It depends on the size of the deck you're looking to do, the joist span and the beam size will dictate the number of posts needed to support the structure.

The house area is 24 wide and deck would be 12.5 depth .
Here’s a drawing.
if posts are 4 feet in from each side the 29 foot deck span it would be 12 feet between posts.

You cant cantilever the girder 4'. I believe the chart shows that you can only go 2'

You also can't attach deck ledger to the cantilever on the house. You will have to run a beam from the main house to the girder. and attach another beam to existing deck which is over the addition. Something like this

Depending on the beam you select, you will have to calculate the tributary load on the beam and go by that so most likely you will end up with 3 columns for 29' span.

Hey, thanks. Going to frame around the cantilever.
Went with wife stairs, framed 5 foot wide and wondering if too wide and should take out a stronger.

I ended up taking out a stringer and added a joists up top so went from 60 inches to 48 wide.
I thought when building would drop the stairs but since only doing a corner posts there would not be two posts to attach a dropped header. I cut back the island and reattached the stringers .

I will be adding a mid support 6 feet up with posts and footings attached to stairs

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Do you have a picture on how i can secure a dropped header without any support posts to attach to? Would be interested in dropping it to reduce the number of stairs

Nevermind my comments above, I cut back the island platform so if I did a drop header now I would not have the platform be 36 inches to code. Looks like I am committed to this setup now.
Thanks for the replies

No, you don't have to cut the platform back and there is no need for drop header. I have to run out again, when I get home I'll do a sketch for you. It's very simple and it takes 10-15 minutes to add support for the stringers.

Brian, here is one way of doing it.

Thanks. I meant I already cut back my joists With the stringer level with my Island I am just 36 inches at code. If I drop now my island loses 11 inches and will not be to code.