In A-2 residential districts, the only uses which may hereafter be established are those permitted in A-1 residential districts and in addition the following:
Single-family residences, excluding trailers, each on a building plot or lot of not less than one hundred feet (100') average width and twenty thousand (20,000) square feet in area, excepting any smaller lot or parcel of land of public record on the adoption date of this title or on the date of the annexation thereof to the village. (1983 Code)