No lot, building or structure that is lawfully nonconforming with respect to any area requirement, including, without limitation, height, minimum yard size or minimum lot area per family, shall be enlarged or altered in such a manner as to increase the nonconformity or so as substantially to enlarge or increase the habitable or other useful area of the nonconformity, including, without limitation, the alteration of roof or floor levels or the addition of habitable or other useful area above or below a lawfully nonconforming building or structure.