Some places have specific requirements to meet fire code when filling that space. For example, where I live you can't just place insulation bats between the studs because the narrow gap that would be left between the bats behind each stud is considered an airspace that could allow a fire to transit to the floor above. I do live in fire country and using bats doesn't look practical in your situation, this is just an example. I would just double-check the fire code to make sure that exactly how you are going to do it won't run afoul of that.

One big downside is your framing isn't correct. You should have fire blocking all around the top plates. And also at intervals along the wall length.

You would think that it would be a plumbing code requirement...and yet, here we are

I have had my basement dug out below me in a two story house while living in it with my wife and young kids.

So it is totally doable.

Step one is to spend a couple grand on a structural engineer. They will go from your attic down to see whats up and make sure whatever is done is safe.

Basin or sink wrench for the two grey plastic nuts, and likely a deep well socket with long extension and ratchet for the metal nut.

I was thinking something similar to Rafi89's reply just a bit ago:
If you can get to the plumbing from the other side of the wall, it could be what you need to do. Go to Youtube and look up Vancouver Carpenter on how to cut, and then patch a hole in drywall. He's got lots of great drywall vids. Once you've learned a little about how to do it RIGHT, it isn't so hard. But it's easy to do bad drywall jobs. I was doing bad ones for years until I found his vids.

Maybe you DON'T have to do this, and you can find cartridges that will replace what you've got. If you don't see the right thing at Home Depot or Lowes, find a plumbing supply, and pay a little premium for the free advice they've given to help you find - or not find a replacement.

However, I also do NOT like the looks of that grout. I suspect if you took some of that tile off you'd find black mold from moisture underneath. If you started taking tile off, you'd quite possibly end up putting up complete new concrete board to replace the sheetrock and doing new tiling. I wish you luck, and hope that regrouting does what you need!

it sounds like the check valve is bad, stuck in the open position. The check value is usually screwed into the tank, it may look like a brass adapter fitting. The small ones are not that expensive or hard to replace.

Gas should be 18" (likely 12" to 15" if I was a betting man) down. If you hand dig it gently with a shovel you should be fine. It takes a pretty good gouge to damage underground.

Further points against him doing any modifications.

Read around this thread. Dude is Renting.

In our case, it's when the bank says that for them to approve our mortgage application we either have to fix or get rid of the shed on the property we were buying and it was going to cost 3x the cost of removing it to fix it up

Don't know if they're called the same in the States but a set of monobloc tap spanners will do the job.

Good lord, this is insane. That texture could have been scraped or the drywall replaced, but not whatever this monstrosity is. Ask for money back, if they refuse, take them to small claims because no matter what they need to not do any additional work as they are totally clueless.

I wish you were my neighbor and/or dad.

Termites are only a problem in a few areas in Ontario (Canada) and, thankfully, I don't live in one of those areas.

My house is basically sitting on granite. The builder had to blast to dig the foundation. The foundation walls are waterproofed, and the floor is required by building code to be damp-proofed at minimum, so the basement should be pretty dry.

Mine was like this. Made extension to house. Dug out footings and left old dirt.

Hook a chain to it, and to the bumper of your truck. Floor it. Easy Peezy

RIGHT! I threw out an audible WTF when i opened the pictures

I think the big question isn't answerable from the picture and that's whether the frame and foundation is still good. OP when you get there take your pocketknife or a screwdriver and go around the inside of the base of the shed and kind of poke at things every few inches. If it's solid then that's good.. if you can poke into it easily that's bad. If it's just soft in a couple of places you can often fix that by bracing up that side and cutting out the rotten bits and sliding in new pressure treated. OTOH if it's rotten all around most of the base it starts getting a lot easier to just tear down and rebuild. You can also do the same poke-for-rot around the accessible bits of the outside.

There is a similar concern if the roof has been leaking that some of the roofing timber or sheathing might be rotten but that lands more firmly in the fix territory IMHO.

If I had to bed.. I'd bet on fix in this case. Although there's some clear rot on the threshold which makes me wonder a bit. And I'm mildly concerned about the sill plate on the uphill side where all the trash is.

It looks like there's a concrete foundation. You might do well to pull back some of the trash (those pipes and shit are collecting leaves and holding moisture there) and maybe a touch of the dirt from the uphill side of the shed to make sure water is draining around it and not into it. You basically want to make sure the bottom of the wood is not touching anything except the concrete. No leaves, no dirt, no trash.. and there's a couple inches of drainage below the wood as well.

I don't think I'd get overly fancy with the door, it's been patched at least twice.. pull that off and put some 1/2" treated plywood on it and good to go. That's assuming it's not in worse shape than I can tell which.. is about 50/50 odds from here hah. If you do need a new door if there's a local rebuildit or habitat for humanity or similar store around you that's a good place to get them for not to much.

Be somewhat careful with the tin overlay someone was suggesting. The idea with outside covering is you want the water to always have drip out. So you basically want all layers to look like

inside \\\\ outside

so they drain to the outside and there's no place to trap water. Simply slapping a sheet of tin around the bottom is a place to trap moisture behind and will likely cause the wood behind it to rot faster. If you cut the siding back and slid the tin up under it that could work.. but I doubt it's worth the effort.

If any of those limbs look like they can smack the roof/side of the shed in a breeze trim them back so they can't.

Use a push broom to gently pull the needles back off of the roof. If the roof it leaking but not to badly you can patch it with some roofing tar. If the decking (plywood under the shingles) is rotted out you'd have to replace the roof. If the rafters are rotten you can cut new ones to match and "sister" them alongside the existing when the roof decking is off. Putting on a new rood isn't terribly hard.. but would take a newbie soloing probably a couple days just to figure it all out.

You might have to replace some/part/all of the door frame. Looks like it's probably just 1x4's. If so you'll see how they're nailed on when you pull them off.. do the same. Back prime and paint the wall and the back sides of the replacement boards before you put the new ones up. If they ain't rotten don't replace them.. but they look kinda rotten.. You can also use some 1x4's or 1x3's to replace trim the corners that should cover that gap in the upper left side as well :) They're basically just nail one flush to the building corner and then nail the other one to it overlapping and also to the wall. Pay attention to how the ones are on there now and you'll figure it out.

You'll minimally want a hand saw, a claw hammer, a cats paw tool, a flat pry bar, a framing square (speed square is nice but not strictly necessary but for $10 extra...), a level, some 10 penny galvanized nails, and some 2" galvanized box might be useful for the edges of the trim, if you get into the door you'll also need a screw driver for the hinges (drill/driver would be my recommendation) and some shims for resetting the door frame. If you have to do the roof add a circular saw for cutting the plywood roof decking to size, a chalk line for marking the plywood and the roof tile lines, a roofing stapler for laying the felt, some roofing nails, enough felt to cover, drip edge, replacement wood where needed, box of roofing nails, probably 2 maybe 2.5-3 squares of shingles and a stack each of starter and ridge shingles.

The pictures look like shit, but it looks like they attached small blocks of 2x4 to the ceiling (hopefully to the joists, but who tf knows), and then either screwed nailed or glued the drywall to the small blocks. Why tf you wouldn’t just use a furring strip, idk

You can kill roof moss with laundry detergent.

This is the way. I also tip it when releasing the air.

Where I live we'd be wary of creating a protected path for termites, but sounds like not a threat to you. Any moisture wicking from below? If no moisture issues it sounds like a great opportunity for increasing that R value

Try making your “divot board” larger. It’s going flying because you are hitting a small surface area. Attach it to a larger piece of surface area and you’ll likely need not adhesion at all. Ideally, you could purchase a piece of green turf from Home Depot or Lowe’s, cut a 2’x2’ area and attach your “divot board” to that swath.

He joking

Plaster efflorescence. It's what happens when the calcium carbonate in the finish coat gets wet. Not a DIY job. You need a plasterer to repair that.