The consultant may also review plans that include the modification of the exterior design features of an existing structure which involves a change in the exterior materials in existence on such structure. "Modification of the exterior design features," as used herein, includes but is not limited to the addition, deletion or modification of surface materials (masonry, wood, brick, stucco), windows, doors, overhangs, porches, porticos, chimneys, outdoor public space, cornices, etc.