(A) Ordinary repairs and maintenance of a non-conforming building shall not be deemed an extension of such non-conforming building and shall be permitted.
(B) No structural alteration shall be made in a building or other structure containing a non- conforming use, except in the following situations:
(1) When the alteration is required by law.
(2) When the alteration will actually result in elimination of the non-conforming use.
(3) When a building in a residence district containing residential non-conforming uses may be altered in a way to improve livability, provided no structural alteration shall be made which would increase the number of dwelling units or the bulk of the building.
(`92 Code, § 40-6-4)