Rafters and prefabricated trusses are two common pitched-roof systems, but the right comparison is project-specific. The choice changes the roof plan, bearing points, bracing, openings, ceiling possibilities, fabrication, delivery, and site sequence. Neither system is automatically longer-spanning, cheaper, faster, or better in every configuration.
Rafters (stick framing)
Rafters are individual sloping members assembled into the roof, usually 2x6 through 2x12 dimensional lumber. Conventional pairs may meet at a ridge board with collar ties, rafter ties, and other bracing, or may be supported by a structural ridge beam; purlins, struts, walls, or other beams may also form part of the designed system. These arrangements are not interchangeable. On a framing plan:
- Individual rafters at a regular spacing, running to the ridge, called out as something like
2x8 RAFTERS @ 24" O.C. - Hip and valley lines where roof planes meet (see gable vs. hip roofs).
- Member, support, tie, bracing, and connection references appropriate to the chosen scheme.
Trusses
Trusses are engineered assemblies, commonly fabricated off site, with webs and chords arranged for defined loads and support conditions. They may span between exterior supports, use interior bearings, or form girders and special shapes. The truss design drawings control. On a placement plan:
- Repeated trusses at a set spacing, commonly 24" on center, labeled by truss type.
- Bearing points, girder or special trusses, openings, orientation, restraints, and bracing references.
- Coordination between the building design, truss design drawings, manufacture, delivery, erection, and permanent bracing responsibilities.
Trade-offs
| Rafters | Trusses | |
|---|---|---|
| Made | On site | Off site, pre-engineered |
| Support | Defined by the rafter, ridge, tie, purlin, wall, and beam scheme | Defined by the engineered truss and building support design |
| Site work | More individual cutting and assembly is common | Repeated placement can be rapid, but delivery, lifting, bracing, and special trusses affect the sequence |
| Ceiling / attic | Can suit open or irregular forms with the right design | Standard, raised-heel, scissor, attic, and other truss forms are possible |
| Design information | Member, tie, support, bracing, and connection design | Truss design drawings plus building-level bearing, anchorage, stability, and bracing coordination |
On the framing plan
Either way, the plan still communicates the universals of any framing plan: member direction and spacing, the bearing walls and beams, and openings. The difference is whether you are showing individual rafters with a ridge and hips, or a repeated run of trusses with a type callout.
A note on the tool
Both systems require project-appropriate design information. Framing Plan can help sketch the plan-view footprint, support assumptions, openings, and annotations. It does not calculate rafter members or connections, generate truss design drawings, or design temporary and permanent bracing.
Keep it preliminary
Use a preliminary plan to communicate the intended system and coordination constraints. The rafter scheme or truss package, building supports, loads, connections, restraint, bracing, erection information, and approvals must be completed by the responsible parties required for the project and for the code adopted in your jurisdiction, which places roof and ceiling framing in IRC Chapter 8.
Try it
For plan-view layout or a flat roof, open the framing studio, or read gable vs. hip roof framing next.