kingpost

A king post is a central vertical member in a king-post roof truss, a type of timber roof truss used in traditional architecture. In a typical king-post truss, a tie beam spans the width of the building at the base of the roof. Two principal rafters run from the ends of the tie beam up to meet at a central apex above the midspan. A king post—a vertical member—extends from the apex down to the midpoint of the tie beam. The assembly forms two triangular panels on either side of the post. The load path carries roof loads from the rafters to the apex, then down the king post to the tie beam and wall supports. The tie beam resists horizontal thrust, while the king post helps transfer the load and keeps the rafters in compression. Variants may include additional struts or braces to stiffen the structure.

Historically, king-post trusses were common in medieval Europe and widely used in English and continental timber framing for small-to-mid-span roofs. They remained common in barns and houses through the 18th and 19th centuries and have continued in traditional timber framing and in some lightweight modern applications, including timber roofs and mass timber assemblies.

Compared with a queen post truss, a king-post truss uses a single vertical post rather than two, resulting in a simpler and often more economical construction suitable for shorter spans. Etymology traces the name to the central king post; the concept appears in various forms across cultures.