A truss is a structural framework built from triangulated members, typically connecting a top chord, bottom chord, and diagonal web members, engineered to efficiently span distances while using less material than an equivalent solid beam would require for the same span.
This triangulated geometry is fundamentally efficient because triangles maintain their shape under load without relying on rigid joint connections the way a simple rectangular frame would need.
Trusses are manufactured off site under controlled conditions and delivered to a job site as complete, engineered assemblies, offering consistent quality and often faster installation than comparable site-built framing.
What Does a Truss Involve?
- Top and bottom chords defining the truss’s overall shape
- Diagonal web members creating triangulated stability
- Metal connector plates joining members at each intersection
- Engineering specific to the required span and load
Why Are Trusses Important?
The material efficiency triangulation provides allows trusses to achieve longer spans using less lumber than equivalent solid beams or rafters, while their off-site manufacturing offers consistent engineering and often faster on-site installation than comparable site-built framing. This combination of efficiency and speed has made trusses the dominant choice for most modern residential roof framing and increasingly for floor systems as well.
Because trusses are engineered as complete assemblies for specific applications, field modification, like cutting a truss to accommodate an unexpected condition, is generally prohibited without manufacturer or engineering approval, since even minor unauthorized changes can seriously compromise the truss’s intended structural performance. This standard practice protects the substantial engineering investment built into every truss. This reliability is a major reason trusses dominate so much of modern residential construction today.
Truss vs. Rafter
A truss is a factory-engineered, triangulated assembly manufactured off site. A rafter is a single, solid structural member cut and installed individually on site, offering more field flexibility but generally requiring more labor than installing prefabricated trusses.