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Guide to Setting Out & Dimensioning
Support details - Cantilevers
The reaction from the bearing is the greatest load (although upwards) to which a truss is subjected and in order to control excessive bending in the supported chord it is important, except in the smallest trusses, to locate a joint at each bearing. The normal eaves joint illustrated in figure 8a accomplishes this if the “Shift” dimension is less than 50mm, or one-third of the scarf length, whichever is the greater. If the Shift is greater than the allowed a stress check
is required on the short cantilever.

Unfortunately there is usually insufficient space for an additional web so should the check fail, as it often does, it is necessary to increase the size of the bottom chord or alternatively incorporate a relief rafter, (as
shown in figure 10b) or a heel wedge. Both of these options can add to the final cost of the truss and therefore it is best to avoid cantilevers in this range.
If the “Shift” is greater than two scarf lengths, then a standard cantilever truss as show in figure 10a is employed. The chord sizes are usually no greater than the corresponding non-cantilevered standard truss and the cost is little more. Many variations are possible by adjusting the position of a joint of a noncantilevered standard truss type so that it is over a bearing. Finally, if required, a non-standard cantilever truss of almost any triangulated configuration can be designed and fabricated. Note that a brace may sometimes be required on the bottom chord which is untypically in compression.