Cornices are mostly found in old Victorian homes that used cornices as a decorative border around the ceiling to enhance the beauty of a home. Though the moldings are exquisite, they are rarely found fully intact. Modern versions of those Victorian embellishments are implemented into newer homes. Repairing cornices, whether they are old or new, depends on the detail of the cornice. The more elaborate the design, the more difficult it will be to restore.
5 Use a wood block to help achieve a straight edge when mimicking the cornice's shape and dimensions with plaster.
Apply plasterboard adhesive into the gap with a taping knife.
Sand down any parts of adhesive that stick out over the cornice.
Sand the area after it has dried. Wipe clean with a damp sponge. Paint over the repaired section.