Is Decoupling With Stone And Ufh Bs? - Tile Advice

[hmtiling]

Hi all, got a couple to price up with pumped floors, ufh and stone. I want to use durabase/ditra and, being aware it's best practice, just wondering if it's also british standard to do so. I've been in touch with Schluter and Dural and got different opinions whether it is or not from them, and awaiting emails from both to show clients. If anyone can definitively tell me yes or no I'd be very grateful. And if anyone can quote the relevant British Standard they'll get a xmas card!
Many thanks in advance.

 

[Ajax123]

Yup. BS5385 says natural stone with heated screed should be uncoupled. It doesn't say how but a mat seems the logical solution. It is also a recommendation of the British stone federation.

 

[hmtiling]

Many Thanks Ajax.

 

[hmtiling]

After asking around, this is all I can find on decoupling in British Standards;
From BS5385-3:2014 clause 5.5
Polyethylene or suitable sheet membrane should be used in preference to
building paper or bituminous felt. A minimum thickness of 0.125 mm should be
used for most conditions, the purpose of the separating layer being to ensure
that the applied screed or concrete does not adhere to the base.

NOTE Uncoupling membrane systems provide an intermediate substrate between
the tile covering and load bearing substrate. They can be used over a variety of
substrates, which include timber, concrete, cementitious screeds and gypsum based
screeds, etc. They are designed to neutralize lateral stresses that occur between the
substrate and tile covering; they are not designed to accommodate differential
vertical movement. The membrane works by preventing stresses from the substrate
being transferred into the tile covering; this prevents cracking and possibly
delamination of the covering material. They are designed to work with tile adhesives
where the bedding does not generally exceed 10 mm.

It doesn't mention heated screeds or even recommend anything. Is there a bit on this subject I've not found?

 

[Spud]

the stone federation recommend uncoupling all stone floors over heated screeds give them a ring and they will help you more

 

[hmtiling]

Thanks Gary. I emailed them and they said I need to be a member for technical advice.
I'll try giving them a ring.
Cheers