In any zoning district in which single-family dwellings are a use
by right, notwithstanding the regulations imposed by any other provisions
of this chapter, a single-family detached dwelling which complies
with the yard, space, and bulk requirements of the zoning district
in which it is located may be erected on a nonconforming lot adjacent
to an improved street. Nothing in the requirements of this chapter
relating to lot area per dwelling unit shall be held to prohibit the
erection of a single-dwelling unit upon a lot having less than the
required street frontage or the area of which is less than that prescribed
as the lot area per dwelling unit, provided that such lot, at the
time of the passage of this chapter, was held under separate ownership
from any adjoining lots or provided that, at the time of the passage
of this chapter, a recorded plan of lots or subdivision of property
shows such lot to be a separate and distinct numbered lot.