As I write this, I have a slight lean as I walk on my floor in some parts of my house, and it's even worse on the upper floor. In some parts upstairs, it feels almost like you have to grab something. Visitors don't notice this, but I do. The lean was noticed by my dad as well when he stayed with us, got up, walked in the dark across the floor upstairs, and ended up in my bedroom when he was expecting it to be the bathroom. He said, "Yeah, you're right. The floor leans up here."
About ten years ago, I built my 4500sq ft house and the scammers who built my foundation flew the coop and are no longer found. All was fine for the first couple months, but then a long ridge appeared down the middle of the house floor, lifting that small section up about a little under a quarter inch. So, I called the builder out to remove the ridge. He brought his jacking equipment and was doing great in removing the ridge until we got to the kitchen, which was the remaining part. When we got there, it was pretty finicky and didn't want to go down. He called out his assistant and I heard a sledgehammering going on. Then, the whole house shook like an earthquake, an entire wall sunk down about 2 inches, and huge cracks appeared in several parts of the house. As well, the back of the house seemed to have gone down about 1.5 inches.
In this emergency, I fired the builder and told him never to come back. I then called out RamJack. They gave me an estimate on the entire thing for $17,000 USD and brought out stainless steel piers. They are stainless in that they rust on the outside patina -- so, the cheap stainless, they told me.
What they found when they inspected was that my foundation was done by fly-by-night scammers who basically only gave the impression of a foundation. It was pretty good in some parts, but in other parts they failed to use rebar, pour concrete, and only had the sunk-in part of the foundation going down about 2 feet, rather than 3 or more feet. A couple columns were only about 1.5 feet down into the earth!
Meanwhile, RamJack also discovered that my water table was high, and recommended that I get a drainage expert involved. They said they could dig down about 3 feet and hit water. (Later, a Charleston architect engineer visited my house and said that high water tables were common and that he had seen worse. He said that I should work towards improving drainage, but that for the most part the house will be okay because I had so many piers (about 36 of them) and several of the key ones were RamJack steel piers.)
Anyway, they managed to repair much of the house and I thought all was great. But then they got to the back of the house, and said they under-estimated and needed to request another $20,000 USD to finish! So, I fired them too. They only got $17,000 USD out of me.
So now all is well except that I need to bring up the entire back wall of my house, which is about 50ft long, up about 1.5 inches. I used a laser measure to figure this out from multiple locations, following the instructions on the box. More than 4 years has passed since the RamJack guys were here, and the house has stayed steady with no more sinking.
TL;DR: Therefore, what's the proper way that a contractor needs to raise the 50ft back wall of my 4500sq ft house about 1.5 inches, as affordable as possible? I mean, as I interview contractors, I want to see how close they will be to your assessment.