On page 49 it is said, that a gatehouse is 20' x 30' and has 10' thick walls. By these measurements there should be no interior room, right?
Is this a bug or is are the dimensions of the buildings meant to be the room sizes and not the complete diameter of the building?
Hah! I actually had to go look up the answer to this in my Mathematics Behind the Scenes excel spreadsheet.
The gatehouse is 30' wide, 30' long and 20' tall. Its walls are 10' thick. Therefore it has a two story interior with each interior measuring 10' x 10'.
Ah yes, that makes more sense. Thanks for your fast response.
Now that you mention floors: Do floors and stairs come with a building or do they have to be paid extra?
In the core rules, for example, the keep says (80' tall, 60' Square, wooden floors and stairs).
And for the minimum value to secure a hex only fortifications count, right?