A lot which does not contain sufficient area to conform to the dimensional requirements of the ordinance but which is at least 50 feet wide and 5,000 square feet in area, may be used as a single-family building site provided that the use is permitted in the zoning district and providing the lot is on record in the county Register of Deeds office prior to the effective date or amendment of this ordinance. If two or more substandard lots with continuous frontage have the same ownership as of the effective date of this ordinance, the lots involved shall be considered to be an individual parcel for the purposes of this ordinance.