ᐅ Insulating a concrete floor with rigid foam boards and then installing tiles on top?

Hello everyone,

We are currently renovating our home. At the moment, the kitchen has a concrete floor, and below it is an open space. The ceiling of the room below is insulated, but the concrete floor and the tiles always feel cold.

Right now, there are old tiles on the floor. I am considering installing rigid foam boards and then laying new tiles on top of them. This would serve as additional insulation. I was thinking of using boards about 20mm (0.8 inches) thick.

Is this even possible? Could cracks occur? What should be taken into account? Any other ideas?

Thank you very much.

In wall areas, tiles can be applied directly onto rigid foam boards. For floors, this is not advisable because the risk of damage to the tile covering due to cracks is too high. Underneath the tiles, you need a load-distributing panel. This is usually achieved with a floating screed.
If the floor buildup height allows, you could consider a dry screed system: composite elements made of gypsum fiber boards, for example, laminated with insulation.
The thickness of these elements ranges between 28mm and 40mm (1.1 inches and 1.6 inches), depending on the type of element. Example: 18mm (0.7 inches) gypsum fiber board + 10mm (0.4 inches) insulation (wood fiber) = 28mm (1.1 inches).
You can safely tile on top of this dry screed.
There are various manufacturers for these products. You will find considerable information online under “dry screed composite boards” or similar terms.