ᐅ Very low installation height with underfloor heating in an older building

Good evening,

I have the following "problem" regarding the floor construction in an older building. After removing the old mastic asphalt, we found that the total buildup height including the covering was 50/55mm (2–2.2 inches). A new height of up to 70mm (2.75 inches) would still be just acceptable, especially regarding the door frame height and the transition to the stairwell. An underfloor heating system with 15mm (0.6 inches) pipes is planned to be installed.

I have done some research and discussed options. My preferred solution looks like this:

- Studded insulation panel (including 10mm (0.4 inches) insulation and embedding of the heating pipes): 30mm (1.2 inches)
- Thin-layer screed: with at least 20mm (0.8 inches) coverage over the studs
- Glued parquet flooring: 10mm (0.4 inches)
= Total 60mm (2.4 inches)

We plan to implement this on the ground floor above an unheated cellar. We also have the option to insulate the cellar ceiling from below.

I would be very grateful for any assessment or alternative suggestions. Unfortunately, we have very little leeway left, especially regarding insulation.

Best regards and thanks in advance.

Chrizz72 schrieb:

I would be very grateful for an assessment or alternative. Unfortunately, we probably don’t have much flexibility left, especially regarding insulation.

Either the option you mentioned or just a "standard" construction:
- 20mm (3/4 inch) insulation (e.g., PUR, which also holds staples well)
- Membrane with installation grid
- Underfloor heating with 16/2 mm (5/8 inch x 1/8 inch) pipe stapled in place
- Suitable screed (thin-layer screed)

Personally, I would choose the version with studs, since the pipes sit more securely and won’t be pushed upward (60mm (2 3/8 inch) total build-up isn’t much). But it’s essential to insulate the basement ceiling.

Finally, an alternative with cast asphalt screed. This only requires a covering of 15mm (5/8 inch) over the pipes with a total thickness of 30 or 35mm (1 3/16 or 1 3/8 inch) (not sure exactly).

Axolotl2022 schrieb:

Either the method you mentioned or just a "standard" build.
- 20mm (about 0.8 inches) insulation (e.g., PUR, which is also easy to staple onto)
- Membrane with layout grid
- Underfloor heating with 16/2 mm (about 5/16 inch) pipe, stapled
- Suitable screed (thin-layer screed)

Personally, I would choose the dimpled membrane option because it holds the pipes more firmly and prevents them from being pushed up (a total build-up of 60mm (about 2.4 inches) is not much). But it is essential to insulate the basement ceiling.

Finally, there is the alternative with cast asphalt screed. That only needs a covering of 15mm (about 0.6 inches) with a total thickness of 30 or 35mm (about 1.2 or 1.4 inches) (I’m not exactly sure right now).

I am also considering the stapling plate method > with 15mm (about 0.6 inches) thickness, the total is also around 50mm (about 2 inches). Somehow, though, I’m leaning more towards the dimpled membrane option...

I probably can’t avoid insulating the basement ceiling!? Maybe I’ll do it later if I’m sure that the energy consumption is too high.

Thanks for your input, Axolotl.

I think this should work. There are also underfloor heating manufacturers that offer special thin-layer systems. These use relatively flat "heating elements" instead of traditional heating pipes. It looks like this:

This is then covered with a suitable thin-layer (quick-setting) screed. If I remember correctly, they advertise a build-up height of 4 cm (1.6 inches) excluding insulation.

However, I estimate it is more cost-effective to build in a fairly conventional way, just somewhat thinner.

Chrizz72 schrieb:

If necessary, I will do it afterwards, once I’m sure the energy demand is too high.

Insulating the cold basement ceiling is actually, besides the top floor ceiling, the most effective do-it-yourself measure with the highest energy-saving potential. It should ideally be done before installing underfloor heating. You will really feel the warmth at the basement ceiling from the basement side. A three-figure amount of heating costs is lost there.

Axolotl-neu schrieb:

Insulating the cold basement ceiling is actually (along with the top floor ceiling) the most effective DIY measure with the highest energy-saving potential. It should ideally be done before installing underfloor heating. You will really feel the heat at the basement ceiling from the basement side. A three-digit heating cost amount is lost there.

Yes, I totally believe that! Then I’ll do it right away...

If you have any tips on how and with what to do it best, I’d appreciate it... 🙂