Does Sloping ceiling only work in top level?

[yminus]

I followed the Tutorial for sloping roofs and ceilings, dormers and more with success to create a sloping ceiling. Then I was surprised to find out that it did not work with my own model.

After long hours of testing and checking my coordinates I found out, that the slopes are applied if I remove the attic (the top level).

How can I have sloping ceilings in the second top level?

[yminus]

Meanwhile I found some related threads.

• BUG: Sloping slope works as soon as new level is created
• Windows in a inclined roof

If the answers to those threads are still valid, my question is answered.

It is a pity that windows have to be positioned before ex-/importing them. I am planning the reconstruction of an attic floor including a rearrangement of the flat roof windows.