No existing building or land designed, arranged or intended for or devoted to a use not permitted under the regulations of this Code for the district in which such building or land is located shall be enlarged, extended, reconstructed or structurally altered unless such building and such enlargement, extension, reconstruction and structural alterations and further use hereof conform in every respect with the regulations specified by this ordinance for such district in which said building or land is located, provided nothing herein shall prohibit any reasonable repairs or alterations in a building or land used for such existing purposes.