Roof Joist Vs Rafter

Rafter span tables use these tables to determine lengths sizes and spacing of rafters based on a variety of factors such as species load grade spacing and pitch.

Roof joist vs rafter.

Without the tie at the bottom the rafters must be supported at their upper end to prevent the rafter thrust at the lower end. 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 nominally 2 inches thick and typically 8 to 10 inches wide. Roof rafter span use this table to determine the maximum lengths of roof rafters based on species and grade of lumber spacing dimensions load and slope.

Conventional framing the first thing to understand is how a roof framed with wood i joists differs structurally from a traditional stick framed roof. Floor joist span use this table to determine the maximum lengths of floor joists based on species of lumber joist spacing and joist size. The major functional difference between the two is that trusses are built mostly with 2x4s in place of the wider dimensional boards. Both of these are for light roof loads.

Rafters are the building components that run diagonally from the wall plate to the apex of a roof structure. An syp rafter can span 11. The first case is when the ceiling joists are oriented perpendicular to the rafters. The load resisting concepts of the vaulted ceiling are completely different.

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 other common case is the cathedral or vaulted ceiling. Trusses and rafters have many common parts including the sloping rafter boards and a bottom joists that form the ceiling of the space below. 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. As mentioned above a 2 4 spf shed roof rafter can span 11. Visit the roof framing page for more information on cutting roof rafters and visit the roof pitch calculator for determining rafter lengths based on rise and run.