More accurately, I raised a portion of the house about 1/2", but nevertheless, part of the house is now higher than it once was. Here's how:
Soon after demolition was finished, we found the middle wall on the ground floor to be a bit wimpier than it should be. This wall supports half of the entire floor above, and is quite important. It sat on a very thin bit of concrete, instead of a proper footing with rebar. Instead of re-doing the entire wall and foundation, we decided to put in beefier posts at 6' intervals to hold up the floor above.
First, we had to jackhammer the existing deficient concrete, and dig a hole 2 feet square and 18 inches deep. There were 3 such holes. Here is a picture of one of them:
After putting in metal reinforcing bar into the hole, we mixed and poured concrete. The concrete was smoothed out to be flush with the rest of the floor, and a metal post base was partially embedded into the wet concrete.
Next, the hard part. I took my trusty laser level, and shot a perfectly horizontal line across the bottom of the beam these posts were to support. I found the beam to be quite wavy, with a significant dip of about 1/2" in the center. One end of the beam was also lower than the other. I realized that I couldn't raise either end of the beam, but I it did seem possible to raise the middle. Making possibilities reality is not so easy. With a sledgehammer, extra 2x4's, leverage, and the laws of physics, I raised our house.
I first measured the space between the ground and the beam. Then I cut some wood to be slightly taller than that space. I wedged the wood between the ground and beam at an angle, and sledgehammered it until it was vertical. You can see it buckling slightly under the weight of the floor above here:
This was done twice for every post. One temporary piece was wedged to the left and another to the right of the new post location. But cutting these temporary pieces taller than the space, I slowly raised the beam back to horizontal.
Next I repeated the process with the actual permanent 4x4 post. It sits at the bottom in the 'post base' that was previously cast into the concrete. A 'post cap' at the top connects it to the existing beam.
Many hours and much noisy sledgehammering later, the post is finally installed in it's correct location, and the beam is level:
I knocked out the two temporary pieces. Here are two posts installed. I still have one more in the middle to complete.
When finished, the new concrete footings and posts will have sufficient bearing capacity to hold the furniture, walls, roof, and people on the floor above. The beam should stay level and the concrete should not settle.