Types of Timber Trusses

King Post Truss

• A king post truss consists of a vertical king post that joins the center of the tie beam to the ridge of the rafters. Angled struts are usually used as additional members to join the king post and the rafters. The king post truss is an example of a closed truss.

Queen Post Truss

• A queen post truss consists of two vertical queen posts that are joined at equal distances from the center of the tie beam to the rafters. They are also connected by a horizontal member at the heads. This truss can span greater widths than a king post truss.

Pratt Truss

• A Pratt truss consists of a number of vertical posts between the tie beam and the rafters. They are joined with angled struts between them, with the angles in the same direction as the rafters. A north light truss is a mono pitch variation of a Pratt truss.

Howe Truss

• Howe trusses have a similar configuration to the Pratt truss, with the angles in the opposite direction to the rafters. Parallel and metal versions of these trusses were extensively used in bridge building.

Scissor Truss

• A scissor truss is similar to a king post truss, with the tie beam replaced by two angled members that meet the rafters. This allows for additional height in the center of the room and creates a pitched internal ceiling. This truss needs additional support at the walls because it has a natural tendency to spread out without a tie beam. This is an example of an open truss.

Hammer-Beam Truss

• A hammer-beam truss eliminates the middle sections of the tie beams and horizontal members to form an internal stepped profile. The volume of the space created is one of grandeur and has been used in buildings such as cathedrals and great halls. The truss is supported by external structures called buttresses to counteract the lateral forces of the truss.