How Far Apart Do You Put Boards For Porch Roof

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. That s a long span. 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. 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.
This translates to seven rows of strips 20 feet long spaced two feet apart or 140 lineal feet of. You do not have to brace all the trusses just plumb the second gable. The best size board to use is 1x4 pieces that are 10 feet long. If so you may want to go to 2 x 8.
Before you cut your boards you ll need to measure the width of your building and calculate the exact length of each rafter. If not the patio roof only bears it s own weight and the block stiffens the joists dramatically. However you will want to have boards that can be used as braces for the tresses. Another thing you will need to do is brace the second gable end on the roof and secure it.
The common 4 on center design is suitable for snow loads up to 60 for most applications. Do you get a massive amount of snow. The higher the snow load the closer the purlin spacing required. In this example the section of roof is 20 feet wide and 14 feet from the fascia to the peak.
If you go that length you must block it every four feet which you need to do anyway for nailing the plywood.