In traditional timber they are nominally 2 inches thick and typically 8 to 10 inches wide.
Roof rafter and beams.
The table below shows built up beams for 31 3 psf of snow loading.
A rafter is one of a series of sloped structural members such as wooden beams that extend from the ridge or hip to the wall plate downslope perimeter or eave and that are designed to support the roof deck and its associated loads.
You will need a roof beam as a nailing surface to support the rafters.
Sample maximum roof beam span table feet inches.
Some of these can support the roof and prevent ridge sagging and wall spreading.
In home construction rafters are normally made of wood.
Typically the roof beam is made by nailing together a few pieces of dimensional lumber.
Collar ties rafter ties tension beams structural ridge beams.
Maximum rafter spans for a patio roof in areas with mild climates patio roofs are generally designed for loads of 30 psf pounds per square foot.
Rafters are the building components that run diagonally from the wall plate to the apex of a roof structure.
This article describes and illustrates the different types of support that prevents roof sagging and wall bulging at buildings including definitions of collar ties rafter ties and structural ridge beams.
Is that beam is any large piece of timber or iron long in proportion to its thickness and prepared for use 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 can be a raftsman.
Rafters form the foundation for attachment of the roof boards onto which the final roof covering is fixed.