ᐅ Underfloor Heating vs. Ceiling Height: What Should You Do?

All these plans are driving me crazy 🙁 There was an attic conversion 10 years later, and in this cross-section, the lower value is shown again 🙁 I guess the only option is to measure it myself...

Even if you stick to the current 6cm (2.4 inches), I don’t see any issues. It is usually recommended that the screed coverage over the underfloor heating pipes should be 45mm (1.8 inches), while the pipes themselves are calculated at 20mm (0.8 inches) – typically 16mm/17mm (0.6 inch/0.7 inch) pipes with an insulation board underneath. This results in a “standard height” of 65mm (2.6 inches) for a heated screed.

Depending on the screed composition, however, as far as I know, only 35mm (1.4 inches) of coverage might be possible.

In this case, it is probably not feasible to use stapler plates, as these usually require at least 20mm (0.8 inches) of insulation as a support layer (the staples need something to hold onto). Instead, you could use dimpled membranes without insulation or possibly a Velcro system, and install the necessary insulation layer from underneath on the basement ceiling.

The mechanical ventilation with heat recovery can probably be installed elsewhere as well; it doesn’t have to be integrated into the floor structure (personally, I’m not a fan of that anyway, because it often requires very small cross-sections with unfavorable pipe dimensions, such as oval rather than round).

Another option would, of course, be to build the floor structure higher. The problem areas “stairs,” “doors,” and “windows” have already been mentioned. If I remember correctly, you were planning to completely replace the windows anyway; so that should not be a problem. Possibly, there could be insufficient sill height for non-floor-to-ceiling windows (in Hesse, I believe 80cm (31.5 inches) is required). However, it is generally not difficult to add another row of bricks above the window.

Raising the lintel over the doors is also straightforward and maybe even desired (2.11m (6 ft 11 in) instead of 1.985m (6 ft 6 in)).

As for the staircases, you would need to check – according to DIN standards, you are allowed a deviation of up to 15mm (0.6 inches) on the rise of the first or last step. Alternatively, you could work with so-called “renovation steps” (which might be wanted for aesthetic reasons anyway) and distribute the additional required floor height evenly over the steps.

Dr Hix schrieb:
possibly intended for aesthetic reasons anyway?) and to distribute the additional required build-up height evenly across the steps.

Exactly, that was the idea anyway, since the stair treads are already marred by drill holes for a stairlift.
At the moment, I am preparing for the worst and calculating with a room height of 2.50 m (8 ft 2 in) plus a 6 cm (2.4 inches) screed. I am currently browsing the internet and have also come across dry screed systems that advertise build-up heights of 5 cm (2 inches) or less including the floor covering. Alternatively, there is also the option of milling. The screed would be thick enough for that, but I am unsure how that would affect the insulation, meaning how much would be lost through the floor slabs.

Dr Hix schrieb:
The controlled residential ventilation system could also be installed elsewhere

We are glad to hear that, but what would the alternative be? Suspended ceilings are not possible either, because then you have the height issue again.

Brief note: The current floor structure is 6cm (2.4 inches) thick. What exactly does this mean? How much of that is screed, and how much is parquet, laminate, or similar?

The controlled residential ventilation system can be concealed within walls and the suspended ceiling, under the screed, underfloor heating, and the rest.

In load-bearing walls and walls with only 11.5cm (4.5 inches) thickness like in this house, probably not. This is a matter for the structural engineer, who will likely need to be consulted for any changes to the floor plan anyway.