Ground floor approx. 100 sqm, upper floor expandable (planned bathroom, 2 children's rooms, 1 storage room)

Yeah, sure, but we already need to know the exterior walls of the rooms now, as these might possibly be erected already. The interior walls are indeed to be erected later, but you can plan that a bit now already.

Yeah, sure, but we already need to know the exterior walls of the rooms now, as these might already be put up at this stage. The interior walls are indeed to be erected later, but you can still plan that a bit now

You are planning something ... thoughtlessly

That is why I am here

That's why I'm here

Sorry, it refers to the fact that you are already mentally moving within the house...

Is the bathroom on the upper floor really necessary and absolutely required?

Regarding the knee wall, I made incorrect statements out of ignorance. I believe here you can see that there is indeed a mini knee wall

You made the incorrect statements about the position of the windows, and I wouldn’t call the naive calculation ignorance.

I will now slowly show you what can be seen in your picture. Namely, that an "k" is missing – you have no knee wall!



I highlighted the exterior wall in blue, mentally extended upward to the top edge of the ceiling beam. The position of the non-existent foot purlin here is marked in red. Its lower edge lies "0" above the blue area, so knee wall 0.

The difference between the length of the green line and 0 is merely due to the "scissors" caused by the roof pitch. That is not a knee wall; that is simply a steepness plumb line.

If you subtract a floor build-up from the starting point of the green line, it will roughly still be about 12 cm long – which by no means makes it reasonable to proclaim a 1m line 88 cm further along.

The construction of the eaves itself is economically solved; considering the current cornice box trend, this is cleverly solved for a laundry string attic (that’s the polite expression for "the bastard who would have planned this as a living space reserve should publicly return their diploma").

If the conversion is not to become an illegal building, the planner who has to get this thermally approved will really be sweating. Starting with the nonexistent exterior wall in the attic, it will be no easy feat to make this upper addition tight to the thermal envelope.

Your idea to count a slat doubling on the rafters, which is necessary solely due to the insulation sheet thickness, as also completing the counter battens is nonsense from the same category as the ten-centimeter floor.

I find this concept of the couple apartment with "build now, think later" attic irresponsible; a professional should have dissuaded you from it by all means.