You need to take one tiny moment to wiki Stave Churches. The team did a lovely job on the tarred roofs. This is a Viking game... There is another thread that has a vid of a famous Swedish circular defense for those that don't understand the history of walls and moats.
Thatch makes sense, tho indeed not as pretty as it might be - but two kinds of shingles wouldn't have made as good a choice, like not much choice at all. Maybe there is a mod for that, or make one.