Normal maintenance and repair, structural alteration in and moving, reconstruction or enlargement of a building which does not house a nonconforming use, but is nonconforming as to the zone regulations for lot area, lot width, front yard, side yard, rear yard, maximum height, maximum lot coverage or minimum livable floor area per dwelling, is permitted if the same does not increase the degree of, or create any new nonconformity with such regulations in such building.