Hi there, hope someone can offer some advice. We would like to lay electric underfloor heating, tiled over with ceramic floor tiles. But one half of the room is concrete, the other is (floating) wooden floor boards - ie room was originally 2, now opened out. The concrete half is pretty rough and uneven, with some areas of brick from previous dividing wall which is, slightly depressed (2-3mm). Floorboards are all fairly sound.
How do we level these two floors and prep them to lay thermal boards and then electric cable/matting before tiling over, without risk of future cracks/movement etc?? Is there a way of levelling off the whole floor with a single material? We suspect it's not possible to lay self-levelling screed directly onto the floorboards. Hope this is clear!

Hello and welcome..

When you say floating.. is the floor onto joists or just laid onto insulation..?.. are there any fixing in the boards..?

What deflection do you have between the the timber and the concrete side..?

Thanks for the welcome! Floor boards are fixed onto timber joists, with old iron floorboard nails - it's an old victorian house. Not sure what you mean by deflection tho!