(A)   To avoid undue hardship nothing in this chapter shall be deemed to require a change in the plans, construction, or designated use of any structure, including a sign, for which a building permit was lawfully applied for prior to the effective date of adoption or amendment of this chapter and upon which actual construction has been carried on and completed within two years of said effective date.
   (B)   To avoid undue hardship, nothing in this chapter shall prevent the restoration of a structure wholly or partly destroyed by fire, explosion, amendment of this chapter, or prevent the continuance of the use of such building or part thereof as such use existed at the time of such destruction or prevent a change or expansion of such existing use as provided in this chapter.
   (C)   On any nonconforming structure or portion of a structure containing a nonconforming use, work may be done on ordinary repairs, or on the cubic content existing when it became nonconforming shall not be increased.  Nothing in this section shall be deemed to prevent the strengthening or restoring to a safe condition of any building or part thereof declared to be unsafe by any official charged with protecting the public safety, upon order of such official.
('65 Code, § 1352.03)