Howe Truss Calculator
A Howe truss arranges its diagonal web members to carry compression and its vertical members to carry tension — the reverse of a Pratt truss — making it well suited to heavier roof and bridge loads where compression members can be kept short. This calculator sizes a Howe-style truss from span and pitch.
Size Your Howe Truss
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How the Howe Truss Carries Load
In a Howe truss, the diagonal web members slope toward the center of the span and carry compression, while the shorter vertical members carry tension. This arrangement was historically favored for timber construction, since timber resists compression well and the compression diagonals could be kept relatively short and stocky.
Method-of-joints analysis on a Howe truss shows load flowing from the top chord down through the diagonal compression members toward the supports, with the verticals tying the top and bottom chords together in tension — the opposite force pattern of a Pratt truss's tension diagonals and compression verticals.
Howe trusses are commonly specified for heavier roof loads, wider spans, and structures originally built with timber diagonals and steel (or iron) vertical tension rods, a hybrid detail still referenced in some engineered wood truss designs today.
Frequently Asked Questions
What is a Howe truss?
A Howe truss is a triangulated truss where the diagonal web members carry compression and the vertical members carry tension — a layout historically favored for timber construction because timber performs well in compression.
What is the difference between a Howe truss and a Pratt truss?
The two are mirror opposites in force distribution: a Howe truss puts diagonals in compression and verticals in tension, while a Pratt truss puts diagonals in tension and verticals in compression.