Roof Truss vs Rafter: Which Should You Use?
Trusses cost less and install faster because they are factory-built and need no interior support wall; rafters cost more and take longer but allow a fully open attic and custom rooflines. Most new residential construction uses trusses — rafters are chosen when attic space or an unusual roofline matters more than speed and price.
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Truss vs Rafter, Side by Side
| Factor | Truss | Rafter |
|---|---|---|
| Cost | Lower — factory-optimized material use | Higher — more labor, more lumber |
| Install speed | Fast — pre-built, craned into place | Slower — cut and assembled on site |
| Attic space | Reduced by web members (unless attic truss) | Fully open, usable attic |
| Interior walls | No interior load-bearing wall needed | May need interior support for long spans |
| Design flexibility | Fixed by engineered design | High — custom rooflines, vaulted ceilings |
| Modification after install | Cannot be cut or altered | Easier to modify later |
Trusses became the dominant residential roof framing method through the mid-to-late 20th century as pre-engineered wood trusses with punched metal connector plates made factory production practical — a truss uses roughly 20-30% less lumber than an equivalent rafter roof because engineered triangulation puts every member into pure tension or compression instead of bending, which is a far more efficient use of material. This is also why trusses install faster: an entire truss arrives ready to lift into place, while a rafter roof is framed piece by piece on site.
Rafters remain the right choice when the ceiling needs to follow a custom shape a stock truss can't (cathedral ceilings, dormers, irregular rooflines) or when the attic itself needs to be fully open and usable without ordering a specialty attic truss. For a standard rectangular roof with no unusual interior requirements, a truss is almost always the faster, cheaper option.
- Top chord — the sloped outer member that carries roof load down to each joint; two top chords meet at the ridge.
- Bottom chord — the lower member spanning wall to wall, resisting the outward thrust from the top chords and often doubling as the ceiling joist.
- Web member — the internal diagonal and vertical pieces that triangulate the truss and transfer load between chords, either in tension or compression.
- Gusset plate — the connector (a punched metal plate in wood trusses, or a bolted/welded plate in steel trusses) that joins members at each panel point and transfers force between them.
- Span — the wall-to-wall horizontal distance the truss covers.
- Rise — the vertical distance from the wall plate to the ridge, set by span and pitch.
Frequently Asked Questions
Is it cheaper to use trusses or rafters?
Trusses are generally cheaper — they use less lumber overall due to efficient triangulated engineering, and their fast factory-to-site installation reduces labor cost compared to framing rafters piece by piece on site.
Do trusses or rafters give more attic space?
Rafters give more usable attic space, since there is no bottom chord or web members filling the interior. Trusses can also achieve a usable attic space with a dedicated attic (room-in-roof) truss, at a higher cost than a standard truss.
Can you convert a truss roof to rafters, or vice versa?
Converting truss framing to rafters (or the reverse) after construction is a major structural change requiring a full engineering redesign — it is rarely cost-effective compared to designing for the right choice from the start.