My old house, c1915, has concrete block foundation walls. Part of the basement has walls that go all the way down, about 7'. The other part the walls stop just below grade, thus part of the house only has a crawl space. My guess is that at some point someone came in and reclaimed part of the crawspace for living space and when they did they came in about 2', towards the inside of the house and built concrete block retaining walls that are about 4' tall. They then capped the area between these retaining walls and the exterior walls with concrete. I'm sure there is a term for this, but I can't think of it.
In any case, my chimney stack was built in the area that is/was crawl space, so when 1/2 of this area was reclaimed they also built a retaining wall around two sides of my this stack. The problem is that on one side, they didn't seem to finish it, so it appears someone just laid blocks vertically, one on top of the other, with no stagger to the joints. Obviously, this isn't very stronge, so I can see the beginnings of failure on those. Luckily, it's only two columns of block, so it shouldn't be too hard to repair and fix correctly; however, when I do this, I'd like to turn the corner into the area that has no retaining wall and is still dirt crawl space. The dirt ends about the height of these walls.
I just think turning this 90 and going a foot or two would add that much more strength to the entire setup. The dirt crawlspace has no wall in front of it, it's just kind of there in this section of the basement and the dirt starts on what would be the back side of this block wall.
What I'd like to know, is how much risk is it to one remove the two vertical columns of non-staggered block that are failing? I can see large voids behind it, where the dirt either settled or never got put into place very well. I am also curious, is there a safe distance that I should be able to dig out some of this dirt from the fireplace stack so that I can turn the 90 into the dirt of the crawl space?? If I leave about 18-24" of dirt between the new section of wall and the fireplace, should it hold up? Like I said I won't be going too far, just a course to a course and a half of concrete block.
Laying the block isn't a problem, as my neighbor is a brick mason and he'll be doing the layup of the block and they'll be solid filled with steel and concrete. I'm just curious what the general consinous is about removing dirt in the crawlspace near the chimney stack. From what I can tell they poored a concrete slab(s) under the stack, then laid some block, then started building.
I'll see if I can get some pics if it would clear things up any....