Minimum floor area. No one-story dwelling shall hereafter be erected unless the building has a minimum floor area of 1,200 square feet. No two-story dwelling shall hereafter be erected unless the building has a minimum floor area of 800 square feet on the first floor. No building shall be considered a two-story dwelling unless the second floor thereof shall contain at least 75% of the cubic contents of the first floor. For purposes of this section, split level homes shall be considered as a two-story house.