The best primer and Adhesive for anhydrite screed

[Jase-tiler]

Hi, I have a 60sqm floor to lay on Anhydrite screed, I am using 800mm x 800mm porcelain tiles and Ditra matting.
What is the best primer to use, and adhesive to fix Ditra matting.
And finally what is the best adhesive to bed the tile with.
[h=1][/h]

 

[Ajax123]

Use an anhydrite compatible adhesive. Here's a list of manufacturers, although it's not exhaustive, and the primer from the same manufacturer to fix the ditra. On top of it you can use your usual flexible cement based adhesive. Also a flowchart that helps you ensure all the steps are followed

Broken Link Removed

[DLMURL]http://gypsol.co.uk/media/1170/guide-sheet-4-flooring-flowchart.pdf[/DLMURL]

Don't forget you might need a movement joint or two in an area that big.

ring me if you need any other advice 07966651006

 

[Sean SML Tiling]

I've just finished an anhydrite screed and I used tiles master anhyfix with their prime plus. I'd reccomend anhyfix to fix ditra then use time master setaflex (slowset) to fix the tiles to ditra.

 

[widler]

Same as Sean, to the letter

 

[Ajax123]

I'm not supposed advertise specifics but I was I would say the same...

 

[Jase-tiler]

Thanks for the advice I will follow it.
Also what is the process involved installing a movement joint?

 

[Stef]

I've done quite a few anhydrite screeds now & everyone I've done I've used TileMaster AnhyFix.
I've not fitted Ditra on top but if I was I would be using the exact same process as above.
If there's a movement join in the substrate then follow that through the tiles, either fit a movement join or do it yourself.

 

[Sean SML Tiling]

Stefs do you ever leave grout line out and silicone it to allow more expansion

 

[Stef]

I've only ever done it once on an anhydrite screed, had to break it over the door threshold as it was showing a very small crack & didn't want to take the risk.
I would pick a calcium sulphate screed over any other now as there's no hassle tiling to them.

 

[Stef]

Meant to say, it's funny how quick you get used to these screeds.
Looked at a job last week, 4 floors, 2 downstairs on top of a Gyvlon screed.
Speaking to the builder & he was convinced it was a cement based screed till I showed him what needs done to it.
I think he was a but dubious what I was telling him, got a phone call a few days later to say that everything I had told him was exactly what the screed guy told him.
Only problem I picked up was that the screed guy told him it was 1mm per day drying time, I had to explain that that information only goes to 40mm then it's 1mm every 2 days.

 

[Ajax123]

You will rarely see movement joints in anhydrite. However if the tile face needs a joint e.g. Large bays, door thresholds, etc this these should be installed regardless of whether or not you see a joint in the screed. Sometimes the joints are not required in the screed and sometimes they are just beneath the surface of the screed so you can't see them. Not ideal I know but it is the best way for the screeders.

 

[Stef]

Alan, I actually quoted you to the builder & was going to pass on your number to him as I knew you would verify what I was explaining to him.
Thankfully it never got to that stage as I know him & he knows what I'm like when it comes to anything tile related.

 

[Sean SML Tiling]

You will rarely see movement joints in anhydrite. However if the tile face needs a joint e.g. Large bays, door thresholds, etc this these should be installed regardless of whether or not you see a joint in the screed. Sometimes the joints are not required in the screed and sometimes they are just beneath the surface of the screed so you can't see them. Not ideal I know but it is the best way for the screeders.

When separating the floors in bays is it ok to use a 3mm silicone joint as a movement joint?

 

[Ajax123]

When separating the floors in bays is it ok to use a 3mm silicone joint as a movement joint?

Yes that's ok provided the floor doesn't expand by. More than about 2mm. Movement joints though are usually 5mm in my experience

 

[Sean SML Tiling]

Ok on anhydrite screed 80mts and I've separated the floor 6 bays as there is 6 uhf zones. Customer didn't want industrial joints and went for silicone.

 

[Ajax123]

Ok on anhydrite screed 80mts and I've separated the floor 6 bays as there is 6 uhf zones. Customer didn't want industrial joints and went for silicone.

The screed itself hardly moves so that bit will be fine. Can't say for the tiles though.

 

[Dave]

That size of movement/expansion joint isn't suitable for floor Installations imho .. But I have seen it done , might work for small areas with a joint in a doorway , min I would install for neatness is 5mm cold joint or larger areas , a preformed 10mm joint.

 

[newlineuk]

Do you guy's grind the laitance off first?

 

[Ajax123]

Do you guy's grind the laitance off first?

If you don't you ain't doing it right... :mad2:

 

[Stef]

As Alan (Ajax) says, you must remove the laitance or the floor will fail!!!

 

[J&K]

We have an Anhydrite screed floor laid last July and tiled in October. Screed depth 70-75mm. We tiled the floor before the UFH was commissioned, which reading this thread was our (expensive) mistake. The tiles have de-bonded from the floor and we have last weekend taken up 75sq m of 800x800mm porcelain tiles, salvaging about 50%. Inspecting the adhesive the primer is attached to it, so the primer has separated from the screed. We scraped the floor twice to remove the shiny top appearance, at 90 deg for each pass. This presumably was to remove the laitance? I assume there must have been trapped mositure that casued the de-bonding?
The average thickness of the adhesive is 20mm, and on one small area where we laid some levelling compound it has not de-bonded.
The UFH has been on during the winter for several days and for a week since removing the tiles. It must now be moisture free.
Having reordered replacement tiles, I would appreciate advice on what process to now follow in relaying the them.
I have read we should remove laitance which I assume is the top of the screed. How do we do this effectively?
Then should we use a Ditra type matting now that the floor is completely dry?
If no matting is recommended and we need 20mm of adhesive to bring the tile to the correct level height, should we use the Tile Master AnhyFix only, or can we use a rapid set flexible adhesive?
Appreciate any advice that can be given.

 

[newlineuk]

If you don't you ain't doing it right... :mad2:

Just checking.....

 

[Sean SML Tiling]

Did you do a moisture test before starting?

 

[Tile seller]

A standard anhydrite screed at 75mm would take 110 days to dry fully, (5 months), but depends on what was used.

Also, what primer did you use, did you dilute it and how many coats did you give it? Also what adhesive?

Did you follow the correct procedures for turning on the ufh?

Sorry for all the questions,just trying to see what went wrong so you don't get a repeat

 

[Sean SML Tiling]

I just finished a anhydrite floor and I got the customer to sign that the floor has been sanded then hovered then primed correctly to the manufacturer and gypsum adhesive was used. He also signed that 5 meter readings was done and that all 5 was below British standards 75% rh.

 

[Lee@emctiles]

[MENTION=45072]J&K[/MENTION] TileMaster also do a Anhydrite Leveller that may be an option for you to bring floor up to level?

http://www.tilemasteradhesives.co.uk/anhylevel

you might want to read relevant data sheets ect on Anhyfix as well http://www.tilemasteradhesives.co.uk/anhyfix

 

[Turkish tiler]

I think Kerakoll ....... Does best primer and adhesive for pump screed

 

[Unregistered]

No we did not.

 

[Unregistered]

We used Primer G product undiluted one coat and Mapei Proflexible adhesive.
We didn't commission the UFH before we tiled, which we now realise was incorrect.
thanks for your offer for advice.

 

[Stef]

J&K that is rather deep for putting addy on the floor to build it up, as Lee says I would use Anhylevel to bring that floor up to reduce the depth of the adhesive.

Unregistered, you must commission the ufh before you fix any tiles to the substrate & as Sean says you must do a moisture reading on these screeds to make sure the RH is 75% or below then it's good to go.