A door header is a support which is built in above a door, and it may be known simply as a “header.” Windows also have headers. Classically, a door header is about twice as thick as the surrounding framing, and it is supported by the king studs, another integral component of door and window framing. Headers are important for structural integrity, and they are required by law in many regional building codes. The term “header” is also used to describe ornamental molding positioned over the top of a door.
When doors and windows are framed, extra reinforcement is required. There are two reasons for this. The first is that doors and windows are points of structural weakness, because studs must be omitted or moved to accommodate the opening. The second is that doors and windows place strain upon a structure as they are used. Doors in particular are weak points, as the opening and shutting of a door puts strain on the surrounding framing.
Many building codes have specific regulations about how doors should be framed. King studs are run along the side of the frame to provide support and take some of the weight and strain of the door, and the door header bridges the top of the door, supported by the king studs. Some door headers are solid beams which have been chosen for their thickness, while others are made by attaching several pieces of lumber.
Average individuals never see the door header, because it is hidden under the walls, along with the rest of the framing of the house. Door headers can become an issue during renovations, as older homes may have smaller and therefore weaker headers, and headers are at risk of rot, just like other framing components. A contractor may recommend that the door and window headers be replaced when doors and windows are replaced, even if the framing does not need to be redone to accommodate a new door or window.
In the decorative sense, headers run along the tops of doors to make them more visually interesting. Headers are usually made from wood or plaster molding, and they may vary from relatively restrained classical designs to elaborate friezes, depending on the look and feel of the house. Ornamental door headers are typically easy to replace, and changing the ornamental headers can be a great way to change the look of a room without spending a great deal of money on remodeling.