I have an underfloor heating element laid on a 6mm thick insulation board. When I walk on it, I can feel that its slightly springy.
I want to pour a self-levelling compound on top as a finish but I did this before in my other room and the concrete ended up springing slightly and resulted in cracks along some places - mainly in the gaps between the heating elements because these also provide some reinforcement as opposed to just the bare foam board. So I stuck a strip off a recycled cardboard roll into the gaps, and it's less springy already.
But I worry that its not enough and wish I could do more.
Maybe some thin plastic stiff sheet which would have small holes in them (as opposed to a plain sheet) so as to not block any of the heat and yet provide some reinforcement for the concrete. But where do I find any suitable plastic tiles like that?
The concrete will be as deep as 1.5cm or more at some places, and vanishingly thin at others because the difference in height is 2.7cm all of which I can't level without creating a step into the room and shortening the doors.
Alternatively, I thought of just putting a carpet straight on top of the heating element. But then I worry that furniture like a chair with thin legs could directly press onto the heating element causing damage.
Laminate flooring would be ideal but that would require too many specialized tools and for my crazy uneven floor it would result in an ugly job like it was before.. so a new more-levelled floor would look better I think.
The reason for the big difference in height is because it must have cracked from some pressure underneath. Some places in the room are just higher up without a crack so I'm not just levelling to cover a crack.
I drilled holes into the subfloor for levelling screws and a bit of air escaped and even now I'm starting to feel a few bubbles forming underneath the insulation board. This is one of my other worries that pressure could also crack the concrete. But maybe I just drill a few tiny holes into the resulting levelled compound to allow air to escape?
Maybe I mix my own cement and sand (results in a very strong cement) and use floor tiles with a levelling ruler, and tile straight on top of the heating elements? But not sure how cosy that is for a living room.
I just want a second opinion.