Sec. 35.03. - Alteration, reconstruction, etc., of nonconforming buildings.

Except in cases where a use permit is approved, no existing building designed, arranged or intended for or devoted to a use not permitted under the regulations of this ordinance for the district in which such building or premises is located shall be enlarged, extended, reconstructed or structurally altered, unless such use is changed to a use permitted under the regulations specified by this ordinance for such district in which said building is located; provided, however, that authorized maintenance shall be permitted not exceeding a total amount, during a period of five years, or fifty percent of the assessed value of the building according to the assessments thereof by the assessor of the city.