A scissor truss is a specialized roof truss design where the bottom chord slopes upward from each end toward the center, rather than remaining level, creating a vaulted or cathedral ceiling effect on the interior while still maintaining the structural efficiency of a prefabricated truss system.
This design achieves the visual openness of a cathedral ceiling without requiring the more complex structural ridge beam and post support system that a true cathedral ceiling built with rafters alone would need.
Because the sloped bottom chord creates a different geometry than a standard truss, scissor trusses generally require deeper overall dimensions and more careful engineering to achieve the same span as a comparable standard truss.
What Does a Scissor Truss Involve?
- A sloped bottom chord creating the vaulted interior shape
- A standard sloped top chord matching the exterior roof pitch
- Engineering accounting for the more complex load path
- Typically greater overall depth than a standard truss
Why Are Scissor Trusses Important?
Scissor trusses offer a way to achieve the architecturally desirable vaulted ceiling look using standard prefabricated truss technology, avoiding the more expensive and complex ridge beam and post system that a traditional cathedral ceiling design would otherwise require. This makes the vaulted look considerably more accessible and cost-effective for many residential projects than it would be using conventional rafter framing alone.
Because the interior slope differs from the exterior roof slope, the resulting attic space between the two chords is typically limited and irregularly shaped, making it less useful for storage than the space above a standard truss with a level bottom chord.
Scissor Truss vs. Attic Truss
A scissor truss creates a vaulted ceiling shape by sloping the bottom chord upward. An attic truss instead uses a modified web configuration to leave open, usable floor space within the truss’s interior for storage or finished living space, a different design goal entirely.