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Framing Common Roofscapes
Cantilevered Trusses

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 (figure 34a) accomplishes this if
the bearing shift is less than one-third of the scarf length or is less than 50mm.
If the shift is greater than the allowed a stress check is required on the short cantilever. Unfortunately, there is often insufficient space for an additional web
so it is usually necessary to increase the bottom chord (figure 34c) or alternatively, to incorporate a relief rafter (figure 34d) or a heel wedge. Both of these options can add to the final costs of the trusses and therefore it is best to avoid cantilevering the trusses in this range.
If the shift is greater than two scarf lengths, then an ordinary standard cantilever truss is employed. (fig 35) Note that the chord sizes are not normally greater than the corresponding non-cantilevered standard truss and the cost is very little more. The MiTek system offers many standard cantilevered truss types. Many other variations are possible by adjusting the
position of the joint on a non-cantilevered 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 needed on the bottom chord, which is untypically in compression.