I could figure out how to attach a ledger board to the side of this wall through the studs on the inside, however I'm not sure how it would properly seal against the shed, if it should, if any flashing is required, etc. etc.

Anyone built something like this? Any considerations or things I'm missing to address?

 

I'd likely cut the existing roof back and set the lean to rafters on the shed wall. Support the other side of the lean to on posts with a beam header. Sheet the roof and shingle to match the shed. The facia will flow from the shed to the lean to, which will look like it was originally built this way. It'll also give a little more head room to pitch the lean to roof instead of starting under the soffit.

 

My lean too was built with the barn, metal roofing, but I'm in the same PA lines as you for depth and snow load. My posts are 44" deep, and my roof is a 4/12. It was attached with 2x12 where the external perlins (horizontal stringers, usually 2x4s) normally are on the pole barn. The lean to is "16x8" with a 1' overhang on the three edges. Headers are 2x12 and the roof stringers are 2x8s spaced 4'OC with 2x4s perlins at 2' spacing. Hurricane bracing is required.

Photos:

 

Since the shed is floating on a gravel pad I’d be inclined to use posts all the way around the lean-to and make it a freestanding structure not tied to the shed.

 

That’s what mine is…… 14 x20 free standing with metal roof. The high side against the existing garage is tucked underneath the eve of the garage roof. It stays dry but I do get leaves in. Mine is somewhat open…. The low side and back are just treated fence panels. The gate end is just 2 fence panels on hinders. Sorry no pictures. (In the winter I do add xtra support 2x6’s in strategic areas for the snow load).

 

The only discrepancy I see in the drawing you plan on mimicking is the roof pitch, in the drawing is 11.8 degrees 2.4/12 pitch. The pitch you want is 18.5 degrees for a 4/12 which is going to reduce the low side (outside wall) considerably below the 8' shown in the drawing if you go out the 10' shown.

What @JLAlbert said might be a better option by setting the rafters on the existing sheds rafter header. This will get your starting point higher thus accommodating the steeper 4/12 pitch which will give you a higher outside wall.

Figure out what your outside wall is by running an 18.5 degree line over 10' at a 10' starting height.

 

I'm following this thread as I also need to add an additional lean-to off the back of my small pole barn to house the 80 gallon air compressor, Sand Blaster with vacuum system and powder coating oven. They take up space that are used not so often and can be quite noisy inside the barn main area.
Plan to make it 16'L x 8'W x ??H and fully enclosed with sound proofing foam panels on the interior walls so we don't hear any unwanted noise.

 

You all make some great points that I should look more into. I would prefer not to build it free standing if avoidable -- digging down adjacent to the shed will be a PITA. I suppose a post outside of the existing pad would work, however that eats into the opening width by a several inches. The shed has had the chance to settle for 7-8 years...I was hoping to just attach it off the rear of that and keep it simple without any alterations to the shed. Hoping! LOL.

The 4:12 pitch was something that I read online, but, may not be required. Perhaps I could get away with less. I guess it depends what you read?

I'm happy to run whatever pitch/angle is appropriate, I'm not married to any. If I can use a 1:12 or 2:12, obviously that would be a lot more beneficial for losing less height.

 

The shed has had the chance to settle for 7-8 years...I was hoping to just attach it off the rear of that and keep it simple without any alterations to the shed. Hoping! LOL.

The shed will have settled but it will still move up and down and around a little bit as it floats on freezing/thawing/wet/dry ground. Posts set down below the frost line shouldn’t move, that’s why they need to be below frost line in the ground to keep them from heaving.

 

I pulled a permit for the original shed but didn't plan on pulling one for the lean-to on the back.

Neighbor is fine and he'd rather see the the tractor stored out of the way instead of between the driveway and his house.

You're right that there is some slope. I've been cutting and dumping a bit as I go around the shed to level things out in the yard. Eventual plan is a retaining wall. No issues cutting in/back/around anywhere. And I have plenty more dirt to pull from the front side to dump around the back as well.

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Ok, yeah you’ve been busy!!!

 

FYI, the 4:12 'suggestion' is for shingles. Less and there is a chance they will leak.
If you go less you would need rolled roofing or membrane.

 

Just a suggestion to think about while you are planning….

Think of building it wider than the minimum you think you need. I have an 8ft wide enclosed lean-to and if I manage to park dead center, I can just squeeze around both sides. Park off center and you can get along one side or the other, not both. It also makes it tough to use the walls for storage If you have it too small.

think of making the roof overhang longer, especially if you might enclose the wall. Figure a 18-20 in overhand from the outside of the posts will put the drip line right in line w/ walking along that wall. If you can make the overhang longer, you get a little more storage space along the wall, or you get a space to step out of the rain.

 

Beautiful grass!