It really depends on what you are trying to depict. Any map is just a diagram, so intent is everything.

Since this is a map of a structure, I'd assume there is a roof, which mans you are depicting the room floors, battle-map style. You focus should really be on the edges of the wall outlines, not the interior of the wall, unless this is either important to you or important for the purpose of the map. Referencing atpollard's image, there is no "top" of the wall to depict in your map.

You say this is a posh and sophisticated structure, so the interior wall surfaces would probably be parged/plastered over and smooth, not rough as you have them, with the outer wall surfaces most likely a cut stone, or brick.

Do you need/want to depict the detail structure of he wall itself:

| plaster | rough stone | rubble fill | cut stone |

or is it more important to generally indicate the walls overall structure (stone)?

-Rob A>