How do I copy a room?

Well, I mean on the same lot without saving it to the gallery first. Just grabbing a room and duplicating it in build mode. I thought it would be as easy as moving a room … shift/alt/ctrl click while moving doesnt seem to do a thing though (in graphic programs it's usually pressing alt while moving something). I could swear I saw them doing this in one of the build mode demos/let's plays. (I could be wrong though)

I am basically looking for an easy way to add rooms in the same style without having to paint the walls, tile the floor etc every time.