APB » Roof Trusses » Truss Terminology

Roof Truss Terminology


                  Bottom Chord: A horizontal member that establishes the lower edge of
                   a truss, usually carrying combined tension and bending stresses.

                  Butt Cut: Slight vertical cut on the outside edge of truss bottom chord to make sure uniform nominal span.
                   (Typically 1/4 inch)

                  Cantilever: A condition where both the top and bottom chords extend beyond a support structure with
                   no bearing  at the extended end.

                  Chase Opening: An open panel in a floor truss for used for running utilities through it such as
                   air conditioning  or heating ducts.

                  Clear Span: The horizontal distance between interior edges of support.

                  Concentrated Load: Superimposed load centered at a given point; (like roof mounted air conditioners).

                  Dead Load: Any permanent load such as the weight of the truss, sheathing, or purlins, roof material,
                   ceiling, etc.

                  Deflection: Movement of an in place truss caused by dead and live loads.

                  Design Loads: The live and dead loads which a truss is designed to support.

                  Fascia: Dimensional lumber used as trim board applied to ends of overhang.

                  Heel: The point on a truss where the top and bottom chords intersect.

                  Heel Height: Height of truss at end of span (excluding overhangs) or plumb cut & butt cut.

                  Interior Bearing Truss: Truss with structural support in the center of a truss span as well as at end points.

                  Lateral Brace: A dimensional lumber member connected at right angles to a chord or web member of a truss,
                   (typically three trusses continuous required).

                  Live Load: Loading which is not permanent, such as snow, wind, temporary
                   construction loads, etc.

                  Overhang: The extension of the top chord of a truss beyond the bearing support.

                  Peak: Point on a truss where the sloped top chords meet.

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

                  Reaction: The total load transmitted to its support by a truss.

                  Sealed Drawings: Structural Drawings or truss drawings having the seal of a
                   registered professional architect or engineer.

                  Slope: (Pitch) The inches of vertical rise in 12 inches of horizontal run for inclined members

                  Square Cut: End of top chord cut perpendicular to the slope of member.

                  Top Chord: The inclined horizontal member that makes up the upper edge of a truss, usually
                   carrying bearing and compression stresses.

                  Uniform Load: A total load that is equally distributed over a given length, usually expressed in
                   pounds per linear foot (PLF).

                  Valley: A depression in a roof where two roof slopes meet.

                  Webs: Members that join the bottom and top chords forming the triangular patterns that give truss
                   action, usually carrying tension or compression stresses.
                  



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