Roof Joists Vs Rafters

Rafters form the foundation for attachment of the roof boards onto which the final roof covering is fixed.

Roof joists vs rafters.

The rafters carry the dead load of the sheathing and roofing material and the live loads above. In traditional timber they are 2 inches wide and 8 to 10 inches deep. 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. Roof rafters are typically joined where the two slopes converge along the ridge of your roof running all the way down to the eaves.

However in canada the most common material used in residential framing is wood so that is the material we will discuss here. Trusses and rafters have many common parts including the sloping rafter boards and a bottom joists that form the ceiling of the space below. 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. The rafters support the sheathing and typically run from the roof peak down to the eaves.

Rafters are the building components that run diagonally from the wall plate to the apex of a roof structure. Rafters are the building components that run diagonally from the wall plate to the apex of a roof structure. 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 may also carry the ceiling loads below on cathedral ceilings.

Rafters are typically 2 by 4 s 2 by 6 s 2 by 8 s or 2 by 10s. The major functional difference between the two is that trusses are built mostly with 2x4s in place of the wider dimensional boards. In traditional timber they are nominally 2 inches thick and typically 8 to 10 inches wide.