Roof Joist Vs Roof Rafter

Floor joist span use this table to determine the maximum lengths of floor joists based on species of lumber joist spacing and joist size.

Roof joist vs roof rafter.

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. 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. 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.

In a typical roof framed with dimension lumber the rafters rest on the exterior wall top plate at the lower end and bear against a ridge board at the top. For roofs that will experience heavy snow or wind and will span the same distance use 2 6 rafters. Rafter boards are fastened to the ridge board at the peak and the top plate where they join the wall. In finished space insulation is placed between the rafter boards and drywall or other material is fastened to the face.

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. If you have a simple gable shed roof then using 2 4 rafters makes more sense unless you have a very large shed. However in canada the most common material used in residential framing is wood so that is the material we will discuss here. Rafters are the building components that run diagonally from the wall plate to the apex of a roof structure.

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