UK Electric underfloor heating onto concrete floor.

[Teign Tiler]

I have a customer who lives in a 200 year old property. The lounge floor he wants tiled which is very thick concrete. He wants electric underfloor heating but I'm concerned he'll lose too much heat into the concrete.
He's gone with tumbled modular limestone and the floor is quite wavy which they want to keep but all the insulation I've come across is boards which will flatten the floor out too much, ( he wants to follow the slopes on the floor )
What other options are there please, or will a decoupling membrane with the heat mat on top be sufficient? Cheers Gav.

 

[Tile Marble Granite]

Sometimes you have to go along with the customer and do what he asks for. If you worry too much you might lose the job and he will hire someone else.

Here is a link to Schluter Ditra Electric Heating

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Electric heating | Schlüter-Systems

Warm feet guaranteed. Precise timing and quick heating of surfaces is possible with our Schlüter-DITRA-HEAT-E electric floor and wall heating.

eu.schluter.com

 

[AliGage]

Am I reading this right? Your customer wants an uneven floor??
Would be difficult to tile modular/opus if the floor is all over the place!

However, you can still insulate the substrate using marmox/wedi etc. just glue and screw it. Mechanical fixings will pull the boards down maintaining the undulation your customer wants 🤷🏻‍♂️