Trusses, Rafters... What the Heck is the Difference?
One of the frequent questions I am asked is: what is the difference between trusses and rafters?
Rafters are sloped framing members running downard from the peak of the roof all the way to the plates of the outside walls. They are the support for the roof load. Ceiling joists tie the outside walls together, support the ceiling materials for the room below, and secure the bottom ends of the rafters.
Carpenters build conventional rafter roof frames on-site. The rafters are installed one piece at a time.
Roof trusses are engineered and pre-fabricated, triangulated wood structures which are built in a factory. They are designed to carry the load of a home’s roof to the outside walls, shipped to the construction site, and installed using a crane after the home’s walls have been framed.
The triangles formed by the beams, bars and ties allow the truss to distribute the weight it carries over a broader area.
Trusses come in many varieties. Two are shown below.
According to the National Association of Home Builders (NAHB), conventional roof rafters and ceiling joists are less often used in new home construction these days. In fact, in 2008, about 4 out of 5 homes nationwide were being built with pre-manufactured roof trusses instead of traditional rafters.