Addition questions

[quickboat]

Hey Gents, been lurking about for years reading the garage experience here. Very interesting. I am now embarking on a detached garage expansion and need some help/advise and thought I would join. This is my existing garage and I am proposing a punched out and up addition and need some help on joining the two. I have fairly sharp elevation increase about 25 feet behind existing structure and at first was contemplating an all new building but drainage would force a drainage pipe through the structure and tree roots kind of make running electric a bear.
I wish to put 10' walls on the addition and go 4 foot wider. So the gable will step up half way back. I want to have the adjoining walls open between the two and don't know how to draw it up for permits. Both are stud wall and raftered. Can anyone direct me to the info I need? Will I need a header? Will rafter ties be enough?
Original structure: 20x24
addition: 24x22
ps The county (Hamilton) said I did not needed "stamped" drawings, but drawings that show construction enough to meet permit requirements: (http://building.hamiltoncountyohio.gov/sites/default/files/Accessory-05.pdf)

 

[oldironfarmer]

You likely don't have a truss at the back, just vertical boards for nailers. A truss added to the back side of that truss will support the existing roof. Then you can tear out the rear wall. End trusses only have to support half the load of intermediate of trusses if they are all on the same spacing. So an identical end truss needs no header under it. It will need some boards to nail the siding to.

The wider building (consider them separate buildings) behind will need an end truss to span the opening in that building.

Have you checked with your local authority to determine whether you have to have architect stamped drawings? If you do, you may as well get started with an architect up front so he can adequately advise you and avoid resubmittals in the unlikely event you don't get everything just right first time.

Looks like a great project!