Tiling over electric mat

[alba2]

If there is a chipboard floor and an electric mat for underfloor heating is to be laid, is it necessary to lay ply over the chipboard first or can the electric mat just be screeded onto the ply?

 

[PrenticeBoyofDerry]

If there is chipboard floor, I would always ply over it, if lay tiles.

 

[alba2]

Thanks for your reply. But there is an electric mat for underfloor heating that has to be laid in a fairly thick screed first. Is it still necessary to lay ply first, then the electric mat with the screed?