@DeanXeL , thanks, I kknow that, and I use that a lot. But it´s strange though, cause it says, that the rooms isn´t anymore a room but only something, that looks like one. And this bothers me. And I think, that is, what Xinqun meant with the word "exploded".
A staircase shouldn´t kill a room. And aside from the fact, that I can indeed destroy the friezes that way, it can happen, that there are some, that are really hard to recognize, and then they get in the way, if you want to place something else. And you search and search for the reason, and you can´t find it.
Also it bothers me, if it comes to wallpapers, as they also need to be placed as single ones, after opening a ceiling. I mean, I have to live with those problems but I don´t like them. Why this room tool, if it doesn´t work like it should? It was so much easier to build in the older games of this series, and the few advantages, Sims 4 really makes, are mixed up with bugs everywhere. That is too sad, cause I really like things like that platform tool, that is so useful, or what we can do with roofs nowadays.