Laying large York stone slabs on an anhydride screed with underfloor heating
Anonymous user 09/03/2024 - 3.04 PM
Anyone any experience laying large York stone slabs over a gypsum based screed with underfloor heating? Seem to be getting conflicting advice as to the decoupling membrane to be used. Slabs are to be laid on a sand/cement bed which needs to be isolated from the screed. Most uncoupling membranes require to be stuck down on a sanded and primed screed. Surely this is not necessary as the weight of the slabs will hold everything in place. The floating membranes stipulate a maximum bedding material of 5 to 10 mm over it. This is insufficient bedding for the thickness of the slabs. Wondered about simply bedding them over a polythene dpm ? Has anyone done this?
Are you a tradesperson and able to answer this question?
Anhydrite screeds are really difficult in terms of tiling. They need abrading before tiling priming before any tiles or substrate. I’d definitely say your right for wanting to fit a tile membrane durabase or any other brand but in terms of the York stone the quality of stone will be a deciding factor in terms of how smooth it is. As long as the stone has 80-100 per cent coverage in suitable adhesive it will be fine. Perhaps a porcelain tile would be better for heat transfer but I suppose it depends on the look your after. If you get the prep work correct for going onto the anhydrite you can’t go wrong. I’d get the heating commissioned before you tile when the anhydrite has cured and run so gradual heat before tiling so the floor can contract and expand. Do your research for the best adhesives and primers for anhydrite and you’ll be fine.
Answered15 October 2019
18
Anonymous user
With anhydrite screed the laitence needs to be machanically scrabbled from the surface. If you fail to do this the adhesive will not bond and in short time the floor will fail. Once proper preparation has been taken care of you can then file directly onto screed with the proper tile adhesive.
After the drying period is correct hire a floor grinder with pads how to take off a few mil of the surface then the correct primer with the right ratio in several coats using the correct adhesive preferably as to S2 type everything should be fine
the most important thing is the heating system must be turned on after the floor has dried out run at a low temperature for 2 weeks then check the floor to make sure it reads 75% humidity or 0.5 % moisture then Latic can be removed using mechanical machine with 30-40 grit at a low speed hoover the floor then seal the floor 2 coats making sure it is sealed only then can fit the decoupling membrane and tiles can then be fitted
There is another option Bal have bought out a new product the interlocking decoupling mat that is laid direct to the surface so no latic has to be removed as it is not adhered to the substrate it will save on removal and sealing of the floor and it can be installed at 1-1.50 % but the floor still needs to be commissioned before the Bal dry decoupling membrane is in stalled
Please note the heating must be turned off for 48 hours and then commissions a month after the last tile or stone installed and the commission is done again hope this helps
