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.

In traditional timber they are nominally 2 inches thick and typically 8 to 10 inches wide. 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. However in canada the most common material used in residential framing is wood so that is the material we will discuss here. 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.

Rafter boards are fastened to the ridge board at the peak and the top plate where they join the wall. For roofs that won t experience heavy snow loads a gable roof can span up to 22 with 2 4 rafters. Rafters are the building components that run diagonally from the wall plate to the apex of a roof structure. 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.

For roofs that will experience heavy snow or wind and will span the same distance use 2 6 rafters. In finished space insulation is placed between the rafter boards and drywall or other material is fastened to the face. Rafters form the foundation for attachment of the roof boards onto which the final roof covering is fixed. If you have a simple gable shed roof then using 2 4 rafters makes more sense unless you have a very large shed.

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. The boards creating the slope of the roof are wider than lumber used to build trusses 2x8s 2x10s and 2x12s are most common in rafters vs. Conventional framing the first thing to understand is how a roof framed with wood i joists differs structurally from a traditional stick framed roof.