In any district, notwithstanding limitations imposed by other provisions of this Title, a principal structure and accessory structure may be erected on any single parcel of record at the effective date of adoption of this Title. This provision shall apply even though such parcel fails to meet the requirements for area, width or depth that are generally applicable in the district, provided that yard dimensions and other requirements not involving area, width or depth of the parcel shall conform to the regulations for the district in which such parcel is located, except as provided in Section 17.120.090, variance of yard requirements shall be obtained only through actions of the Zoning Board of Appeals. Such parcels must have been in separate ownership and not of continuous frontage with other lots or parcels in the same ownership at the time of adoption of this Title. If two or more lots or tracts or combinations of lots or tracts or portions of lots or tracts with continuous frontage in single ownership are of record at the time of passage or amendment of this Title, and if all or part of such lots or tracts do not meet the requirements for parcel width, depth and area as established by This Title, the lands involved shall be considered to be an undivided parcel. No portion of the parcel shall be used or sold which does not meet the area requirements established by This Title nor shall any division of the parcel be made which creates or leaves remaining any parcel with less than seventy-five (75) percent of the required width or depth. Except if such a parcel shall be created by the actions of a local, State or Federal agency, then the parcel shall be registered as a nonconforming parcel and considered to be a parcel of record prior to the time of adoption of this Title.