Nothing herein contained shall require any change
in plans, construction or designated use of a building for which a
building permit has been heretofore issued and the construction of
which shall have been diligently prosecuted within three months of
the date of such permit, and the ground-story framework of which,
including the second tier of beams, shall have been completed within
six months of the date of the permit, and which entire building shall
be completed according to such plans as filed within one year from
the date of the adoption of this chapter.
Whenever the boundaries of a district shall
be changed so as to transfer an area from one district to another
district of a different classification, the provisions of this chapter
shall also apply to any nonconforming uses existing therein or created
thereby.