[3onthetree]

to explain, there will be . . .

How bout that sketch and a few basic dimensions? A blind man's chicken scratch is fully accepted here, so don't hold back. Or at least some pics and we can visualize the word salad.

 

[3onthetree]

I think . . . maybe . . . I understand what you want. If you make the fascias even on the gable vs. sheds, then there will be no complicated overhang connections.

The main open gable's structure is minimized over the existing roof, there it would be more like a dormer, but the existing roof framing should definitely be looked at. The larger design points would be that it could require some hefty framing members to support an open cathedral. Those can be reduced if you don't mind some framing ties within the open ceiling space (i.e. rafter ties and collar beams).

If the shed ceilings are also exposed, you would have a funky situation where it connects to the gable framing. Not sure what the shed over the utility room door is accomplishing if you want one there.

Your deck, which I usually don't see framed like that anyway, does not look capable of supporting these roofs. You would have separate columns/footings.

 

[3onthetree]

After looking at your plan, if he built the sheds first he could put vally beams in that would avoid the sliding door.

I thought about valley beams to avoid seeing part of the gable ends if the shed roof is exposed underneath, but then those beams would have to be very substantial taking both shed and half the gable, and would end on top the existing roof. Whereas a level gable beam on each side would be simpler and could be supported by the wall.

He does need to figure his roof slope so he can determine how wide this gable is, then slide it back and forth so the loads avoid those openings, your instinct that the headers wouldn't be sufficient is probably right on.

 

[3onthetree]

You could do that, but it's pretty complicated so you'll have to figure out all the angles for the beams for him :wink2:

 

[3onthetree]

How do you plan on using the deck with the kitchen at the front of the house?
Decks, especially this large, should be layed out just like you lay out rooms in a house, with circulation onto the deck and off down the stairs. The differing roof shapes will seem like different "rooms." Under the gable is where everyone will want to be. Don't feel it necessary for the entire roof to be symmetrical, your house and functions are not.