Nothing in this chapter shall prevent the restoration or continuance of a nonconforming building or structure which is nonconforming because of its use and which is partially destroyed by fire, explosion, act of God, or of any public enemy, or the like, if the extent of the destruction be not more than 50% of the true value based upon assessed value of the whole building or structure at the time of the partial destruction. If, however, any such building or structure shall be destroyed in the manner aforesaid to an extent exceeding 50% of true value of the whole building or structure at the time of the destruction, then the same may only be reconstructed and thereafter used in such a manner as to conform to all the requirements, terms and conditions of this chapter.