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Priming Anhydrous Screeds - Working Out If Primers Are Equivalent?


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#1 cjard

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Posted 23 April 2016 - 05:44 AM

For the house I have vinyl planks, requiring use of f ball p121 primer or similar. For the conservatory I have tiles and apparently use of something like weber pr360 is recommended to stop the cement in the tile adh reacting with the gypsum in the screed

Both p121 and pr360 are acrylate suspensions, but are they the same thing? Is there an easy way to check? Ingredients aren't published, and the SDS doesn't help in this case.. I ask because pr360 is twice the price, so it'd be nice to know if it's the same stuff!

Edited by cjard, 23 April 2016 - 05:44 AM.


#2 Nickfromwales

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Posted 23 April 2016 - 10:41 AM

From everything I've seen come up off liquid screeds, is say nothing will stick to them. Adhesion is the problem, reaction is an after concern.
Hire a professional grinding / extraction setup and get rid of the surface 'scum' layer and then look at what is compatible.
It's likely that most flexible primers are suitable to use after that has been done.
Regards, Nick

#3 Woodgnome

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Posted 23 April 2016 - 02:01 PM

They do a tile adhesive for these screeds called Anhyfix. Made by Tilemaster.

#4 Nickfromwales

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Posted 24 April 2016 - 10:20 AM

Best reading the small print on the back of the bags ;)
I saw those adhesives too and thought "happy days" until I read that the mechanical abrasive prep work is STILL required.
There's no short cut here folks :(
Regards, Nick.

Edited by Nickfromwales, 24 April 2016 - 10:20 AM.


#5 windsurf21

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Posted 24 April 2016 - 11:20 AM

I've been working on a large project, 200sq/m of anhydrite screed, ufh, limestone flooring.
The screed supplier states, a week after pouring the laitance can be removed and with the use of ditra mat tiling can commence. The guy that did the pour actually said "just a stiff brush"!
Norcros technical specified that until the screed is fully cured, laitance will keep forming.
Then mechanical removal of the laitance.
Primed with progressively stronger coats of primer, until completely sealed.
Then tile.
(They wouldn't comment on the use of an uncoupling mat!)
I do have the spec sheet from both company's if needed.


#6 cjard

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Posted 24 April 2016 - 01:11 PM

Fortunately(?), the speed that my build progresses, the screed has been down for about 6 months. What I do find amazing is that even now, if I leave a bucket, box, tool bag, roll of wool etc on it for a week, there will be a damp looking patch the shape of the object when I lift it up. I'll be running the heating for a month and doing a moisture test first, before flooring. I'll also be looking at hiring a floor sander to remove the laitence. I imagiine a normal build with a schedule Joe Bloggs might expect sees a client seeking a screed be tiled before it's really dry

One thing to remember with these screeds is that they're like a sponge.. The "damp" is most prominent in rooms where the plasterer has flicked water around, it just soaks into the screed and spreads out, drying slowly. Can't help but think that one of the problems with the screed is that tile adhesive contains water, some of which is used in the reaction that sets it, the surplus can't dry out quickly due to the imperviousness of the covering so where else can it go except for into the screed, or sit forever preventing full adhesion.. Probably the only way round this one is to use a non water based adhesive?

#7 Nickfromwales

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Posted 24 April 2016 - 07:00 PM

I think a good 30 days after tiling with cementitious adhesive and THEN grout imo. I'd run the Ufh gently after 7 days and then give it 12 hours on 12 hours off daily until the 30 days expires.
After that it should be bombproof.
:ph34r:

#8 Woodgnome

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Posted 25 April 2016 - 04:02 PM

View PostNickfromwales, on 24 April 2016 - 10:20 AM, said:

Best reading the small print on the back of the bags ;)
I saw those adhesives too and thought "happy days" until I read that the mechanical abrasive prep work is STILL required.
There's no short cut here folks :(
Regards, Nick.

Yep, I know. But it saves the hassle of what primer to use and how many coats etc..

#9 Woodgnome

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Posted 25 April 2016 - 04:03 PM

View Postwindsurf21, on 24 April 2016 - 11:20 AM, said:

I've been working on a large project, 200sq/m of anhydrite screed, ufh, limestone flooring.
The screed supplier states, a week after pouring the laitance can be removed and with the use of ditra mat tiling can commence. The guy that did the pour actually said "just a stiff brush"!
Norcros technical specified that until the screed is fully cured, laitance will keep forming.
Then mechanical removal of the laitance.
Primed with progressively stronger coats of primer, until completely sealed.
Then tile.
(They wouldn't comment on the use of an uncoupling mat!)
I do have the spec sheet from both company's if needed.
Would be interested in seeing the spec sheets.
Ta.
What do they say regarding use of Anhyfix and the need to prime?

#10 Nickfromwales

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Posted 25 April 2016 - 04:28 PM

Page 1
http://www.xyoneconn...FixTechData.pdf
;)

#11 Woodgnome

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Posted 25 April 2016 - 04:59 PM

Ta. So it may well pay to use ordinary adhesive and prime as the Anhydix only comes in Rapid set I think. No idea of cost comparison.
I'm going to go for Anhydrate screed I think......or maybe not...

#12 Nickfromwales

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Posted 25 April 2016 - 05:08 PM

Dry screed for me every time. Why create all the extra problems for yourself? Life's tough enough as it is ;)
Where are you? My screener travels and can give you a supply and fit price, and has done for one other member here already iirc.
Observe expansion joints as always, whichever you choose.
Regards, Nick.

#13 Onoff

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Posted 25 April 2016 - 08:11 PM

View PostNickfromwales, on 25 April 2016 - 05:08 PM, said:

Dry screed for me every time.

Wet concrete / dry screed.....doesn't matter a carrot when you leave your notebook under it with ALL your handwritten notes and measurements! :lol:

.....possibly, it could still turn up!

#14 Nickfromwales

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Posted 25 April 2016 - 08:30 PM

That's gotta hurt. :(
The only thing that saves the day there is the photos you take as you go along.
You have taken loads of photos ? Haven't you?
:unsure:

#15 Woodgnome

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Posted 25 April 2016 - 08:47 PM

View PostNickfromwales, on 25 April 2016 - 05:08 PM, said:

Dry screed for me every time. Why create all the extra problems for yourself? Life's tough enough as it is ;)
Where are you? My screener travels and can give you a supply and fit price, and has done for one other member here already iirc.
Observe expansion joints as always, whichever you choose.
Regards, Nick.
Nick, I'm in North Devon, maybe a bit far for him?

#16 Nickfromwales

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Posted 25 April 2016 - 09:17 PM

View PostWoodgnome, on 25 April 2016 - 08:47 PM, said:


Nick, I'm in North Devon, maybe a bit far for him?
He's gone much further than that.
Would you like me to ask?
:)

#17 Woodgnome

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Posted 25 April 2016 - 10:40 PM

View PostNickfromwales, on 25 April 2016 - 09:17 PM, said:

He's gone much further than that.
Would you like me to ask?
:)

Yep, ask away. Approx 100sqm @ 75-80mm. No pipework as its already in the slab. ....Soon as.... :(
Cheers....

#18 Woodgnome

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Posted 27 April 2016 - 10:03 PM

Nick, have you had a chance to ask your bloke regarding the screed price?
Cheers.

#19 Nickfromwales

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Posted 27 April 2016 - 10:12 PM

I would have if it wasn't for the swiss cheese that has temporarily replaced my brain.
I'll buzz him in the morning for you. If he's up for it I'll pm you his mobile number. He's mustard. :)
Regards, Nick.

#20 windsurf21

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Posted 27 April 2016 - 11:10 PM

Here's the spec sheet from the screed supplier.
I'll search through my emails and find the discussion I had with Norcros.
I also got the opinion of a third party, who didn't agree with norcros that more laitence would form after the initial drying. And stated that the adhesive manufacturers need to get their s#*t together with these screeds as they all seem to have a different opinion.
FWIW, I removed all laitance, primed 3 coats with an acrylic primer, the last of which was near enough neat. Fixed ditra mat with rapid cementitious adhesive. Then fixed the limestone with rapid cementitious adhesive.
The first phase was completed before Christmas, I was there briefly last week to check up on phase 2, and it all seems OK.
The UFH has been running now too.

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