Scissor Truss Calculator
A scissor truss is a roof truss where the bottom chord slopes upward toward the ridge instead of running flat, creating an open, vaulted ceiling below without removing the truss's structural triangulation. Enter your span and pitch below to size a scissor truss and get rafter length, ridge height, and material cost.
Size Your Scissor Truss
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What Is a Scissor Truss Used For?
A scissor truss gets its name from the way the two bottom-chord members cross like scissor blades when viewed from the side, each sloping up from the wall plate toward a point below the ridge. This lets a room have a vaulted or cathedral ceiling while the truss itself still carries roof loads down to the exterior walls — no interior load-bearing wall or exposed ridge beam required.
Because both the top chord and bottom chord slope, a scissor truss needs deeper web members and more careful connector-plate engineering than a standard gable truss with a flat bottom chord. The vertical distance between the two chords (the "scissor depth") controls how open the vault feels inside; a steeper bottom-chord slope gives more ceiling height but increases member forces.
Scissor trusses are common in great rooms, churches, and additions where a cathedral ceiling is wanted without stick-framing a full rafter-and-ridge-beam roof. Always confirm scissor depth and web layout with a truss manufacturer's engineered drawing — the geometry is sensitive to even small changes in pitch.
Frequently Asked Questions
What is the difference between a scissor truss and a regular truss?
A standard (common) truss has a flat, horizontal bottom chord, giving a flat ceiling below. A scissor truss slopes the bottom chord upward too, so the ceiling follows a vaulted line while the truss still spans the full building width.
How much does a scissor truss cost compared to a standard truss?
Scissor trusses typically cost 15-30% more than an equivalent standard truss because the sloped bottom chord and deeper web bracing require more lumber and more engineering per truss.
Can a scissor truss span the same distance as a gable truss?
Yes, with the correct engineering — but because the bottom chord carries more bending force than a flat-chord truss, scissor trusses often need larger members or closer spacing at the same span.