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Roof trusses

Bottom chord

The bottom chord is the lower member of a truss that ties the two ends together and usually carries the ceiling.

Also known as bottom chords, tie, tie beam, ceiling tie, lower chord

The bottom chord (often called the tie) stops the top chords from spreading the walls apart. In a standard truss it works mainly in tension, and it also carries the ceiling boards, insulation and any loft storage above it.

It is usually horizontal, but scissor, cambered and raised tie trusses shape or lift the bottom chord to create a higher or sloping ceiling.

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
Top chordThe top chord is the upper, usually sloping member of a truss that forms the roof slope and carries the roof covering. Web (truss web)Webs are the internal members of a truss that connect the top and bottom chords and divide the truss into triangles. Scissor trussA scissor truss has a sloping bottom chord, so the ceiling underneath can follow the roof and form a vaulted room.
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