need to know size of steel i beam for a 20 foot span. i am building a lean to in backyard the size is 10by 20 .it will be 8 feet height on one side and 7 feet on the other
The beam supplier should have rating for this. But you need know load/wind load etc. I would look for plans and see what they say to use. Even if they say use wood you can figure out the load rating from that.
