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Olz
From what she said Deri is sounds like is concrete, then screed, then piped UFH in foam/insualtion, then chipboard.
Crazygirl, the kernean suggestion is a good idea, you'll get a high quality finish without the high risk of failure, you shouldnt consider tiling this floor in any way, it just wont work, you'll end up with a messy looking floor with cracks that will need ripping up within the year and replacing with a suitable floor covering, seriouslly if you tile it your just wasting your money. I know you dont want to hear it but tiling it is the worst possible idea.
Crazygirl, the kernean suggestion is a good idea, you'll get a high quality finish without the high risk of failure, you shouldnt consider tiling this floor in any way, it just wont work, you'll end up with a messy looking floor with cracks that will need ripping up within the year and replacing with a suitable floor covering, seriouslly if you tile it your just wasting your money. I know you dont want to hear it but tiling it is the worst possible idea.