You will need a roof beam as a nailing surface to support the rafters.
Roof rafter and beams.
Typically the roof beam is made by nailing together a few pieces of dimensional lumber.
In home construction rafters are normally made of wood.
In traditional timber they are nominally 2 inches thick and typically 8 to 10 inches wide.
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.
Rafters are the building components that run diagonally from the wall plate to the apex of a roof structure.
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.
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.
An essential part of planning a patio roof or gazebo project is determining the number size and spacing of rafters beams and posts according to the loads they will carry.
Some of these can support the roof and prevent ridge sagging and wall spreading.
Once again you will need to look at your local charts and use your local snow load factor to determine the maximum span for a given wood rafter size.
Rafters form the foundation for attachment of the roof boards onto which the final roof covering is fixed.
Collar ties rafter ties tension beams structural ridge beams.
Sample maximum roof beam span table feet inches.