Preservation ABCs: K is for King Post

Preservation ABCs is a series that will work its way from A to Z, bringing words into conversation that are relevant to historic preservation, whether it’s an idea, feature or vocabulary term. The idea is to help you see preservation everywhere you look and wherever you go. Enjoy! See previous letters.

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K is for King Post (Truss)

Pine Brook Bridge in Fayston, VT: A king post truss bridge. Source: Library of Congress. Click for source.

Pine Brook Bridge in Fayston, VT: A king post truss bridge. Source: Library of Congress. Click for source.

A king post is a type of truss, and can refer to building or bridge construction. Being able to identify a truss is an important part of preservation conversation, whether you are working on an architectural description or talking to a contractor or an engineer. As an introduction to trusses, start with an easy one: the king post truss. It is a simple truss and most often used for short spans. Think of it as a triangle. An easy definition of a king post is borrowed from Cyril Harris’ book, American Architecture: an Illustrated Glossary:

A structural support for a roof formed by two inclined rafters joined at the apex of their intersection. A horizontal tie beam connects the rafters their lower ends, and a vertical central member (called the king post) connects the apex with the midpoint of the tie beam. 

See the triangle? This triangle is a truss and can repeat in bridges (then called multiple king post truss) and structures. They are easiest to identify on covered bridges or metal truss bridges or in attics. Take a look next time your passing over a bridge or hanging around an attic.

Got it? You can always jump to the HAER truss poster and dive right into studying.