Roof Truss Bottom Chord

Those trusses were engineered with a heavy critical dependency on the bottom chords which are in tension.

Roof truss bottom chord.

The horizontal beam of the triangle of a bottom chord is used in this simple triangle truss construction. Roof truss uplift occurs when the bottom chord of the truss is exposed to significantly different moisture or temperature conditions than the rest of the roof truss. It is utilized in a framed roof comprised of rafters and a ceiling joist. Removal has left them extremely vulnerable to collapse due to spreading especially under snow loads but also under just the load of the roof itself.

In standard heel applications of roof trusses the bottom chord is cut on each end at an angle consistent with the roof pitch of the truss. The roof system is basically a hinge now. And the responses from the experts and my take on each one. The trusses are 42 long with a 2x10 bottom chord 3 12 pitch.

The stability of this shape supported by the bottom chord is the reason for the common usage of the triangle truss. For example if the bottom of the truss is buried in insulation while the remainder is in the open attic air this condition can occur.