No permit is required for the construction of any fence or wall which is four (4') feet or less in height. Any fence or wall which exceeds four (4') feet in height and is more than 10% solid shall be set back from any property line a distance of at least one (1') foot unless the fence or wall is required to screen off-street parking areas as required in Section 34-13 of this chapter. No fence or wall shall exceed six (6') feet in height provided, however, necessary retaining walls may exceed six (6') feet in height after a site plan has been reviewed and approved by the Borough Planning Board. Fencing enclosures of public utilities are exempted from the regulations of this subsection.