Weigj:

Yes, there is a (rather) simple way to draw a ceiling with a hole in it.

Imagine a square of 4x4 points, top row = 1 to 4, bottom row = 13 to 16.
Now draw a line as follows: 1, 4, 16, 13, 1, 6, 10, 11, 7, 6, 1

Practice a bit on paper, so that you are sure how to do it. Then do it in your model. Activate Create rooms and start drawing your room and opening for the staircase as described above.

Hans