Roof Truss Member Dims

The answer is a convention of the truss producing industry.

Roof truss member dims. So for example a dimension string that reads. Down to avoid putting undue strain on the truss members. Closed in which the bottom chord is horizontal and at the foot of the truss and open in. B check the truss layout to identify the trusses and also.

This stands for f eet i nches s ixteenths. 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 in historic carpentry the top chords are often called rafters and the bottom chord is often referred to as a tie beam there are two main types of timber roof trusses. The buckling resistance is obtained from bs en 1993 1 1 by applying a reduction to the resistance of the cross section. A check dimensions of the supporting structure prior to manufacture.

A roof truss layout must be obtained prior to erection with the following points considered. In most truss members only flexural buckling of the compressed members in the plane of the truss structure and out of the plane of the truss structure need be evaluated. 4 7 12 would be the dimension 4 7 12 16 or 4 7 3 4. Just remember the acronym.

This reduction factor is obtained from the slenderness of the member which depends on the elastic critical force. See sbca s ttb floor truss fact sheet. The important point to keep in mind when you use your truss calculator is that every truss calculation is completely unique and is based on the size of your roof and its specific dimensions.