You might contact Orenco Systems, inc... they're able to put in Alternative systems that are usually much, much lower on up-front costs than mound or sandfilter systems, and work better.
I built a structure 6ft from the centerline of the power line route, despite the power company telling me 15ft... because the easement they had recorded in 1936 said the easement was 5ft to each side of the centerline.
I planted crops up 6ft too, and got quite the settlement from the power...
A solid weld along the top and bottom is not necessary... you could easily do 3" welds, on 9" centers and get 99.9% of the strength.
I would also recommend making a box section instead of an I-beam, as I beams are a bit noodley to handle if you can't lift them from above, etc.
For the joints...
For your safety and that of your loved ones, get a better lid. fiberglass ones like this one made by Orenco are incredibly strong.
https://pacesupply.com/Product/osifl21g
in 2021, steel buildings and contractor labor were hard to find and $$$$$$$$$$$$
I looked at a post-frame, but I couldn't dig a hole more than 18" deep before hitting solid rock, so the depth wouldn't be enough, and the AHJ literally had plans read-to-use for the shop I wanted to build. I...
I built a lift for installing C5 Corvette transaxles more easily.... balances just a fuzz heavy on the front with the torque tube on. It minimizes how far I have to lift the car, and is a good place to store the trans while I finish building my Nova, which is on a C5 suspension.
I lived in Portland OR and had a neighbor who fed squirrels. A coffee can of peanuts off her back porch every evening. The squirrels proceeded to destroy all kinds of things on my property, and the feed attracted rats who got in my garage all the time.
I had another neighbor who was tired of...
I like to use a 200F rated flex hose from the compressor to the hard piping on the wall, then copper from there.
Pex-AL-PEx is another good system, like Rapid air.
Standard pex with metal fittings might work at pressures less than 150, but keep it 100% out of sunlight.
dont' use PVC. Some...
If the building walls are essentially aligned with the edge of the concrete, of within 1-2 inches, you could use a Z shaped flashing that overhangs the edge of the concrete a bit, and tucks under the edge of the metal siding. a sealant under this Z flashing would help prevent wicking. Sealant...
I just built a 30'x 48' building.
Build it 32' wide. You'll be ripping all of your sheet goods down... but for some reason it seems to always take more than half the sheet...
As for whether 25x30 is big enough - there's a simple formula for this.
X=N+250
Where:
X - Ideal shop size...