Decoupling membrane or not?

[simon87]

I have a 5 x 5m new extension floor to tile. The floor is sand and cement screed laid 4 weeks ago with under floor heating. The UFH has been commissioned and is on, slowly increasing the heat to warm the screed.
My question is whether I will need to fix a decoupling membrane (eg Ditra mat) to the floor before I tile or am I safe to tile directly on to the screed. I appreciate it may be difficult to express an opinion without seeing the job but any advice would be much appreciated.

[kilty55]

hello,personally yes i would use a mat/membrane

[waterfd]

Definately a membrane. You should also follow the guidlines about tiling on a screed with UFH. I was told allow screed to dry then turn heating on to relieve any stresses, this is with water UFH, turn the heat off and allow to cool. After tiling wait 28 days to allow adhesive to cure. Turn heating on to 5-10 deg alllow to settle for 3 or 4 days then increase temperature 1 degree per day until working temperature is reached. I presume this is the same for electric UFH.

[Bri]

What type of tile will you be fitting, ceramic/ porcelain/ stone?


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[timeless john]

I'd ask how deep is the screed for drying purposes and then what tile material you are fixing?

[Stewart]

all good questions above.... as for the decoupler, I would install one!

[Rich]

It is usually a good idea to install a decoupling membrane if cost will allow