Raising knee walls: feasibility, costs, alternatives?

Honestly, I am now completely at a loss as to what I mean

I looked up pictures of Zwerchhaus on Google Images, and yes, I do think that’s what we mean... but I don’t quite see the difference from a Gaube.

What we want, maybe it’s clearer for professionals, which we can only express in layman’s terms: We want the slope to start higher so that the space at the wall before the slope begins can be used better. Here, it comes so low that you can’t use those 40 cm at all. You can’t put a bed or a shelf there... a knee wall of 1 m would be ideal OR a “Gaube” within which you can stand normally.

I have described the constructive connections. A dormer is a building component "privileged" under building regulations that must develop from the roof surface - usually at least 50cm behind the outer edge of the exterior wall - and explicitly must not stand on the exterior wall. Otherwise, it would be a so-called "Zwerchgiebel" or called differently regionally, which triggers completely different setback requirements under building law and for this reason often cannot be realized.

If you want such detailed questions answered in a manner that is approvable and correct under building law, it is best to contact the citizen service of the responsible building authority or consult an architect.

Information from the internet is rarely accurate without knowledge of the local conditions, including misunderstandings about terminology.

Let's assume that what is rising from your attic floor is not an internally built knee wall, but the ascending exterior wall. Then with a dormer, you have to set back by half a meter (or if you get approval for a cross gable, you are allowed to build the wall higher there).

You probably won't want to raise the entire roof; the effort would be too costly, if it is even feasible (and permitted). So let's further assume that you only want to place a bed along there, and above it just make the roof slope so much flatter that it becomes higher at the lower end. Then (in the example of the bed, which should be a little over 2 meters long there) you will have to support and "replace" the roof over the length of three rafter axes.

If the carpenter and the roofer have told you what that will cost, you won’t want to ask the architect anything else, but decide: that will be our junk room.

How is the room supposed to be used anyway?
Although a skylight provides more light, the beautiful view doesn't matter because you only ever see sky blue.

I also don't understand the repeatedly stated opinion that attaching or installing shelves and cabinets is not an option. Then the room hardly needs any other storage furniture. Before cluttering the floor space in question with small furniture, it’s better to install at least that.
After all, every other alternative costs many times more than a few doors, piano hinges, and boards.

Brief regards

One can certainly say that having is better than needing. But one can also ask, do I need the room, for what purpose? If it's just a storage room, leave it. Otherwise, a built-in cupboard and above it a window from Velux. Everything else can wait. One should also let things develop on their own. Karsten