temp of calcium screed before tiling

[kevinz3]

hi
anyone tell me what the procedure is before tiling on to cal/sulp screed with underfloor , do i turn heating off before tiling or leave it at 10 degrees any info would be much appreciated

 

[Sean SML Tiling]

Remove latiance
Commission ufh
Once commissioned then screed should be 75%rh before tiling
Ufh should be turned off 24hrs before tiling

 

[kevinz3]

hi
thanks for info , just a few more to ask, 1 , how many coats of primer should i put on screed?, 2 what is the best material to be shower tray down on to screed? and 3 joiner has fitted certified marine ply to shower walls , is that a no no and should i change it to aqua panel ?, thanks again

 

[Ajax123]

As above other than we always recommend turn the heating off 48 hours before doing a moisture test the tiling if dry.

 

[Perry]

Joiner has fitted certified marine ply. Well he should be certified then. :ban:

 

[kevinz3]

hi
thanks for that but not helpful

 

[J Sid]

Surprised they haven't ask the chippy to do the tiling as well

 

[kevinz3]

anyone got some constructive info please

 

[Ian]

What adhesive are you using on the screed? With regards to the shower, I wouldn't tile onto ply in a shower area, either tank it first or replace with Aqua panel or similar.

 

[kevinz3]

hi
thanks, i am using keraquick on floor with latex added , just need to ask how many coats primer g it needs, would the ply be ok with a waterproof coat then , and what would be best to use

 

[Stef]

As Bri asks, what adhesive are you using?
I would be using a gypsum compatible addy, AnhyFix being my preferred choice.
One coat of TileMaster primer plus diluted 4:1 is what I've found best.

 

[Ian]

As Bri asks, what adhesive are you using?
I would be using a gypsum compatible addy, AnhyFix being my preferred choice.
One coat of TileMaster primer plus diluted 4:1 is what I've found best.

Ditto. In my humble opinion a gypsum based adhesive is the only way to go, I wouldn't even consider anything else.

 

[Stef]

Ditto. In my humble opinion a gypsum based adhesive is the only way to go, I wouldn't even consider anything else.

I used Bal rapid set a couple of weeks ago to push a job on, 6 coats of primer till it stopped soaking in to the screed.
Time will tell but the tiles seem well fixed.

 

[kevinz3]

hi
thanks, i am using mapei keraquick on floor with latex added , just need to ask how many coats primer g it needs, would the ply be ok with a waterproof coat then , and what would be best to use

 

[Ian]

Couldn't tell you about the primer, it'll perhaps say on the bottle, if not, ring mapei technical. With regards to the tanking, I think I'd choose ardex wpc over ply.

 

[stusgsx]

Why are you using keraquick?
Take away the risk and use gypsum based as others have said

 

[kevinz3]

i called them and they said as long as you mix in the latex additive it makes it to an s2 adhesive , but looking at your replies what other adhesive is best then

 

[Ian]

Anhyfix from Tilemaster, it's the holy grail of adhesives for gypsum screeds.

 

[kevinz3]

called mapei technical and they confirm as long as its sealed with primer and all latience removed should be no issues as even some gypsum based adhesive still need primer and so defeats the object of being a special adhesive so still not sure

 

[Ian]

So you're asking for advice and going to do what you want anyway. You've been told what's best, up to you whether you take the advice or not.

 

[J Sid]

If they told me it "SHOULD be OK" I would not use it.
I need to hear "It WILL be OK"

 

[kevinz3]

hi
no i am not going to go ahead without advice , my point was they said the surface needs to be primed to stop it coming in to contact with the screed and also said specific adhesives also need to be primed as well so the issue is the screed does not contaminate the adhesive , but why if its specific to calcium sulphate then why prime, thats all i said , if the forum is about advice etc then thats the whole point of asking is it not

 

[Sean SML Tiling]

Gypsum adhesive doesn't need to be primed as it's gypsum to gypsum. Cement adhesive needs to be primed or it will cause a chemical reaction and Debond. what happens if you trowel the floor and you damage the primer? You going to scrape the adhesive back re prime wait for it to dry then try to trowel again?

 

[Ian]

The primer should be soaking into the screed not sitting ontop (when using gypsum adhesive), the reason for a primer is really only to stop the screed drawing the moisture out of the adhesive so quickly. Yes it will seal the surface but, the adhesive will still be sticking to the screed. In the case of a cement based adhesive, the primer will be creating a barrier to stop any unwanted reaction.

 

[kevinz3]

thanks for info , so primed or no prime then if using gypsum add?? conflicting advice