Roof Joists Vs Rafters

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.

Roof joists vs rafters.

Rafters are the building components that run diagonally from the wall plate to the apex of a roof structure. 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. Rafters form the foundation for attachment of the roof boards onto which the final roof covering is fixed. 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.

The rafters support the sheathing and typically run from the roof peak down to the eaves. Rafters may also carry the ceiling loads below on cathedral ceilings. The rafters carry the dead load of the sheathing and roofing material and the live loads above. Rafters are the building components that run diagonally from the wall plate to the apex of a roof structure.

In traditional timber they are nominally 2 inches thick and typically 8 to 10 inches wide. Trusses and rafters have many common parts including the sloping rafter boards and a bottom joists that form the ceiling of the space below. In traditional timber they are 2 inches wide and 8 to 10 inches deep. 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. 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. A ceiling joist is simply a horizontal framing member that runs between walls or rafters to support a ceiling say editors while a rafter tie is a horizontal framing member that runs between rafters to resist the outward thrust of the rafters.