Foam plastic in floor under bathroom

[KVC]

We are renovating the bathroom on the ground floor in a split-level house, and the craftsmen have chiseled up to move the floor drain.
What should be done with the foam plastic, does it need to be replaced or not? We will have electric underfloor heating.

 

[Träabetare]

You can recast with eps-cement

 

[KVC]

You can cast again with EPS-cement

Aha! So you don't need to replace the foam insulation then? Doesn't that affect the insulation, considering it's a slab on grade? I don't know how EPS-cement works.

 

[Träabetare]

https://www.epscement.com/

 

[KVC]

But if we choose to install foam plastic, is it just a matter of cutting and filling in where they have chiseled? How do you handle it around the floor drain?