Oh boy. I recently ventured down into the basement and noticed a gaping crack in the brick wall running down the center of the house. It has always had a settlement crack, but I don't ever remember being alarmed by it. This time I was, and (I think) rightfully so.
In construction lingo, it's what they call "not good." I know it's difficult to tell from a picture if you've never been in my basement, so I'll do my best to describe what is going on. Through the doorway and on the right half of the picture is a standard full-height basement with a concrete floor. On the left side of the picture is a crawlspace. It's just dirt held back by a short retaining wall that is two bricks thick. The knee wall is integrated into the full-height brick wall. The knee wall is bulging out a little bit around the doorway, and the brick above (that forms the left side of the doorway) is going with it, widening that settlement crack.
We met with one contractor today and will talk with two more before we make a decision on how to fix this. In the meantime, we've placed a jack under the door lintel to catch the weight in case the wall takes a dive.