The dreaded Anhydrite/freeflow screed - TilersForums.com

[Gazzer]

As an ongoing contract i have been tiling a property with screed that i was told was Freeflow screed. No problems up till now. The screed was dry and any laitance was removed and then 2 coats of primer (90 degrees to each other) were laid. Dural Ci was laid with SPF adhesive then the Travertine laid on top of the dural again using SPF.
The problem is now, the next stage of the job is ready for tiling....or should i say, the owner is wanting it tiled. The floor is still very wet, this is known by the colour and feel. I do have a cheap moisture tester and this said the same.
I have told them of all my concerns and they understand but still they need the job doing. I wont be tiling until i am happy the screed is fully dry, my problem now is finding the appropriate literture that i could print off and show them. Something in plain English would be ideal, do any of you know any links that i may be able to get this from?

Also what is the best way of drying a floor?
I have said that open doors and ventilation is the best, second would be a dehumidifier. They are saying a space heater !, I feel this could make thinks worse by making the room sweat and maybe crack the floor if heat was to high and too close .

 

[top tiler]

dehumidifer i would say is the way forward a space heater makes the room sweat as you have said yourself .we have only done 2 floors on anhydrite screed the first was a showroom in summer preped as you did no brobs the 2nd was a house in winter floor was dry when we tiled it then over the christmas shutdown they left the de hum on it overflowed went under the tiles and the whole floor come up will not tile on this stuff any more not worth the agro that comes with it

 

[grumpygrouter]

Doesn't the durabase work the same way as Ditra Neale, in that you can use it on new screed as long as it is solid. The construction allows the moisture to get out and doesn't lock it in?

 

[top tiler]

grumpy what do you stick the durabase down with?

 

[Gazzer]

Yep just spoke with client and explained i wont take the risk. He is understanding and after talking with Mapei i feel i have made the right decision.
Just have to wait for the floor to dry out before i can start.:mad2:

 

[Gazzer]

Doesn't the durabase work the same way as Ditra Neale, in that you can use it on new screed as long as it is solid. The construction allows the moisture to get out and doesn't lock it in?

Having just got off the phone with Mapei tech they say floor must be dry, if not the screeded floor can "turn to mush" (their words not mine).

My way of thinking was that the water would eventually come out on way or another and could debond the adhesive holding the Dural Ci.

I prefer the safe option and let the floor dry, i like to sleep at night.

 

[grumpygrouter]

grumpy what do you stick the durabase down with?

Thats a good question. I have not had to tile a wet screed yet so have not had to think about it. I believe (though don't quote me) that Schluter say your normal choice of adhesive for the substrate is sufficient.

 

[Gazzer]

I would also like to point out that this area to be tiled was in the open for a few weeks before the roof of the conservatory was put on. Although they did put up a make do roof out of polythene, it collapsed with teh bad winds and heavy rain. This left the floor flooded with over 20mm of water all over.

 

[grumpygrouter]

Can't you treat it like a swimming pool Neale?

 

[top tiler]

thats the problem! you would have to grind the floor put 2 coats of sealer on it then the matting so you have sealed the floor? anhydrite is a diffrent animal to normal screed its just like tiling on to plarster but softer and it soakes up all the moisture in the air like tiling in a big spounge