We are currently renovating our 12 m² (129.17 ft²) kitchen and turned on the UFH for the first time yesterday, 3 months after putting the floor in. It was all going well until this morning when I have now noticed that cracks have formed overnight.The floor has dpm, followed by 100mm insulation on top of which are the wet UFH pipes and 75mm of screed (4:1 sand/cement. On top of that is Mapei Ultraplan 3240 SLC.I think the problem is my thermostat is connected to the boiler via OpenTherm, which has inevitably allowed it to ramp the temperature of the flow way beyond what it should have been, despite me manually setting the temperature on the boiler and the mixing valve on the UFH manifold to 30°C (86°F). This has resulted in the cracking.So that's the background, my question is, what can I do about this now? The plan is to tile with 2cm thick terracotta tiles. Do I need to employ some sort of decoupling product? Do I need to somehow reinforce the screed? via /r/DIY http://bit.ly/2KBn48W
