Question re: roof for workshop renovation

Normally I would ad the the roof after I have the siding on the gable end. I think most folks would just extend the gable style roof and not switch to a shed style roof.

-- W James Brokenbourgh Custom furniture maker http://artisticwoodstudio.com/

What you are doing is fine but and as a small addition like that 2×4s should be fine however…
1. You need more rafters, they should ideally be 16” on center, being a shed that may not require a permit or inspection allowing you to go less but you still should have one additional rafter in the center for support of the roof.
2. Because it is under an overhang it ties in nicely just make sure you put flashing all the way across and that it is properly laid in under the siding/boards but above the shingles. Flashing cement is what you want to use, don’t use caulk.
3. Make sure the beam above the door and that the rafters are tying into have been reinforced to support the extra load.

edit: A1Jim- put in the starter strip of siding, the narrow piece that will create the slope in the first full sized board, tack your flashing to that strip then put up the rest of the siding, that keeps the water from coming down the wall and under the roof.

-- --Rev. Russ in NY-- A posse ad esse