Screed with "liquid" insulation layer, bathtub on screed?

Hello everyone,

we are building a semi-detached house through a developer and are currently working on the interior construction. During yesterday's inspection, I walked away with two big question marks regarding screed, maybe someone is familiar with this:

1) A floating heated screed is supposed to be installed, and so far I know the screed construction as:
- Raw floor
- Insulation layer as a board, e.g. Styrodur boards
- Tack layer, etc.

According to the company that is supposed to carry out the interior construction, instead of the insulation boards some kind of liquid insulation layer is supposed to be poured in (he couldn’t remember the name), which is supposed to be better than these boards because it spreads more evenly. But with googling "screed construction" I couldn’t find any comparable construction so far. Can someone say something about this, especially regarding impact sound insulation?

2) Since in the bathroom at the spot where the bathtub is supposed to stand there are relatively many cables and pipes coming out, there is little space, and the bathtub frame is therefore supposed to stand not on the raw floor but on the screed, which would not be a problem in terms of weight. Is that common? Strangely, they placed the air heat pump boiler and the solar module system on Styrodur boards, supposedly also for sound reasons, but somehow I already find that a bit odd.

Best regards hyaden

Hello "hyaden". The topic you are addressing here is a special one. Liquid insulation layers, as you write, are suitable for the subsequent rafter insulation in the roof area or for double-planked lightweight wall systems. Openings are drilled into the component and then a (admittedly effective) mass (I will not go into this further here) is pumped into the gaps. However, as a pressure-resistant base, these systems - regardless of the respective manufacturer - are not suitable. Therefore, not for use under screeds! So please do not allow this procedure!! The intended construction is non-compliant because it does not correspond to the generally accepted rules of the trade! -------------- The (please excuse) incompetence in planning and attempted execution is now evident in part 2. A bathtub is always placed on the raw ceiling so that the load transfer can take place via a static component. Floating screeds are not a static component! Rather, screeds on insulation layers in residential buildings (here I refer to the minimum thickness of 45mm) are suitable for loads of up to approx. 250 kg. However, in edge areas where the bathtub is now to be placed, completely different stress conditions act within the screed layer under load. This means that the screed is very likely to break sooner rather than later (as long as you use the bathtub). This planned procedure is also not acceptable and should under no circumstances be carried out!! ------------------------------------ Regards: KlaRa (Sachverständigenbüro für Schäden an Fußböden)

Hello forum,

regarding the bathtub installation, I completely agree with my predecessor.

Concerning the "liquid insulation," I assume it is a bound loose fill, e.g., Thermodur or Airmix 500. Here, insulation beads are mixed with sand, cement, and water to form a thermal insulation screed, installed as a homogeneous component, and after curing, they form the thermal insulation layer.

This procedure corresponds to the state of the art and is intended to prevent thermal bridges. Loose fills are no longer permitted in this area.

After installation, the surface is very sensitive and must be protected until the screed is installed.

Despite the pressure distribution cone under loads on the screed, a statically permanent construction is still created, which is also used in highly loaded areas.

When installing the screed, the manufacturer's specifications regarding build-up height and mortar quality must be observed, as otherwise damage to the screed may occur.

Best regards

Kristof

Hello everyone,

thank you again for the hint regarding the bathtub installation. After the corresponding intervention, the area of the bathtub was cut out and the bathtub now stands on the raw subfloor.

Regards
hyaden