As I replied in Discord, you draw your house/room as normal, with an exterior wall already selected, you then select the wall tool and draw over the existing exterior walls you want to change with the new exterior wall you selected. You don't draw empty rooms or anything like that.
Thanks to the great Cardenaglo I was able to create more palettes in the rules.txt to create vegetation and tiles from my photoshop file. That led me to improve greatly the fields which was necessary at the very least for orientation as the landscape was getting very monotonous. Now they look good from above and from up close. Some of the cells wil lbe used for houses with gardens (which are scattered all around the map).
I think I'm halfway in the job of recreating 50/60% of the actual crops on the map. That will be enough to create a sense of diversity and interest.
i have added a crop version of the data map that I use to define which crops is which, but also cemeteris, agricultural industies, social housing, etc.
I have also been experimenting with the rules.txt to get objects that are not vegetation but could be used as is to populate the map: graveyards, cityscape, new biomes, etc
i was unsure if I could use the rock tiles to do the shoreline but it's turning out ok now I can do through photoshop. you will notice also the moor biome around beahces too.
I have pretty much finished the first two main islands (I still need to fix a bug while spawning charcter and object though)
And even if it takes ages, the city of Cherbourg is turning from a mess to a clean organized city, i will keep that for another day.
As soon as I fix the bug, I will upload the map with character spawns only on the islands to start with, and if it's ok I will expand.