Roof Joists Vs Rafters

Rafters are the building components that run diagonally from the wall plate to the apex of a roof structure.

Roof joists vs rafters.

The major functional difference between the two is that trusses are built mostly with 2x4s in place of the wider dimensional boards. However in canada the most common material used in residential framing is wood so that is the material we will discuss here. The rafters carry the dead load of the sheathing and roofing material and the live loads above. 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.

In traditional timber they are 2 inches wide and 8 to 10 inches deep. Rafters form the foundation for attachment of the roof boards onto which the final roof covering is fixed. Rafters form the foundation for attachment of the roof boards onto which the final roof covering is fixed. Trusses and rafters have many common parts including the sloping rafter boards and a bottom joists that form the ceiling of the space below.

A joist is a horizontal structural member used in framing to span an open space often between beams that subsequently transfer loads to vertical members. Rafters are the building components that run diagonally from the wall plate to the apex of a roof structure. Rafters may also carry the ceiling loads below on cathedral ceilings. The rafters support the sheathing and typically run from the roof peak down to the eaves.

Roof rafters are typically joined where the two slopes converge along the ridge of your roof running all the way down to the eaves. 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. However since steeply sloped roofs of more than 2 in 12 are raised up too high for the parallel planks to be considered joists they go by a different name and are instead called rafters.