I've been looking into mods which add houses, expand towns etc. and I'm simply puzzled by how the navmesh is modified for these mods.

I'm trying to make a similiar mod myself and need to add buildings in some parts of Skyrim, the Tamriel exterior cell. But when I check the navmesh around the place, it's pretty much everywhere on the land.

Because of this, putting my custom buildings anywhere would just overlap the navmesh laid out, which would probably cause problems with NPCs walking blindly into the buildings.

I've been hearing alot on modders saying how vanilla navmesh should never be deleted or modified.

So if this is the case, how am I supposed to get around this?