Anhydrite Screed Tiling - TilersForums.com

[J-a-m-e-s_7]

Hi, I have got my kitchen extension floor to tile (6x3m). The floor is anhydrite screed which i had done about 6 weeks ago approx 40mm depth. This will be the first time i will have tiled on a gypsum based screed and after a bit of reading have come across all the possible problems (Mostly down to either bad prep, moisture content or lack of knowledge about the substrate).

I have removed the laitance using an orbital floor sander/prep machine
The tiles i am using are Grespania 600x600 Porcelain Dock

My plan is as follows:
To prime with tilemaster primer either prime+ or grip
Anhyfix to fit ditra
Then use a standard cement based adhesive from then on. Either Mapei or Weber most likely

I am wondering if this is the best route or can anyone suggest a better method as to how they would tackle it. I'm not a tiler by trade (Builder/plasterer)

Any advice would be appreciated

 

[Flintstone]

Does it have heating in the screed?

 

[J-a-m-e-s_7]

No, theres no underfloor heating.

 

[Flintstone]

Imo, I would buy a hygrometer and make sure the moisture content is low enough throughout. Once you have determined that, prime with prime plus and tile with anhyfix. No need to ditra

 

[J-a-m-e-s_7]

Thanks Localtiler! Is there any particular hydrometer you would recommend and what reading am i looking for? i have seen varied readings recommended by different manufactures.

My only reason for Ditra was that from what i understand the gypsum based screeds don't do well with moisture and if for example the kitchen were to flood a little then it would help prevent it reaching the screed and potentially causing further problems. If you don't think it is necessary though. I've always been a belt and braces type of guy lol

 

[One Day]

Skip the priming. There is no need with Anhyfix. Just make sure the floor isn't dusty and use a wet-ish mix.

 

[J-a-m-e-s_7]

Thanks for the advice. Every days a school day haha. I've been working on a number of jobs recently where gypsum based liquid screeds have been used and not one of the builders knew much if anything about how to prep it or even that is was gypsum not cement based. It is all fairly knew to me too so i thought i'd do a bit of research. At least now i know the basics and have been able to point out the possible problems etc when i came across it. Also, about using gypsum based adhesive although it doesn't seem as readily available as the standard stuff.

 

[Flintstone]

Skip the priming. There is no need with Anhyfix. Just make sure the floor isn't dusty and use a wet-ish mix.

Prime 3 to 1 when using anhyfix.

 

[hmtiling]

I'd prime too.

 

[Flintstone]

If you want to use ditra as a water proofer you can but you will need to tape all the joints and seal them, it will cost a lot. I think if you get a flood to that extent you'll be claiming off your insurance anyway !