anhydrite ??

[davebates]

hi guys what is anhydrite screed and what is the laitance that will need to be removed from it ??? in order to use a slc ???

[Dave]

Hi Dave..

Anhydrite is a gypsum based product... why would you need to SLC a flowing screed.

[davebates]

I was looking at the mapei slc's because i need to level a conservatory floor prior to underfloor matting and tiles, and it mentioned the above anhydrite screed needing the laitance removed before using there product. Im guessing it will be concrete in the conservatory but didnt know what anhydrite was or the laitance there on about.

[Dave]

Ah right, then you are fine..

Click the search box top right and type in Anhydrite, you will get loads of info for future reference.

[davebates]

cheers

[davebates]

just another quickie if i were to come across this type of screed how would it differ from concrete(looks wise) not seen it before would be of a pinkish colour ?? like plaster ??

[Dave]

No..lol..

Most are very light in colour ... towards a cream in colour but others can look grey.. the best to check is ask the customer... but info like this is here.. http://www.tilersforums.co.uk/search...earchid=580143

[nybor62]

the last few ive done have been creamy in colour, when you see one i think you will know its so obvious its not concrete

[davebates]

cheers guys, i cant get that link to work though

[Dave]

works ok for me but if you do the search then you will get the same anyway..
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[Ajax123]

as the anhydrite is Gypsum Based you would be better using a gypsum based SLC on it. Would give a better heat output I would think as well.

[Dave]

Alan, read the post..

[Ajax123]

Alan, read the post..

Oops!. Cement better on concrete.........

Laitance is the finer particles which float to the surface of the screed and form a loose surface skin. Lots of anhydrite screeds no longer have this though. If in doubt....ask the manufacturers. the other bits seem covered already.

[diamondtiling]

All the apartments that we are tiling have anhydrite screeds, getting some of the tilers to prep properly was a nightmare at first, we have also had at least 20 floors fail (before tiling) they were very crumbly and had a lot of bounce in them? That required a full removal including the water fed UFH and replacement at the screeders cost. Ouch!!!

[Rich]

Im glad Im not paying for that!!

Alan mentioned a gypsum based SLC, the last anhydrite screed I did was unbelievably bad, it had more shape to it that most bad sand and cement screeds I do!

Has anybody used the gypsum SLCs? What are they like to work with? Who can we get them through?

I used the Weber gypsum adhesive and was very impressed with it, do weber do one?

This is all for future reference, might just save me a lot of trouble later on

[Ajax123]

Weber do one, as do Forbo Flooring, PCI, Creative Impresions, Bostik and Uzin.

I have used the Uzin and the Bostik ones myself and they were both easy to work with.