TERMINOLOGY GLOSSARY

We've assembled an exhaustive glossary of truss-related terms to make the world of trusses easier to understand.

Bearing - A structural support for a truss. Usually a wall, hanger or beam.

Bottom Chord - A horizontal or inclined member, establishes the lower edge of a truss.

Butt Cut - A slight vertical cut at the outside edge of a truss bottom chord to insure a uniform span. Usually 1/4 inch.

Cantilever - Extension of the bottom chord beyond its support. Excluding the overhang.

Concentrated Load - The superimposed load centered at a given point.

Dead Load - Any permanent load such as the weight of roofing, sheathing, insulation or ceiling material, as well as the truss itself.

Deflection - Downward vertical displacement of a truss (when in place, due to dead and live loads).

Design Loads - The live and dead loads which a truss is engineered to support.

Drag Strut - Typically a horizontal member, such as a truss or beam, which transfers shear from a diaphragm to a shear wall.

Dropped Gable - A gable truss that has its top chord lowered vertically to allow outlookers or a gable ladder to, for an overhang.

Engineer Certified Drawings - A truss where loading, size and grades of material are called out and detailed and a certified engineer’s seal is affixed to that drawing.

Gable End - A truss with vertical studs, usually spaced at 16” o.c., The gable usually sits on an end wall and the studs help to provide support for the sheathing and resistance to wind.

Girder Truss - Usually a multiple-ply truss designed to carry over an opening or support other trusses.

Heel - The point on a truss at which the top and bottom chords meet.

Hip Set - A trussed system where three planes come in on a slope.

Joint - See panel point.

Lateral Bracing - A member installed and connected at right angles to a chord or web member of a truss to resist lateral movement.

Live Load - Any loading which is not of permanent nature, ie. snow, wind.

Overhang - The extension of the top chord of a truss beyond the heel, measured horizontally.

Panel Length - The centerline distance between joints measured along the chord.

Panel Points - The point where a web or webs intersect at a chord.

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

Permanent Bracing - Bracing put on a roof system that is intended to remain permanently on the roof to reinforce the structure.

Piggyback - A cap truss provided which will sit on top of the trusses below ( with purlins and blocking) usually when trusses are too tall to build, or too tall to deliver.

Pitch - Inches of vertical rise for each 12 inches of horizontal run.

Plumb Cut - Top chord end cut to provide for vertical (plumb) installation of fascia.

Purlin - A horizontal member attached to and placed perpendicular to the truss top chord to support the roofing.

Ridge - A ridge is the line formed when two planes meet, usually at truss peaks.

Shop Drawings - Detailed drawings of a truss showing critical dimensions such as span, overhang, slope, etc.

Slope - See pitch

Spacing - The centerline distance between trusses, ie. 24” o.c.

Span - The length of the truss, measured from outside bearing to outside bearing, except in the case of cantilever conditions. If the truss is cantilevered beyond an outside bearing, the span length would include the length of the bottom chord beyond the outside wall.

Splice Points - Top and bottom chord splice. The point at which two chord members are joined together to form a single member.

Stub - When the truss is held back from its original span.

Temporary Bracing - Bracing added to the roof or floor system to brace it during erection and installation.

Top Chords - An inclined or horizontal member that establishes the upper edge of a truss.

Truss - A manufactured component that functions as a structural support member. A truss employs one or more triangles in its construction.

Valley Set - Trusses which set in a perpendicular direction on top of other trusses to form a ridge.

Webs - Members that join the top and bottom chords to form triangular patterns that give the truss strength.