No accessory structure or use shall be located in any front yard or in the case where the principal building is set farther back than the minimum depth of the front yard, no accessory structure or use shall be located any farther forward than the front principal building plane as defined herein, except a statue, arbor, trellis, flagpole, residential parking space, garden, unenclosed porch, ground-story bay, chimney, fence, wall, sign or wayside stand, unless explicitly permitted by the regulations in a specific zoning district.