The other issue is the building code.
How far apart do you put boards for porch roof.
Just a saw kerf will do though i prefer a smoother less stress concentrating broad dish shaped router cut but with a 1 8 or so cut into the wood that additionally reduces the wood strength and screw holding power of nominal 1 think 3 4 actual wood.
The best size board to use is 1x4 pieces that are 10 feet long.
When you cut the rafters you ll need to make 3 separate cuts.
The smallest beams for patio covers are typically 4 by 6.
Too high a snow load means the purlins fail regardless of how close together you put them because a 2 4 or 2 6 flat can only span a certain distance between trusses as snow loads increase.
While your beam size ultimately depends on design factors such as whether you include a covered roof structure or open lattice strips a familiarity with conventional beam spans gives you an idea of how far apart you can space your posts.
This translates to seven rows of strips 20 feet long spaced two feet apart or 140 lineal feet of.
Before you cut your boards you ll need to measure the width of your building and calculate the exact length of each rafter.
If so you may want to go to 2 x 8.
However you will want to have boards that can be used as braces for the tresses.
That s a long span.
The higher the snow load the closer the purlin spacing required.
If you go that length you must block it every four feet which you need to do anyway for nailing the plywood.
The ridge cut also called the plumb cut at the top of the rafter the birdsmouth cut which itself comprises 2 different cuts where the rafter meets the building s wall and the tail cut at the base.
Another thing you will need to do is brace the second gable end on the roof and secure it.
You do not have to brace all the trusses just plumb the second gable.
In this example the section of roof is 20 feet wide and 14 feet from the fascia to the peak.