I'm reworking a shed to make a cold room for storing seedlings in spring. Part of this is wraping the building with strawbales. I want to increase the overhang to 3 feet beyond the bales.
For this purpose, I've sistered 2x6 to the existing trusses, going from the peak to 4 feet beyond the wall. These are not notched. Each 2x6 is secured with 12 #10 3 inch ceramic coated deck screws.
Purlins (steel roof) are 2x4's on edge, with blocking at the outer edge, and where they meet. I figure the blocking will keep the purlin from rolling. Purlins are secured with the same 3" screws at the bottom of a 2" hole. (So only 1.5" of the 2x4 is held by the screw.)
Slope of the roof is 18 degrees.
We get moderate snow. In 20 years the heaviest snow I've seen on the main house roof is 2 feet of light fluff -- equivalent to about 3 inches water, so about 15-20 lbs per square foot. Being a metal roof, snow tends to slide off of it readily.
Walking around on the frame that I've done so far doesn't feel bouncy.
I'm not worried about snow load, but the thought just occurred to me, that this is a lot of roof to catch the wind. The area is fairly sheltered. My wind chime nearby complains of boredom.
(We are in a rural county, and code does not apply to utility buildings. Recommended practices are fine.)