Terms For Roof Truss Members

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.

Terms for roof truss members.

There are two main types of timber roof trusses. The uppermost point of a truss. The same roof has a 4 12 or 1 3 pitch. Truss members form a series of equilateral triangles alternating up and down.

In historic carpentry the top chords are often called rafters and the bottom chord is often referred to as a tie beam. 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. Truss members are made up of all equivalent equilateral triangles. Roof cap the total roof assembly members located above the wall line such as beams trusses plates purlins decking bridging ceiling roofing etc.

A roof truss consists essentially of the following components. 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. 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. 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.

The following diagram shows the terms applying to gable end roofs. I upper chord members. The terms pitch and slope are simply two different ways of expressing the same measurement. 4 2 design is used for shallow floor trusses.

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. A metal plate connected wood truss is a roof or floor truss whose wood members are connected with metal connector plates. Hangers connect carried trusses to the carrier or girder. A percentage increase in the stress permitted in a member based on the duration of the load causing the stress acts on the member.

A horizontal or inclined member that establishes the lower edge of a truss usually carrying combined tension and bending stresses. A roof s slope is the number of inches it rises for every 12 inches of horizontal run a roof with a 4 in 12 slope rises 4 inches for every 12 inches of horizontal run. Components of a steel roof truss.