Roof Trusses

In this section you will find information pertaining to roof trusses. Click the arrows on the bottom of each page to move on to the next page.

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Terms 1

Terms 2

Terms 3

Truss Webbing

Truss Types 1

Truss Types 2


Truss Terms


Bottom Chord - The main member of a truss running along its lower side between supports and usually carrying combined tension and bending.

Cantilever - The condition where both top and bottom chords extend beyond a support with no bearing at the extended point.

Chase Opening - Also called "duct opening", is a square or rectangular shape, free of diagonal web, usually positioned at or near the center of a flat truss.

Clear Span - Horizontal measurement between the inside faces of two bearings or supports.

Heel - The point on a truss at which the top and bottom chords intersect, usually occuring at support.

Level Return - A horizontal member of the truss running from the end of the overhang back to the outside of the wall to form a soffit.

Nominal Span - Horizontal distance between outside edges of supports.

Overhang - The extension of a top chord or bottom chord of a truss beyond a support.

Overall Truss Length - The horizontal length of a truss including the cantilever, but not the overhang.

Panel Point - A point at which one or more web members intersect the top or bottom chord.

1/3 Point - The bottom chord panel point on a Fink truss where webs connect to the bottom chord.

1/4 Point - The panel point on a Fink truss where the webs connect to the top chord, and on a Howe truss, where the webs connect to the top or bottom chords.

Panel Length - The centerline distance measured horizontally between two panel points.

Peak - The point on a truss where the sloping chords meet.

Pitch - The inches, or fraction thereof, of vertical rise in 12 inches of horizontal run for inclined members. Usually expressed as 4/12, 8/12, etc...

Purlin - Horizontal member placed between two main load carrying structural members. They can be used as spacers carrying decking or roofing materials and providing some lateral support for the main members.

Slope - See pitch.

Top Chord - Main members of a truss running along it's upperside supporting the decking and usually carrying combined compression and bending.

Webs - Members that connect top and bottom chords together forming triangular openings to give truss action and usually carrying compression and tension forces.