W
White Room
What backer boards, hardie don't do 10mm....
floor was down nearly 3 weeks before it was turned on.
I have checked the customers stat (intelligent), as far as i can tell it hasnt been above 27c.
That looks like it's been cooked. Underfloor heating too soon or too hot. What you are describing is classic thermal shock. I suspect some one is not telling you the truth about the sequence of heating post tiling...