Screed with central heating pipe duct

[White Room]

You could at a push use Dural/kerdi/homelux over the ducting and bring it 6" over onto the screed either side, then there won't be any hight issues and will cover for any movement you might get on the ducting

 

[Jackswan]

Thanks whitebeam, sounds good.
Just reading a posting on this forum
cracking screeds/tiles and underfloor heating
about cracks in screeds and how to repair them before tiles are fitted.
Using PCI PECILASTIC which apparently is only 0.8mm thick, but is it any good? This would be a good solution if it could just be laid say 6 inches either side of the ducting.
Where would I be able to obtain some of this from if it was suitable?

 

[White Room]

Pjc uses pci and rates it highly