General Info

In this section you will find some general truss tips. Click the arrows on the bottom of each page to navigate.

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Compute Rafter Length

Match New to Existing Roof

Order Specify


To order specify

  1. Quantity of trusses required at desired spacing, or building size.
  2. Length of truss
  3. Span of truss
  4. Type of truss (i.e. common, scissor, etc.)
  5. Length of cantilever or overhang or both.
  6. Pitch desired (specify total height if pitch is not known)
  7. Size of bearing walls
  8. Cut at end of top chord (plumb, square, level)
  9. Design load requirements
  10. Location of jobsite (provide written directions)

Terms & Definitions


Top chord (T.C.) = The upper member (Rafter) of the truss.

Bottom Chord (B.C.) = The lower member (Ceiling joist) of the truss.

Webs = All interior members of the truss.

Pitch or Slope = Rise (in inches per foot) of the chord(s)

Length = Total measure of the bottom chord of the truss.

Out-to-out span = Distance from outside of left supporting wall to the outside of right supporting wall.

Interior bearing = Any wall between the outside supports which will be used to help support the truss (not partitions).
NOTE: Interior bearings should be located by the distance to the center of the interior support from the end of the bottom chord.

Overhang (OH) = The measure of the extension of the top chord beyond its intersection with the bottom chord. (Horizontal distance) ** NOT part of the truss length **

Cantilever (Cant.) = The measure of the extension of the bottom chord (entire truss) beyond the support wall. ** This is a part of the truss length **

Gable End = Non-structural truss with webs replaced by vertical 2x4's at 24" o.c. (16" o.c. by request). Louvre openings available. 

Dropped Gable = Gable with top chord lowered to support outriggers. Specify size of outriggers. 

Cut = The angle at which the end of the top chord is trimmed.

  • Plumb = vertical with ground
  • Square = perpendicular to the top chord slope
  • Flat = parallel with ground