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,
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.