Problem concrete and chipboard substrates

[Rolandk]

Hi,
I've taken up the existing floor tiles ready to re do the kitchen floor. Good news is they came up really easy complete with adhesive and a few mm of the very dry concrete substrate too! The concrete is very rough and uneven in places and seems to be the original slab with no screed or SLC. I was going to put electric UFH direct on the concrete using a thermal primer first. Now having a re think and might use 6mm Marmox boards to get a better surface for UFH and tiles although this gives me a bit of a floor level problem but might have to live with that. Just worried that the Marmox might not bond Ok to the concrete so what would you advise please? Also part of the floor will now be tiled onto green chipboard (A no no I guess?) so I guess the Marmox over this would be better too? Will the Marmox stick to the green chipboard or can I screw it down?

Thanks in advance,
Roland

[Ajax123]

if you don't insulate you will end up using the whole concrete slab as a heat sink and an electric mat will struggle to deliver enough heat.

[Rolandk]

Thanks Ajax I figured that would be the case and what with the state of the substrate I decided it's the way to go. How about my concerns about getting the marmox to stick to the dry lumpy substrate? And to the chipboard?

Cheers,
Roland