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