Build pieces ignore gravity? 2nd floor built before 1st floor

I was trying to blueprint out and build a multi-story castle and the people started building the 2nd floor in the sky first, completely ignored the first floor, maybe because there was dirt there? There were no walls up, because I wanted stone walls and I guess they hadn't learned yet. So I ended up with a floating 2nd floor. Not that bad of a bug and a bit funny.