The word "store" as used herein is not intended and shall not be construed to include or permit establishments handling or storing coal, oil, lumber, sand, gravel, stone, brick, terra-cotta, masonry materials, building materials, steel, scrap metal, scrap paper, rags or bulk structural materials or general storage warehouse within a B-2 Business District. However, the storage of materials in connection with the activities of a contractor or similar tradesman may be permitted in the B-2 Business District if such materials are of the finish-type and completely stored inside the building.