Nothing herein contained shall require any change in the plans, construction or designated use of a building for which a building permit has been heretofore issued, and plans for which are on file with the City Clerk at the time of the passage of this Chapter (September 21, 1964), and the construction of which in either case shall have been diligently prosecuted within one (1) year of the date of such permit, and the ground story framework of which, including the second (2nd) tier or beams, shall have been completed, according to such plans as filed, within two (2) years from the date of the passage of this Chapter (September 21, 1964).

Nothing in this Chapter shall be taken to prevent the restoration within twelve (12) months, of a non-conforming building destroyed to the extent of not more than seventy-five percent (75%) of its replacement value (exclusive of foundations) by fire, explosion or other casualty, or act of God, or the public enemy, provided that when such restoration becomes involved in litigation, the time required for such litigation shall not be counted as a part of the twelve (12) months allowed for reconstruction; and nothing in this Chapter shall be taken to prevent the continued occupancy or use of such building or part thereof which existed at the time of such partial destruction, but any building so damaged more than seventy-five percent (75%) of its value may not be rebuilt, repaired, or used unless it is made to conform to all regulations for buildings in the district in which it is located.

The determination of whether a building or structure is seventy-five percent (75%) destroyed shall rest with the Building Inspector and the Board of Aldermen.

The provisions of this Chapter shall not apply to prevent the extension of any building, existing in any district at the time of the adoption of this Chapter (September 21, 1964), to the height to which the walls, foundations and framework of such existing building originally were intended, designed, and constructed to carry; provided however, that the actual construction of the extensions in height permitted by this Subsection shall have been duly commenced within ten (10) years from the date of the adoption of this Chapter (September 21, 1964).