Black 2cm thick tar layer instead of screed??

Mastic asphalt is perfect for underfloor heating. We poured it in immediately. However, copper or stainless steel is then required. You can use plastic. Your mentioned structure makes sense. Regarding max. weight, in the worst case you should ask the structural engineer.

Can you tell me more about your floor? How long did it take to dry and how practical is it for everyday use? Do you also have it in the wet room?

Thank you Rick for the detailed answer. A follow-up question We want to install underfloor heating. Is cast asphalt suitable for that? Flooring would then be: Cast asphalt (instead of other impact sound insulation) Separation layer/dimple system Underfloor heating/pipes Screed (maybe somewhat thinner than usual?) Vinyl Does that make sense? I also have some concerns about the weight(!) and the construction. Assuming the cast asphalt would be just as thick as other impact sound insulation.

I don't understand. You have an "expensive" cast asphalt and then vinyl on top...

I have mastic asphalt as the final coating. We only recently built. The TE has an old existing house with mastic asphalt with parquet on top.

@Rumbi441You can see the exact process in my building thread. One layer to "glue" the cables and pipes, then a layer with admixture and scattering. After one day it is cold. Then it has to be ground. Everything that comes into contact with the asphalt must be heat-resistant. It is applied at about 230 degrees. Nothing has to dry because there is (almost) no water contained.

Great for everyday use. Warm to the feet, cushioning, waterproof, etc. Also very low maintenance. It is not used without reason in industrial areas.

But for one room, the effort is too great. We have the floor everywhere. Also in the shower.

https://www.hausbau-forum.de/threads/bauhaus-villa-aus-beton-mit-Kerndämmung-erfahrungen.28733/post-393553

Here begin the posts about the installation at my place.

Screed (maybe a bit thinner than usual?)

You can forget that, the underfloor heating pipes need a minimum coverage of 45mm + 5mm tolerance.
So with 17mm pipes you already need 67mm, better 70mm, which is then not really thinner...
Applies to cement screed, don't know if other screed types allow less coverage.
Ah just checked, calcium sulfate screed may be 5mm thinner. That doesn't really help much...