@Localtiler After a bit more archaeology, the dark blue is the plastic cover of the underfloor heating element. In this photo, you can see that some of the cracks follow the loops of the element. And yes, there is a crack under the board too. Good spot.Without pulling it up, I can't see if it's extensive or not. What's your diagnosis?
@hmtiling yes, most of the grouting is now cracked. Is it usual to set the ufh within the adhesive like this?
View attachment 101555
