What is the term for a structural element placed horizontally across the top of door and window openings to support the walls above?

The term for the structural element placed horizontally across the top of door and window openings to support the walls above is known as a "Header." A header is designed to carry the load of the wall above it, effectively distributing weight to the vertical framing elements on either side of the opening. This function is crucial in maintaining the integrity and stability of the building structure, as it prevents sagging or other structural failures that could result from load stress around door and window openings.

Headers can be made from various materials, including wood, steel, or engineered wood products, and their size and design depend on the load they need to support. Understanding the role of a header is fundamental in both construction and assessment practices, ensuring that structures are safe and within building codes.

The other terms refer to different structural components. A sill typically refers to the horizontal piece at the bottom of a window or door frame, the lintel is often used interchangeably with header but can specifically refer to a support beam above openings in masonry structures, and a beam is a general term for any horizontal structural member that supports vertical loads.