King Post

Definition

A king post is a vertical member in a roof system, placed between the center of the horizontal tie beam and the ridge or apex of the inclined rafters. It is often used in specific types of fabricated trusses.

Purpose

The purpose of the king post is to provide structural support to the roof by transferring the load from the ridge to the tie beam, thereby preventing the rafters from spreading and the roof from sagging. It is a crucial component in truss systems for maintaining the integrity and stability of pitched roofs.

Examples of Use

1. Traditional Timber Roofs: In traditional timber-framed buildings, king posts are used to support the central point of the roof.
2. Modern Truss Designs: In modern construction, fabricated trusses with king posts are used for their strength and efficiency in spanning wide spaces without intermediate supports.
3. Historical Restoration: King posts are often seen in the restoration of historical buildings, maintaining the original structural design.

Related Terms

• Tie Beam: A horizontal beam that ties together two opposite walls and prevents them from spreading apart.
• Ridge Beam: The topmost horizontal beam in a roof structure, to which the upper ends of the rafters are attached.
• Queen Post: A pair of vertical posts in a roof truss, supporting the rafters and spanning between the tie beam and the top chord.

Notes

King posts must be correctly sized and installed to effectively bear the loads placed upon them. They are commonly used in various truss designs, including simple king post trusses and more complex configurations.