Roof Joist Vs Roof Rafter

Conventional framing the first thing to understand is how a roof framed with wood i joists differs structurally from a traditional stick framed roof.

Roof joist vs roof rafter.

Rise and run means that a 6 12 pitch roof has 6 of rise vertical for each foot of run horizontal. 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. If you live in an area that requires a shed roof rafter to support a heavy load then an spf rafter can only span 7. 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.

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. 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. As mentioned above a 2 4 spf shed roof rafter can span 11.

Collar ties placed horizontally halfway down the rafters hold the rafters and roof planes together. Rafter boards are fastened to the ridge board at the peak and the top plate where they join the wall. In traditional timber they are nominally 2 inches thick and typically 8 to 10 inches wide. 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.

Our roof rafter calculator tools are handy for calculating the number of rafters needed rafter length calculator lineal feet of rafter board feed in ridge and sub facia and the total board feet in the roof. 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. In finished space insulation is placed between the rafter boards and drywall or other material is fastened to the face. Rafters are made from sloped framing boards of dimensional lumber usually 2x8s or 2x10s connecting the roof peak called the ridge board to the plates of the exterior walls.

An syp rafter can span 11. They are secured at the bottom by ceiling joists. Rafters form the foundation for attachment of the roof boards onto which the final roof covering is fixed. Both of these are for light roof loads.