Any building or structure which existed at the effective date of this chapter, was nonconforming on such date by reason of its design, its placement on a conforming lot or its location on a nonconforming lot and constituted an otherwise conforming use may be continued. In addition to such right of continuance and the rights accorded under § 210-50, when such building is the principal building on its lot, such principal building may be structurally altered or enlarged, provided that such structural alteration or enlargement does not create any new and further encroachment into any front yard, rear yard or side yard as required by this chapter and does not create a new violation of the terms and provisions of this chapter, and provided further that the provisions of Subsection A of this section shall not be construed to waive the requirements of any other ordinance of the Borough.