Terms For Roof Truss Members

The following diagram shows the terms used for general roof truss members.

Terms for roof truss members.

A percentage increase in the stress permitted in a member based on the duration of the load causing the stress acts on the member. I upper chord members. Roof cap the total roof assembly members located above the wall line such as beams trusses plates purlins decking bridging ceiling roofing etc. 4 2 design is used for shallow floor trusses.

Bearing width the width dimension of the member providing support for the truss usually 3 or 5 bearing must occur at a truss joint location. 4x2 truss has its members have the nominal 2 face up for plate embedment the 4 2 truss is a nominal 4 deep rather than a nominal 2 deep. Saddle a covering on the ridge of the roof so that water will drain. Hangers connect carried trusses to the carrier or girder.

When a roof is to be provided for a building which does not have interior supports and the exterior walls are more than 12 m apart a roof truss will be a convenient arrangement to support the roof. Cantilever that structural portion of a truss which extends beyond the support bearing the cantilever dimension is measured from the outside face of the support to the heel joint. A metal plate connected wood truss is a roof or floor truss whose wood members are connected with metal connector plates. Truss members are made up of all equivalent equilateral triangles.

The same roof has a 4 12 or 1 3 pitch. In historic carpentry the top chords are often called rafters and the bottom chord is often referred to as a tie beam. A horizontal or inclined member that establishes the lower edge of a truss usually carrying combined tension and bending stresses. The following diagram shows the terms applying to gable end roofs.

There are two main types of timber roof trusses. The top members of a truss are known generically as the top chord bottom members as the bottom chord and the interior members as webs. Closed in which the bottom chord is horizontal and at the foot of the truss and open in which the bottom chords are raised to provide more open space also known as raised bottom chord. Components of a steel roof truss.

A roof truss consists essentially of the following components. Truss members form a series of equilateral triangles alternating up and down. The terms pitch and slope are simply two different ways of expressing the same measurement.