All of the items in a group, even if not part of the "hole" must be positive?  For example, I have a window that was placed in a window "hole" that is neutral.  It's a doorway that will not form, which I attempted after the window.  Of course, the window "hole" went fine and I simply slide the window into the hole and made a group of everything, then attempted the door.

EDIT:  I tried that just now, but I still cannot add the doorway.  After making the house - adding rooms- I turned the window I placed in the window opening positive, then grouped it and made the group positive.  I still cannot make a doorway...

The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' (I found it!) but 'That's funny ...'
Isaac Asimov (1920 - 1992)