Removing screed for underfloor heating

Hello dear forum,

I am currently in the process of obtaining the effort and price for the renovation of an old building (built in 1955). We would like to have underfloor heating in the ground floor and in the bathrooms. Now to my questions:

Should the screed be removed and everything rebuilt? What does that cost approximately per sqm?
Leave the screed and work with a flat variant? But with which one?
Are there other possibilities? Milling technology?
How is it with the installation height? I definitely do not want to change the door lintels.

Thank you very much

Hi Nils

First of all, you need to know the current structure.
Tendentially, I would remove the old floor structure.
With the build-up variant, you would probably lose valuable cm of clearance height at the doors.
With the milling variant, I would be deterred by the effort and the risk that the screed might break.

Olli

I advocate for yes. We did it that way too. The main reason was that in the old building there was no insulation under the floor slab and none above it either, and we didn’t want all the heat to disappear into nothing. Also, we converted to an energy-efficient house and therefore floor insulation was mandatory. With a total of 10.5 cm insulation plus an OSB board in between for stability, it was clear that the screed had to go. That brought about 6 cm. The underfloor heating was a dry construction system (we could and did not want to bring hectoliters of water into the old building) with a construction height of 45 mm, of which 25 mm insulation is already included in the above-mentioned 10.5 cm. The new screed is accordingly 2 cm thick. It can certainly be thinner but at what cost, and then again only wet. Since there is no basement underneath anymore, the thick insulation had to be under the underfloor heating and I would never do without it. If you have a basement underneath and enough money, you can insulate from below and use a honeycomb system; then, without milling, with honeycomb panels and casting compound, you get a total construction height of 1 cm.