As an Amazon Associate I earn from qualifying purchases.
A rafter is a single sloping member cut on site with ceiling joists and collar ties added separately; a truss is an engineered triangulated assembly built in a factory and lifted into place as one unit. Trusses routinely span 30 to 40 feet or more with no interior bearing wall, use smaller lumber because the webs share load, and go up in a fraction of the time, which is why most new houses use them. Stick framing wins on additions, dormers, tight sites where a crane cannot reach, and irregular roofs where design changes happen as work proceeds. The decision people regret most is attic space: standard trusses fill the attic with webs that must never be cut, notched or drilled without an engineered repair detail, so if there is any chance of a future bonus room you must specify attic or scissor trusses before fabrication. This guide compares both on cost, span, labour, ventilation and the rules that are not negotiable.
Trusses arrive as engineered assemblies and go up fast. Rafters are cut and framed on site and leave the space open. The choice is mostly about what you want in the roof space and how complex the roof is.
| Roof trusses | Stick-framed rafters | |
|---|---|---|
| Where made | Engineered off site | Cut on site |
| Erection speed | Fast — a roof in a day | Slower |
| Labour cost | Lower | Higher |
| Clear span | Longer, without interior bearing | Usually needs a ridge beam or bearing wall |
| Attic space | Filled with webbing | Open and usable |
| Site changes | None — never cut or notch a truss | Adaptable |
| Complex shapes | Priced heavily by the plant | Often easier |
| Lead time | Weeks | Material is off the shelf |
| Building width | 4/12 rafter | 6/12 rafter | 8/12 rafter | 6/12 ridge height |
|---|---|---|---|---|
| 24 ft | 12.6 ft | 13.4 ft | 14.4 ft | 6 ft |
| 28 ft | 14.8 ft | 15.7 ft | 16.8 ft | 7 ft |
| 32 ft | 16.9 ft | 17.9 ft | 19.2 ft | 8 ft |
| 36 ft | 19 ft | 20.1 ft | 21.6 ft | 9 ft |
| 40 ft | 21.1 ft | 22.4 ft | 24 ft | 10 ft |
Never cut, notch or drill a truss. It is an engineered assembly and any modification voids its design — even drilling a chord to run a cable needs sign-off from the truss designer. If you want storage or a future room, that has to be specified at the design stage as an attic truss, which is a different and more expensive product.
Each of these covers one configuration: what distinguishes it, the spans it is used at, and the constraint that decides whether it will work on your building.
Attic truss · Scissor truss · Mono truss · Raised tie truss · King post truss · Queen post truss · Gambrel / barn roof
Usually, in labour. They arrive engineered, go up fast and span further without interior bearing walls. What they cost you is the attic space, which is filled with webbing.
Never. A truss is an engineered assembly and any cut, notch or drilled hole voids its design — even a chord drilled for a cable run needs sign-off from the truss designer.
Not safely on standard trusses. The bottom chord is designed for the ceiling and its own weight, not storage loads. Attic trusses are a different, more expensive product specified at design stage.
On a retrofit or addition, on an awkward shape a truss plant would price heavily, and any time you want the roof space usable now or later.