Thin inner wall without holes in the floor?

[Svae]

For someone who has never installed a door frame before, I assume you buy the door frame according to the wall thickness and the door leaves fit in both models?

 

[Mattias_Jo1]

For someone who has never installed a door frame before, I assume that you buy the door frame according to the wall thickness and the door leaves fit in both models?

Exactly.

 

[Svae]

Feedback with results:

I ended up securing the studs in the ceiling/wall with coarse screws and then anchored the horizontal studs with "tension" via the vertical studs.

It has now been about 1.5 years and it has worked very well. Presumably, the weight from layers of OSB + plasterboard on one side and thicker rough sheathing on the other side has helped keep the wall in place.

The door frame was one I found in my brother-in-law's outbuilding, it fit perfectly with the wall thickness!