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.
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[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.