We’re getting quotes for replacement outbuilding, and plan to include a 12ft overhang for implement storage very similar to what you describe. That’s how most “real farmers” around here do it. Much easier to hook up and put away the implements if they’re side by side and you just back the tractor up to each one.
For the tractor storage,
how about leave the end sidewall open (or have swinging doors), and then you can back in with the tractor+mower parallel to the shed? You’d have to be sure the roof is tall enough to accommodate your ROPS. (if it’s tight, you could just lower the grade in that section of the shed). But if you’re only allocating 20’ to all implement storage, the tractor+mower running lengthwise wouldn’t leave room for much else. But honestly, I’d really want a roof over both of those pieces of equipment. I’m assuming you’d pull in so the tractor’s the one that gets to enjoy the roof, but still, I’d be sad to see my rotary sitting out there exposed to the elements all the time.
One thing you’ll want is a level, firm surface under your implements. Trying to hook up a PTO shaft on uneven ground is a PITA. And lighting (solar light would be fine, it’s not like you’d have it on for hours).
On ours, I’m going to put up a curtain using shade screen, to help keep out driving rain or snow. And it’ll just look nicer than seeing a bunch of machinery lined up. But that’ll probably be a 2nd year kind of project, budget-wise.
