Roof Joists Vs Rafters

Trusses are of many types.

Roof joists vs rafters.

Collar ties placed horizontally halfway down the rafters hold the rafters and roof planes together. Rafters are the building components that run diagonally from the wall plate to the apex of a roof structure. Trusses only use 2 4 lumber and are constructed using a web of 2x4s for strength. There is no need for bearing posts under the ridge board which is nonstructural.

The main difference between joist and rafter is that the joist is a horizontal structural element transferring load from flooring to beams typically running perpendicular to beams and rafter is a structural members in architecture. In traditional timber they are nominally 2 inches thick and typically 8 to 10 inches wide. Rafters form the foundation for attachment of the roof boards onto which the final roof covering is fixed. They are secured at the bottom by ceiling joists.

The reason for this is that flat or shallow roofs withstand much more abuse and loads than steeper roofs making wider shed roof rafters a necessity. Continuous ceiling joists or collar ties span from rafter to rafter. However in canada the most common material used in residential framing is wood so that is the material we will discuss here. Lastly remember that we are not talking about trusses in this article just rafters.

The major functional difference between the two is that trusses are built mostly with 2x4s in place of the wider dimensional boards. The joist also called bandsill supports the load which the floor is built to bear it is like the skeleton a building. A rafter is a traditional roof framing method in the form of elongated lumber that s normally inclined from a central ridge beam and joins with the outer walls. Throw in the element of a construction budget and this is where rubber meets the road.

Stick framing is flexible and may. This structural support comes in the form of roofing joists ceiling joists rafters or trusses and can be made from a variety of materials including wood metal reinforced concrete etc. Constructing a roof using rafters is also known as stick framing which simply means that each rafter is built on site with lumber every piece of lumber is carefully measured cut and tightened together labor. The simplest is a planar truss which is used as a roof support system.

Trusses and rafters have many common parts including the sloping rafter boards and a bottom joists that form the ceiling of the space below. While rafters are less and less frequently used today due to the higher cost of rafters vs trusses they do have certain advantages. Joists are used in floors and as column support.