(A) A certificate of appropriateness issued by the Commission, shall be required before the construction or demolition, or moving of any building or structure or part thereof within the District that is or will be visible from a public way. A certificate of appropriateness issued by the Commission for an extension, alteration or repair which does not constitute a construction or demolition shall be required whenever the Building Inspector, within his or her discretion, determines that a building or structure will be altered, extended or repaired in a manner as to produce a major change in exterior appearance of the building or structure.
(B) A major change includes, but is not limited to the enclosure, addition or removal of a porch; the alternation of a roof line; the addition of a dormer, canopy or room; the addition of siding; the removal or addition of decorative trim; and any significant alternation, extension or repair which would result in either excessive similarity or dissimilarity of design in relation to any other building or structure or for which a permit has been issued within a distance of 1,000 feet of the proposed alternation, extension or repair which would result in inappropriateness of design and building materials in relation to the aesthetic, architectural or historic character of any other building or structure in the District.
(1981 Code, § 39.04)