Raise the living room floor level

Insulation on the terrace and inside below the ceiling (e.g. PUR or resol with aluminum coating).

Yes, we had also talked about insulating below the ceiling, but then the rooms in the basement would have different heights, since not all rooms are under the terrace.

I insulate my 60s old building, for example, only with 12cm resol on the outside, to easily meet KfW 55 requirements.

And nothing inside? Yes, that would of course be the easiest solution to just take thinner insulation. But you would usually first discuss that with the energy consultant, right?

I was just thinking whether you can "bridge" the height more cheaply with wooden slats, for example, and OSB boards or something. Or are there then problems with the underfloor heating?

What does stealing mean? I’ve attached a section.

Unfortunately, you only showed the section. But the ground floor (EG) was probably not really stolen or hexed away, but only confused by you on the linguistic level by writing confusion here through a "basement" (Untergeschoss). The sectional drawing rather simply shows a ground floor and an upper floor, no third level.

Because of the insulation of the basement ceiling by the terrace, it is higher than the living area on the ground floor. And this height difference is supposed to be balanced out by screed..

That is maximum nonsense, unsurpassably misdesigned, one might think, but:

Reminds me a bit of the "robber building". But you didn’t notice it on the plan, only once the shell was up.

No, here it gets even worse (if you actually implement the monster of the half-meter-thick!!! floor structure in the upper floor) – because then in the end we would be talking about sixty-one centimeters passage dimension of the terrace doors! – I linked the robber building example for good reason).

Yes, we also once mentioned insulating below the ceiling, but then the rooms in the basement would have different heights,

Yes, do that: split the insulation, do it half above and half below the ceiling, both with compressed thickness materials. After all, you also have to solve the water ingress problem at the terrace door threshold constructively, which also costs height. At the linked location you might have to flip back a bit, overall this detail aspect alone spanned seven pages back then, if I remember correctly. Visually, don’t worry about it, you can bevel it so that it discreetly hides and gives an interesting ceiling underside. With some luck, afterward all your acquaintances will ask you who built you this fancy design mistake. That could easily become fashionable :) By the way, it is not possible to balance that out with screed, only with – constructively here mega-overkill – doubletripletriple doubling of the insulation underneath. What does your general contractor do for a living – butcher? *SCNR*

Yes, we also discussed insulating below the ceiling once, but then the rooms in the basement would have different heights, since not all rooms are under the terrace.

And? Happens in so many houses where the ceiling is dropped in some rooms for spots, etc. We are only talking about small thicknesses anyway.

But you usually first discuss that with the energy consultant, right?

Yep + house planner.

As nordanney writes, PUR sloped insulation, e.g. from 160 mm to 100 mm, should easily meet KfW55 standards (this is also planned with us). But it also depends on what kind of structure (covering) you want on your terrace. If, for example, it is WPC decking or similar, then overall it could look approximately like this:

- WPC + aluminum substructure: 80 mm
- Protective mat: 16 mm
- EPDM: 6 mm
- PUR insulation: 160->100 mm
- Vapor barrier: 1.5 mm

That gives you about 263 mm total build-up, and you still have about 40 mm of leeway (if I read the plans correctly, you actually have 30 cm overall from the top of the concrete slab to the upper edge of the finished floor inside, right?).

Provided corresponding measures are taken (gutter etc.), you can also go for a zero-threshold (terrace door), as long as your general contractor agrees.

If it’s going to be really tight, the vacuum panel option also exists to get a bit thinner – but they are significantly more expensive and depending on total area can quickly become unaffordable.

Hello everyone,
first of all, thank you very, very much for the many helpful answers.

Maybe first of all. The house is built into the slope and therefore has a basement with an adjacent garage and a ground floor (with the terrace).

I just took a closer look at all my documents again (section, calculations from the energy consultant, and offer from the general contractor) and I think I forgot something important. The ground floor with the terrace is partially above the garage and therefore must also be insulated. (Unfortunately, the terrace could not be above the garage because the garage has to be located in the east due to the gentler slope of the property, but the terrace should be in the west.)

In the documents from the energy consultant, I now come to 55cm total floor construction for the living area, with the reinforced concrete ceiling considered as 25cm and only 47cm with 20cm reinforced concrete ceiling for the terrace. The general contractor’s offer states a thickness of approximately 20cm for the reinforced concrete ceiling.

Now I am a bit confused about the different thicknesses of the concrete ceiling. And aren’t 8cm difference in height way too much? Or is it only 3cm difference in height and the house will be 5cm lower? Is that feasible without plaster? I definitely need to clarify that.
But nevertheless, the floor construction of the terrace determines the height of the floor construction inside the house, right? So without the terrace, a lower floor construction on the ground floor would theoretically be possible, right?

I hope I was able to express myself somewhat clearly. Thanks again

I hope I was able to express myself somewhat clearly.

So-so - like many other questioners, you lack the awareness that nobody here can read anyone's mind, and consequently we are always clueless regarding background knowledge until someone enlightens us with some pictures about the context.