I can see some areas that are colored as Interior that I believe 'SHOULD' be exterior.

As to how to read the 'maps', using the right map, the Dashed Lines represent Arches, Flying butresses, etc.

The Crossed Dashed lines (like a big X) represent Ribbed Vaults:

http://images.google.ca/images?hl=en...gbv=2&aq=f&oq=

If you can find the book, a great little book for mapping is:

Complete Architecture Handbook