I've solved my problem.
Thanks a lot guys!!

I've already read about the possibility to use a box, but my walls are oblique (i've no 90 degrees angle) and i don't think it is possible to incline box sides. Isn't it?

Yes Hansmex.
I've tried with this option, but what i need to do is create a "partial" ceiling. I have a loft and I've already created the ground wall an so on, but i need to create a ceiling (which is the ground of first floor)only in a limited part of the house.
Can you help me?

Hi all,

i'm trying to draw a ceiling with SW3d, but until now i was not able to do it.
Can anyone help me please?

Axel