The term “architrave” is used in two different senses in the architecture community. In the original sense, an architrave is part of the entablature used on the exterior of a structure as a decorative element. In the modern sense, architraves are the molding which surrounds doors and windows on the inside. Like other molding, they are purely ornamental in this sense, designed to make interior spaces more visually appealing and interesting.
The original architrave is located at the bottom of an entablature, resting right on top of the columns. It might be decorated in a number of ways with carvings, or left plain, depending on the type of design involved. This type of architrave is seen in Greek and Roman-influenced design, sometimes called “Classical Architecture,” in which columns are extremely common. The entablature forms an important structural support in addition to serving an ornamental function, and is often decorated as a whole with friezes, carvings, and so forth.
When talking about interior architraves, people are discussing the molding used to surround doors, windows, and other openings. Also known as casing, architraves are used to add visual interest and to soften the edges of an opening. They are used in a variety of architectural styles, and can vary in complexity. Many are painted in contrasting trim or made from naturally beautiful woods so that they stand out from the surrounding walls.
Architraves are placed after the window and all of the framing have been installed. It is possible to add architraves when none were installed originally, for people who want to create more visual interest in a room, without too much fuss. Many companies make standardized versions which can be quickly cut down to the desired size and installed in an afternoon. People can also replace existing architraves if they become damaged or clash with the décor or architectural style of a room.
Not all rooms are suited to architraves. These decorative features show up 19th century and early 20th century architecture, when buildings had more ornate, fussy interiors. In some cases, the architraves can also include rails and other fittings for displaying art and hanging window treatments such as sheers or drapes. They can look odd in architecture from other periods; a Midcentury Modern home, for example, could look decidedly peculiar with architraves, and may be more suited to less ornamented casings or to no internal molding at all.