Do not be mistaken, in this case it is not a detailed description of the dwelling of Hobbits, nor other small beings, whose living quarters are somewhat tight and uncomfortable for the European grown-up. Even in a regular house there are rooms where the walls are somewhat lower than usual. This is especially the attic space under the saddle roofs. This, of course, often relates not only to the lower horizontal parts of the ceiling, but, in particular, to slanted parts, which are hard to say, whether it is considered a wall or, conversely, a ceiling. In this case I propose to consider the bevel to 45 ° as the ceiling and above 45 ° behind the wall. But I do not know how to define the bevel exactly 45 °. We leave to the discretion of every reader.
What you do not miss
Whatever the degree of slanted, it is likely that in any case you will need to use the so-called roof windows in order to ensure sufficient natural light in the space.