Roof Joist Vs Roof Rafter

In traditional timber they are nominally 2 inches thick and typically 8 to 10 inches wide.

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 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. For roofs that won t experience heavy snow loads a gable roof can span up to 22 with 2 4 rafters.

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. 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. However in canada the most common material used in residential framing is wood so that is the material we will discuss here.

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. Rafter boards are fastened to the ridge board at the peak and the top plate where they join the wall. Rafters are the building components that run diagonally from the wall plate to the apex of a roof structure. As nouns the difference between joist and rafter is that joist is a piece of timber laid horizontally or nearly so to which the planks of the floor or the laths or furring strips of a ceiling are nailed while rafter is one of a series of sloped beams that extend from the ridge or hip to the downslope perimeter or eave designed to support the roof deck and its associated loads or rafter.

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. In finished space insulation is placed between the rafter boards and drywall or other material is fastened to the face. 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.