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Roof trusses

Top chord

The top chord is the upper, usually sloping member of a truss that forms the roof slope and carries the roof covering.

Also known as top chords, truss top chord, principal rafter, upper chord

In a pitched truss the two top chords run from the heels up to the apex and give the roof its pitch. They carry the weight of the roof covering, battens and snow, and they work mainly in compression, with bending between the joints where the webs support them.

Top chord size and grade are set by the truss design. On long or heavily loaded trusses the chord is supported at more points by extra webs, as in a fan truss.

Apex (ridge) Nail plate Top chord Web Bottom chord Heel Overhang Span
The parts of a typical fink (W) roof truss. Every joint is held by a nail plate.
Related terms
Bottom chordThe bottom chord is the lower member of a truss that ties the two ends together and usually carries the ceiling. Web (truss web)Webs are the internal members of a truss that connect the top and bottom chords and divide the truss into triangles. Roof trussA roof truss is a prefabricated triangulated timber framework that supports a roof and spans the space between external walls.
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