clients we believe they should only buy products they can trust and not ones who are ashamed to say we did that?

 

[beanz]

I'm not sure about the stamping.. Nobody else in the building trade stamps their work!?! And I don't think you can really lump all screeders together. At least Alan's on here trying to shed some light on the subject.

 

[Ajax123]

It a mine field at the moment with too many calcium products each with very specific characteristics and each require particular prep work in Europe this simply doesn't apply as the screeners have to prep their floor for tilers

But Gary, the prep requirements all calcium sulphate screeds are all the same. In fact if you look at the requirements for the contract flooring association the requirements for all screeds is the same full stop. The only thing that changes is GHD need if not for a primer which is dictated not by the screed but by the adhesive.. I agree in Europe a lot of screeders do the prep but that us primarily because most of the also tile the floors as part of thief artisan contract... Certainly in France and holland anyway.

 

[Ajax123]

they run away and run away why ?we stand by our work again and again but where are they to be seen spending there cash and not giving a toss what they leave behind reminds you of our bankers no shame or guilt over who pics up the damamage after all they have there money and are well gone never in building trade have i ever come across a buntch of i realy dont care about my work just the money i make and sod those who follow if you cant stand by your work or leave your mark you are worthless like all of these screed what do they need to hide ? why cant they stamp them are they so ashamed by what they do they should be whats so wrong in saying i did that makes you wonder why they hide the fact of what they laid are they ashamed of what they are doing and dont want anybody to know what they are up to no confedenes in what they are doing if they own up to it well put your stamp if you have one once of honestey between you if not we realy know why and pass that info on to our clients we believe they should only buy products they can trust and not ones who are ashamed to say we did that?

I wasn't going to grace this with a comment but felt as you have mentioned it twice you wanted a response. Please stop drawing ridiculously over dramatised and generalised inferences from the fact that screeders don't "stamp" their work. Conspiracy theories about what they have to hide are unhelpful and frankly a big silly. Most screeders like most tilers are solid professional tradesmen. Most of them leave information with sites about the screeds they supply. You should perhaps analyse why this information is not passed on. There are some who are less capable just as there are tilers who are less so but generally no one goes out to work to do a bad job and they certainly don't do it to p**s the tiler off. In fact I would suggest that the vast majority of screeds go in before the decision on what coverings are used us made so the reeder probably doesnpt even know tiles will be used... Or even care.... Why should he...he is a screeder not a tiler. That's your job.

To make these sorts of issues disappear we could of course begin encouraging screeders to take on the tiling as well but that would eat into your work wouldn't it....

 

[CJ]

These newer pumped screeds that look like Sand/cement screeds? Is there a way of telling, because not all customers actually know themselves.
They get a building contractor in, then when at roof level they are gone, and the customer phones us.

 

[Ajax123]

These newer pumped screeds that look like Sand/cement screeds? Is there a way of telling, because not all customers actually know themselves.
They get a building contractor in, then when at roof level they are gone, and the customer phones us.

You can usually find out if you ask the questions e.g. Who installed it, who supplied it, was it pumped, how deep is it etc etc. if you really draw a blank on this my advice is treat it as if it is calcium sulphate anyway because generally speaking whatever you do with anhydrite will work on other screed types perfectly well.