Calcium sulphate screed preperation

[area tiling]

this will be my first time fixing porcelain 900 x 900 tiles onto a calcium poured screed , with under floor heating , the screed was laid in feb and is getting tested next week by the screed contractors!
now my main concerns is getting the prep work correct -
*floors are completely dry
*remove latience by sanding , they hoover
* prime with acrylic primer twice in opposite directions to each coat
* fix tiles with flexible fast set
* lay expansion joints

this may seem a bit strange but what does the latience product look like , is it flakey sand particles or a limescale product?
Any advice would be welcomed ! Thanks

 

[Ian]

What adhesive are you using?

 

[Gazzer]

When sanded , the laitance will be a very fine powder.

 

[area tiling]

What adhesive are you using?

Weber

 

[Ian]

Weber

Can I recommend that you use anhyfix from tilemaster, it is an amazing product. I've used it on about 160 m2 now and can't recommend it highly enough.

 

[bugs183]

As Bri says Area go for a gypsum compatible adhesive here, there are too many issues that can arise with cement based adhesives. Lots of threads on here about these screeds if you look.

 

[Ajax123]

Dont know if Anhyfix is available in Ireland but if not I know gypfix from nicobond is and also I am fairly sure Norcross have one over there. Nothing intrinsically wrong with the weber system as long as everything is done perfectly but as you appear to have little or no experience of these screeds I would suggest that you need to build in a much robustness as possible and that means avoiding cement based adhesives IMO.

In terms of preparation have a look at the attached data sheets which might help

http://www.gypsol.co.uk/6_Post_Installation.pdf
http://www.gypsol.co.uk/7_Floor_Finishes_Flowchart.pdf
http://www.gypsol.co.uk/11_Ancillary_Products.pdf

 

[area tiling]

What's my best option in Removing the laitance material from the screed , a floor sander , planner or grinder baring in mind its 210 m2 ! And if I use a calcium sulphate adhesive will I have to remove the latience!

 

[Stef]

What's my best option in Removing the laitance material from the screed , a floor sander , planner or grinder baring in mind its 210 m2 ! And if I use a calcium sulphate adhesive will I have to remove the latience!

Use a floor sander.
Even if your addy is gypsum compatible you still have to remove the laitance.
Try & use a water based epoxy primer, that's what I was advised but I used TileMaster PrimePlus & AnhyFix & I'm hoping I don't have issues with it..

 

[Ajax123]

You only need epoxy primer if your adhesive Is chemically incompatible. Epoxy will inhibit the migration of moisture borne sulphites in the screed so will prevent any adverse chemical reaction. If you use a gypsum compatible adhesive an acrylic primer is perfectly acceptable.

The system you have used stef is fine.

 

[Gazzer]

Use a floor sander.
Even if your addy is gypsum compatible you still have to remove the laitance.
Try & use a water based epoxy primer, that's what I was advised but I used TileMaster PrimePlus & AnhyFix & I'm hoping I don't have issues with it..

I am still looking for a decent (affordable) sander for these floors. I use a large Makita belt sander at themoment but its slow work.

 

[Stef]

I am still looking for a decent (affordable) sander for these floors. I use a large Makita belt sander at themoment but its slow work.

I was having a look for one a few weeks ago, they are an expensive bit of kit.
Think I will stick to hiring one if I ever need it.

 

[Ajax123]

I am still looking for a decent (affordable) sander for these floors. I use a large Makita belt sander at themoment but its slow work.

Is it not cheaper to hire or are you starting to see these floors more and more often now.

 

[Gazzer]

Well I guess after about 10 floors the hire costs could have gone towards a purchase plus you need to arrange to collect the machine and thats time off work etc. I prefer to buy.
I do have an old floor polisher which I hope could have been adapted and alsoI was looking at the Hiretech HT8 and HT7 but wasnt sure if they were man enough for the job.

 

[Ajax123]

Would think something like this would be better. I will check with some of hitherto screeners what they use and get some price guidance for you.

http://www.spe-int.com/multipurpose...se-preparation-system.aspx?prid=19&cid=4&p=41