Failed anhydrite floor

[Ajax123]

Anhydrite screeds are made in ready mix facilities where they are subjected to quality assurance regimes. The sand used is specially selected and tested for suitability by the binder manufacturers (us). The measure of sand quality is usually determined by how quickly the screed hardens. Ergo you will prove that the sand is of good quality and suitable for inclusion in the screed by doing such a test. We already know the answer before the screed is made. Same with the binder. It is unusual in the extreme for there to be anything aims with the individual components of the screed such that standard statistical process control will take care of things. Add the sand and binder together with water and you have a screed mortar. There really isn't much to go wrong during the manufacturing process itself.

Most of the issues with screeds of all types are caused not by the screed itself but what people do with it and how they do it....

 

[the diving tile]

Most of the issues with screeds of all types are caused not by the screed itself but what people do with it and how they do it....

Thanks for that , is there any type of pourable floor that does not need sanding and sealing

 

[Ajax123]

Thanks for that , is there any type of pourable floor that does not need sanding and sealing

All screeds should be lightly abraded before applying bonded floor coverings. As for sealing it depends more on the adhesives. Some don't require a primer some do. ALL adhesives based on Portland cement will require a suitable (ideally epoxy) primer.

 

[Dougs Third Go]

from purely a tilers perspective, gypsum threads certainly seem to throw up more problems than solutions, we only seem to get answers ipso facto, ie, latching the stable door after horse has bolted. Alan this is no disrespect to you whatsoever, alone, you have stood your ground and tried to explain, at bloody long length, the merits of anhydrite, but personally the only people I can see benefitting are builders looking for a quick screed.. I'm in the minority have now (having the "know how" now) as to how to prepare and test for a anhydrite screed, but Cap'n Quick and Cheerful, down the road from me will only be to willing to tell customers that I'm talking a load of garbage and he'll do it for half the price....need I add more?

 

[DHTiling]

The only bad thing about calcium screeds is a tiler who does not make sure he/she stands their ground and insist it is dry and prepped correctly , the rest is down to the tiler , get to know the correct way with your chosen adhesive etc..

Simple as that , learn to tile to them successfully or get left behind , blunt but true .

 

[Ajax123]

from purely a tilers perspective, gypsum threads certainly seem to throw up more problems than solutions, we only seem to get answers ipso facto, ie, latching the stable door after horse has bolted. Alan this is no disrespect to you whatsoever, alone, you have stood your ground and tried to explain, at bloody long length, the merits of anhydrite, but personally the only people I can see benefitting are builders looking for a quick screed.. I'm in the minority have now (having the "know how" now) as to how to prepare and test for a anhydrite screed, but Cap'n Quick and Cheerful, down the road from me will only be to willing to tell customers that I'm talking a load of garbage and he'll do it for half the price....need I add more?

I ain't gonna give up.... They'll neverrrr tak ooor freedom.... And all that.

To be fair though I have seen step changes for the better over the 10 years or so I've been dealing with these screeds and things are probably a million times better than they were when I joined the forums.

 

[The Legend; Phil Hobson RIP]

I always ask the question "what type of screed is this?" after attending Alan's course in Durham, I realize how hard it is to distinguish the anhydrite from sand and cement just by looking at them.

I think the key is to find out who laid the screed, and what is it?

 

[Ian]

I always ask the question "what type of screed is this?" after attending Alan's course in Durham, I realize how hard it is to distinguish the anhydrite from sand and cement just by looking at them.

I think the key is to find out who laid the screed, and what is it?

I always ask now, even if I think I know what it is. Anhydrite is normally easy to spot with all the foam barriers around the perimeter. It has a yellowish colour as well.

 

[Dougs Third Go]

I always ask the question "what type of screed is this?" after attending Alan's course in Durham, I realize how hard it is to distinguish the anhydrite from sand and cement just by looking at them.

I think the key is to find out who laid the screed, and what is it?

as do I Phil, but most, won't ask as they've never heard of it, thus just assume it's normal concrete screed, and the rest, as they say, is history

 

[Dougs Third Go]

I always ask now, even if I think I know what it is. Anhydrite is normally easy to spot with all the foam barriers around the perimeter. It has a yellowish colour as well.

Bri, that's a given with a concrete screed, ie perimeter expansion joint.

 

[the diving tile]

Hemi hydrate Floor Screed have being told that this one can be tiled on without any sanding or priming can you shed any light on this

 

[DHTiling]

Hemi hydrate Floor Screed have being told that this one can be tiled on without any sanding or priming can you shed any light on this

What about surface contamination from other trades ? Dirty screeds are a mare .

 

[John Benton]

Alan - brilliant advice, your knowledge seems to have no boundaries, any chance of the 6 numbers tomorrow night?

Did you manage to catch the pictures of mine as 2 threads were combined regarding failed floors?

 

[Ajax123]

Hemi hydrate Floor Screed have being told that this one can be tiled on without any sanding or priming can you shed any light on this

Yes it's wrong.....

 

[beanz]

Yes it's wrong.....

Am I right in thinking this is a very low laitence floor? What would your advice be to prep this? And why are there so many of these pourable screeds!?!?!

 

[Ajax123]

Am I right in thinking this is a very low laitence floor? What would your advice be to prep this? And why are there so many of these pourable screeds!?!?!

You need to stop thinking low Laitance / high Laitance. The simple fact is that all screeds produce Laitance to some degree. The advice of the contract flooring association, the tiling association, the vast majority of the adhesive and tile suppliers and manufacturers is that the screed should be lightly abraded eg sanded to remove Laitance and other contamination likely to affect adhesion and to promote a key for primers and adhesives.

This advice extends not only to calcium sulphate screeds of all types, powerfloated concrete and close textured sand cement and pourable cement based screeds.

Now then. If the screed manufacturer (or in this instance I know it is the binder manufacturer) who bear in mind is removed from the contract process for laying the tiles, says "you don't need to sand this screed as it is a hemi hydrate" firstly that flies in the face of the advice of the floor covering specialists advice and secondly if the tiles fail and you have not sanded the screed when the adhesive supplier and the tiling association and the primer manufacturer and the contract flooring association and all of the independent experts that will come your way to find the cause of the failure what do you think wil be the first question you are asked. It will be "did you sand the floor" and then when you say no because the binder supplier said I didn't need to, do you think the binder manufacturer is going to stand beside you and provide you with expert support to prove all of the other experts are incorrect.... I will let you answer that one yourself.

the rules are simple, sand the screed!?!!?!

therea re so many of these screeds about because people who use them recognise the advantages that they offer. They do not choose their screed based on how comfortable the tiler is in putting tiles down. Learn to tile them properly and you won't have to feel uncomfortable.

 

[beanz]

I'm only asking because I sanded one of these screeds, after the screeder said it wasn't necessary, and couldn't see what I was taking off!?!

 

[Ian]

I've finally got round to starting this one, here's a couple of pics from removing a tile. It seems to me that the screed wasn't sanded as the laitence is on the underside of the tile and adhesive. The whole floor is going to have to come up (70m+), so a costly mistake for the developer. The adhesive is stuck fast to the tile so they aren't reusable on this job, I might possibly offer him a few quid and take a load to do my patio with :lol: I'll fix them with sand and cement so the adhesive on the rear shouldn't be a problem. I'll see what I think when I've removed them all.

 

[White Room]

Those tile will look nice on a patio but your'll need a small lorry to carry them away....

 

[Ian]

Those tile will look nice on a patio but your'll need a small lorry to carry them away....

I only need 40m, should be able to do it in the van in a couple of trips.

 

[widler]

Would the sand and cement bed stick it the anyl addy stuck on the tile bri ?

 

[Ian]

Would the sand and cement bed stick it the anyl addy stuck on the tile bri ?

Well that did cross my mind, I reckon an SBR/cement slurry coat would sort it out. Only one way to find out! I'll let you know how I get on!

 

[widler]

To be fair mate ,it probably be fine , they say you can use if on s/c screed as long as primed right.
They say you can't use gypsum products on s/c but you can skim s/c render it with gypsum finish,go figure

 

[Ian]

Like you say mate, it's all in the priming. I'll find something that'll stick to it, a slurry coat is the best bet I reckon.

 

[widler]

Aye,or you could drill and plug in it each corner