The structure of a roof can include rafters, trusses or a combination of the two. Both trusses and rafters have a triangular shape, but trusses have a web of supporting triangles inside the main frame to provide extra support. Rafters contain sloping outer beams that provide support.
Both trusses and rafters are assembled before they are added to the roof structure of the home. Roof trusses are assembled in a factory with pre-engineered joints and structures. Roof rafters are assembled at the construction site.
Roof trusses can save time by coming pre-assembled. Although they can initially cost more than rafters to purchase, they can cut labor costs for roof construction significantly. Roof rafters cost less than trusses to purchase and can be customized at the construction site for the house's specifications.
The overall structure of roof rafters is a large triangle shape containing two primary outer beams that provide much of the support for the roof. The structure of roof trusses contains multiple beams that provide the same overall shape but with a series of triangles inside that help to distribute the weight load of the roof. The two basic types of trusses are the scissor truss and the cambered truss.