I build a 16 foot by 30 foot lean to run in shed for my (2) shire horses. I would like to add a 4 foot overhang that would be shingled. I can’t attach new rafters to existing ones because there is a ledger board in front of them. For a 4 foot overhang, do you think I would need outside post to support this overhang? I have a picture of what I have done so far, I framed it but I feel is not enough support, it feels flimsy for Florida. The lean to post are 6x6 (4) foot in ground. 12 feet in front/10 feet in back. This is work in progress. What would be the proper way to frame this overhang?Thanks advance.[ATTACH=JSON]{“data-align”:“none”,“data-size”:“medium”,“data-tempid”:“temp_62859_1578676673666_247”}[/ATTACH]
I can’t open your picture, so I’ll assume you want the 4 ft overhang to essentially cantilever out from the existing roof, and you want it to run the length of the 30’ lean to? – thus making your existing 16’ ft roof into a 20’ roof?
If so, you could have attached the rafters (for the 4 ft. overhang) to the lean to ledger board with u-shaped joist hangers provided the ledger board is at least a 2x10. And the 4’ rafters obviously need something to sit on or attach to at the front…
…so 6x6 posts should be installed – one on each end and at least one in the center (of the 30’) to handle the weight of plywood and shingles and also withstand wind, and to allow for either a header/beam for the rafters to sit on, or a ledger board for the rafters to attach to with joist hangers.
30’ ft is too long a span to support even a 4’ roof without a center post (or more) and if you’re using conventional lumber the 15’ spans created by a single center post are very long as well, so you will have to either use 2x10’s doubled up or even 2x12’s which might not leave you with enough headroom given the pitch of your roof.
Of course you could always use LVL’s which would easily span 15’ ft without the need for more than a single center post. Just my opinon.
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Yes – your corners are unsupported which is why the overhang seems flimsy. But since your area does not have the worry of snow load, the overhang might stay up there just fine unless you get some serious wind.
Up to you of course – but posts should be in corners + only one in the center (to avoid ‘post clutter’) + a significantly sized header for your overhang joists to sit on. That being said, you would also have to fill or partially fill in the 4 ft space between the main shed and the corner post so a horse doesn’t try and squeeze through get injured etc.
If you want to leave your construction ‘as is’, then I would definitely remove the (single) angle supports you have now – the ones on the two center posts – and replace them with 2 angle supports per post = one on each side of the post. The side surfaces of the post will offer a much stronger attachment. Then you can nail a 6" block of wood on the inside face of the ledger board, right inbetween the two triangle supports – again this will offer you much better nailing surfaces and the construction won’t feel as flimsy.
As for the corner posts, you can add one more triangle support on the inside of each post. And once you add siding to fill in the 1/2 diamond shape created by shed roof + triangle support, your stability will also increase. Again, only my opinions! 
