Rafter Vs Joist Flat Roof

Joist is a term used in construction for load bearing planks that run horizontally or nearly to horizontally to ground.

Rafter vs joist flat roof.

They can be concealed or exposed and there will be more joists than beams. In traditional timber they are nominally 2 inches thick and typically 8 to 10 inches wide. If you have a low sloped roof or flat roof of less than 2 in 12 these evenly spaced planks will be called roofing joists. 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. Trusses and rafters have many common parts including the sloping rafter boards and a bottom joists that form the ceiling of the space below. These triangulated structures with a high degree of strength and stability due to the geometry used form both the joist and rafter components of a building. A roofing joist is a horizontal member that runs across an open space.

In many modern construction projects prefabricated roof trusses are used. Roof joists generally join opposing walls and support the ceiling below and or the floor above.