A rafter is an individual sloped structural member, cut and installed on site rather than prefabricated, spanning from the wall top plate up to the ridge, forming the traditional structural skeleton of a roof before prefabricated trusses became the dominant modern method.
Unlike a truss, which arrives as a complete engineered assembly, each rafter is individually measured, cut, and installed by carpenters directly on the job site, offering more flexibility to adjust for specific site conditions or design changes.
While trusses have largely replaced rafter framing in typical residential construction, rafters remain common for smaller structures, additions matching existing rafter framing, or situations requiring the specific flexibility site-built framing provides.
What Does Rafter Framing Involve?
- Individual lumber cut to the specific roof pitch and span
- A birdsmouth cut where the rafter meets the wall plate
- Connection to the ridge board or beam at the peak
- Ceiling joists or rafter ties resisting outward thrust
Why Are Rafters Important?
Site-built rafter framing offers genuine flexibility to adjust for unexpected site conditions or last-minute design changes that a prefabricated truss, engineered and manufactured off site to fixed dimensions, simply can’t accommodate as easily. This adaptability remains valuable for additions needing to match existing roof framing or complex custom designs where standard truss configurations don’t quite fit.
The tradeoff for this flexibility is generally more labor and time compared to installing prefabricated trusses, along with more reliance on the individual carpenter’s skill and the accuracy of on-site calculations rather than factory-verified engineering. This tradeoff between flexibility and efficiency continues to shape which method suits a given project best.
Rafter vs. Truss
A rafter is an individual structural member cut and installed on site. A truss is a complete, factory-engineered assembly delivered ready for installation, generally offering faster construction and more consistent engineering than comparable site-built rafter framing.