Rafter Vs Joist Flat Roof

In many modern construction projects prefabricated roof trusses are used.

Rafter vs joist flat roof.

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. Depending on the construction they may lie flat or be pitched. A roofing joist is a horizontal member that runs across an open space. Rafters form the foundation for attachment of the roof boards onto which the final roof covering is fixed.

In traditional timber they are nominally 2 inches thick and typically 8 to 10 inches wide. 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 are the building components that run diagonally from the wall plate to the apex of a roof structure. The major functional difference between the two is that trusses are built mostly with 2x4s in place of the wider dimensional boards.

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. They can be concealed or exposed and there will be more joists than beams.