I've been bugged by the Mauryan house's foundation ever since I noticed that it's way too big. After playing around a bit I also noticed that their farmstead's obstruction's wrong too. So I decided to take a look at every building and see if there were adjustments that could be made.
In general I tried to match the obstruction with the visual edge of the building, and put the foundation 2m beyond that.
Some buildings have steps which can be hard to take into account, or maybe the building isn't quite centered.
Keep D651 in mind for a few of the larger foundations.