I am having a problem with this at the moment, this floor is in screed water heating. I layed a decoupling membrane over a month ago, having been told the heating had been commissioned. I later learned the floor had only been pressure tested, when they did fire up the floor weeks later. Instead of bringing the temp up gradually ( because there is no thermostat, it seems) the heat just went from 0 to full whack.
My problem now is, isolated areas of the floor are showing, what look like shrinkage cracks in the slc over the membrane. These are very small areas, but in two places it seems like the membrane has de-bonded with the sub-floor.
I have had the rep from Mapei down, and he thinks it could be thermal shock. He suggested I remove any loose areas of mat and replace. My gripe is why do the manufacturers of these heating systems not address the issue of having to commission the floor gradually, by not having a thermostat.:mad2: