Re: The triangular wall box does not have floor and ceiling.

The triangular room object still has floor and ceiling in my game.  If you haven't already, please make sure that you've removed your mods, cleared your cache and repaired the game via Origin.  Also, for testing purposes, it would be best to try again in a new save.

Edit:  Also, as I'm looking at your picture, you have your camera at ground level.  You need to go up a level in order to see the ceiling...