Failed anhydrite floor

[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