A cornice is any type of horizontal molding that crowns a building or a portion of a home (door or window). Ultimately, it is a box or strip that is placed at the top or on the top of something. Typically, house eaves are sometimes called cornices if they are finished with some type of decorative molding such as crown.
There are three common types of cornices. The first, box cornice, is typically used on most homes. The primary purpose of box (or open) cornice is to push rain water away from a building, which helps to prevent water damage or leaky walls. Box cornices tend to be large, so they need additional support when installed. They also are ventilated to help air circulation within the structure itself.
The next type, the open cornice, has no flat, under-side area of a gutter or soffit. An open cornice is significantly less expensive and makes a building look modern.
The last common type is the close cornice or snub cornice. This type is easy to build, but it doesn’t help direct rain water in anyway unlike the other two types. It works best in warm climates and in buildings that are looking for modern elements and not necessarily a functional design. This type of cornice is a lot less expensive then box ones because they use fewer materials and require less labor. A home contractor can discuss each of the types and determine what type works best for your particular needs.