Is there a professional definition for a story of a house?  I am assuming it has to do with usable floor space relative to footprint, or something like that.  Do building departments have a guideline they use to determine this – is it in a building code?    Per our county building department, our house is 1-1/2 stories with a cellar.  We are trying to add onto our house and have been told that our addition is 3 stories even though it only extends about 2 feet beyond the existing roofline, and is still below the allowable building height.  Any help would be greatly appreciated!