Door casing is a type of trim or molding used around a door opening or frame. It can serve a functional or aesthetic purpose, or both. Aesthetically, door casing helps blend the door opening in with the surrounding wall. It can also be used as a focal point in the room's decorating scheme. Functionally, door casing helps to hide the gap between the frame and the wall on either side while covering up insulation or other materials installed within the wall cavity.
In some homes, door casing is chosen to match other types of trim, including baseboards, crown molding or chair rail. In others, the door casing may be the only trim used in the room. Generally, door casing is smaller and plainer than other types of molding, though it can also be quiet elaborate in some cases.
There are many different types of casing available for doors, and each type can vary based on material, design, finish or profile. Like all molding, door casing is made from medium-density fiberboard (MDF), solid wood, aluminum or vinyl. It can be painted or stained during installation or pre-finished by the manufacturer. Some casing is built-in to the door frame itself, while other types are added separately after the door and frame are installed. Some trim is designed only for interior use, while other casing can be used both indoors and out.
One of the best ways to differentiate between different types of door trim is to compare the profile, or design of each unit. The simplest types of casing have a square or rectangular shape, while others are rounded or oval. Some wood casing is carved with elaborate designs and profiles, and handy woodworkers can even carve their own designs into wood to personalize their door casing.
These profiles and materials give the casing different looks that complement various types of décor. Sleek, rounded trim is often used in homes with modern or sparse decorating schemes, while elaborately designed casing works better in more traditional or Victorian decors. Different types of casing can even be combined together to create a whole new look that's unique to the homeowner.
The most basic door casing consists of simple molding around three sides of the door frame. With more complex casing, the vertical members may be thicker or wider. These larger types of vertical casing are known as “pilasters,” and may feature traditional Greek or Roman column designs. At the top of the frame, some homeowners choose larger panels instead of smaller sections of casing. These panels are known as “plinths,” and often feature intricate designs or a series of rosettes.