What is the term for a horizontal structural member installed above a door or window?

The term for a horizontal structural member installed above a door or window is commonly referred to as a lintel. A lintel serves several important functions in construction, primarily providing support to the structure above openings such as doors and windows. This structural member helps to distribute the weight of the material above the opening across the adjacent walls, preventing failure of the structures due to gravity and other forces. Lintels can be made from various materials, including wood, steel, or concrete, depending on the load requirements and design of the building.

While headers are also horizontal members, they are typically associated with framing in walls surrounding doors and windows, particularly in residential construction. Beams and trusses are larger structural elements used in various applications for carrying heavier loads across broader spans or supporting roofs, but they are not specifically designated for openings like doors or windows. Understanding the distinct roles of these structural elements is crucial in recognizing the proper terminology used in construction contexts.