No one-story dwelling house shall hereafter be erected unless the building has a minimum ground floor area of 875 square feet exclusive of porches, basements, breezeways and attached garages. No two-story dwelling house shall hereafter be erected unless the building has a minimum ground floor area of 585 square feet on the first floor exclusive of porches, basements, breezeways, and attached garages. No building shall be considered a two-story dwelling unless the second floor thereof shall contain at least 50% of the square footage floor area of the first floor, using a minimum four-foot knee wall.