All homes with 2,500 square feet or less of "floor area" (as defined in Subsection
19-7.1 of the Borough Code) excluding, however, in determining whether the "floor area" is 2,500 square foot or less, decks, external stairs, unheated porches, detached garages, garages in any uninhabitable area under the first story, all other floor area in any uninhabitable area under the first story, and uninhabitable areas in any attic.