Very low construction height with underfloor heating in old buildings

Good evening,

I have the following "problem" regarding the floor structure in an old building. After removing the old mastic asphalt, we found that the build-up height including the covering was 50/55mm. A new height of up to max 70mm would still be justifiable (especially regarding the height of the door frame and the transition to the stairwell). A floor heating system with 15mm is to be installed.

I have now done some reading and exchanged ideas. My preferred solution looks like this:

- Studded panel (including 10mm insulation and embedding of the heating pipes): 30mm
- Thin-layer screed: with at least 20mm stud coverage
- Parquet (glued): 10mm
= Total 60mm
We would do this on the ground floor above an unheated basement. We still have the option to additionally insulate the basement ceiling from below.

I would be very grateful for an assessment/alternative. Unfortunately, we probably don't have much leeway left, especially regarding the insulation.

Regards and thanks in advance.

I am very grateful for an assessment/alternative. Unfortunately, we probably don’t have much leeway left, especially regarding the insulation.

Either the option you mention, or simply a "normal" construction. - 20mm insulation (e.g. PUR, you can also easily staple onto it) - Foil with laying grid - Underfloor heating with 16/2 pipe stapled - Suitable screed (thin-layer screed) Although I would personally choose the stud version, since that holds the pipes more firmly and prevents them from pushing upwards (60mm total construction is not much). But definitely insulate the basement ceiling. Finally, the alternative with cast asphalt screed. That only requires a coverage of 15mm with a total thickness of 30 or 35mm (I’m not exactly sure) as well.

Either the variant you mention, or simply a "normal" setup. - 20mm insulation (e.g. PUR, which you can also tack onto well) - Foil with laying grid - Tacking underfloor heating with 16/2 pipe - Suitable screed (thin-layer screed)

Although I would personally choose the stud variant, because the pipes sit more firmly in it and don’t push upwards (60mm total construction height is not much). But definitely insulate the basement ceiling.

Finally, the alternative with cast asphalt screed. 15mm coverage is sufficient here with a total thickness of 30 or 35mm (I don't know exactly right now).

I also still have the variant with the tacker plate in mind > with 15mm thickness, I also come to a total of 50mm. Somehow, I tend more towards the stud variant...

I probably can’t avoid insulating the basement ceiling!? Possibly I’ll do it afterwards when I’m sure the energy expenditure is too high.

Thanks for your assessment, Axolotl.

I think that should work. There are also underfloor heating manufacturers who offer special thin-layer systems. They use relatively flat "heating registers" instead of the installation pipes. It looks like this:


Then a suitable thin-layer (fast) screed is applied. If I remember correctly, they advertise a construction height of 4 cm excluding insulation.

However, I estimate that it will be cheaper if you build more or less conventionally, just somewhat thinner.

I might do it afterwards if I am sure that the energy expenditure is too high.

Insulating the cold basement ceiling is actually (besides the top floor ceiling) THE DIY highlight with the highest energy saving potential. It should actually be done before the underfloor heating. You will really feel the warmth at the basement ceiling from the basement. A three-digit heating cost amount is lost there.

Insulating the cold basement ceiling is actually (besides the top floor ceiling) THE DIY highlight with the highest energy-saving potential. This should actually be done before installing underfloor heating. You will really feel the warmth at the basement ceiling from the basement. A triple-digit heating cost amount is lost there.

Yes, I believe that immediately! So I'll do it right away...

If you have a tip on how and with what I should best do it, gladly... :)