Help!: Ceramic tiles on anhydrite screed floor

[posh_merkin]

Hello,

I am Mike and I am in the middle of a self build house project in Aberdeenshire Scotland. I have anhydrite screed down on both the ground floor and the first floor, over wet underfloor heating. There are a total of four rooms (bath/shower/utility/kitchen) that will have ceramic tiled floors. I have read several articles on line telling me I must have a membrane/must sand down the screed/must prime with ANOther primer etc before tiling and am most confused. What would be REALLY USEFUL would be a well written summary of ALL the different methods and their pros and cons. Surely in any case there must be a non-cement based tile adhesive that would work without the need for a whole heap of preparation work?



Thanks in advance

Mike

[Sir Ramic]

There is such an adhesive. Weber Col, Kerakoll make one H40 I think. Creative Impressions GBTA is another.....actually getting some of these adhesives is another story.

[Dontiler]

hello Mike
There is plenty of information on forum about tiling on anhydrite,
but these screed are not recommended in wet areas as you mentioned shower room

[PHG Wetrooms]

There is such an adhesive. Weber Col, Kerakoll make one H40 I think. Creative Impressions GBTA is another.....actually getting some of these adhesives is another story.

just wanted to give a quick heads up on the 'Anhydrite friendly' Kerakoll adhesive. In conjunction with Dave Howe we tried this at the back end of last year in the hope of a safe route of tiling onto Anhydrite screeds. It was used to stick Dural CI membrane but when Dave tried to tile onto the membrane the following day the adhesive was not set, in fact it was still wet!
When we checked with Kerakoll we were told that it should not be used with a membrane on top as that would restrict it from drying out!!!.... ie it is a dispersion adhesive.

[posh_merkin]

Thanks to all who responded, in particular for the warning about Keracoll. I have decided to take the safe route and

1. Remove all laitance
2. Prime with an (easily obtainable) british primer from the likes of BAL
3. Use a british conventional flexible tile adhesive

I spent several hours trying to track down some of these European products that are designed to stick to anhydrite screed and gave up.

By the way, the screed over UFH on Lewis Dovetail sheeting on (suitably beefed up) wooden joists for the upstairs of my house has worked a treat. We cast the floor last friday.

Rgds

Mike

[deanotile]

do not forget the 1 day per 1mm drying time*

[Ajax123]

I fail to see the logic of calling a cement based adhesive with a gypsum based screed the "safe route". This is probably the least robust route. You really should check out GBTA from creative impressions and gypfix from nicobond. These are both gypsum based so will not chemically react with the screed. If you do use cement make sure you follow manufacturers advice properly. Do not cut corners. A membrane is not a requirement necessarily

[impish]

Thanks to all who responded, in particular for the warning about Keracoll. I have decided to take the safe route and

1. Remove all laitance
2. Prime with an (easily obtainable) british primer from the likes of BAL
3. Use a british conventional flexible tile adhesive

I spent several hours trying to track down some of these European products that are designed to stick to anhydrite screed and gave up.

By the way, the screed over UFH on Lewis Dovetail sheeting on (suitably beefed up) wooden joists for the upstairs of my house has worked a treat. We cast the floor last friday.

Rgds

Mike

If you do this I would recommend you speak to BAL's technical helpline and get them to provide you with a number for one of their PSTs (product support technicians).
They would be happy to advise on this route and as long as you follow their instructions (to the letter) you will have the security of their 25yr guarantee.
(It's not so darn expensive for nothing!)

[deanotile]

BAL 25yr guarantee.

[impish]

Why so funny?!

Am I missing something?