Brick Basement Wall Construction 2

[PSUengineer1]

Thank you for considering. I have a brick basement wall that collapsed (see attached photos). I have never seen this type of construction. Let me describe it. A basement wall constructed of brick abuts a crawlspace constructed of block (Photos 1 and 2). Viewing from a grate in the crawlspace block, the outside face of the basement wall is visible. Where I am confused is that the upper portion of the multi-wythe brick basement wall appears to be supported by a thin concrete slab that spans about 11 inches to the interior one-wythe wide wall that collapsed at the interior of the basement (Photos 3 through 7). The interior one-wythe wide wall is about 3 feet high. What is the visible air space in photo 7? The air space is too close to the floor slab for me to say it is the underside of the thin concrete slab that is about 3 feet off of the basement floor. Maybe there was a small opening there at one time prior to construction of the crawlspace? I did not have a fiber optic cable for my camera during site visit. Any insight on familarity with this wall construction would be beneficial. thanks, jimjxs263.

 

[JAE]

What this looks like are the many old houses I've seen where originally they had a perimeter foundation wall that extended down to a footing, perhaps deep enough to get below frost.
The house originally had a crawlspace under it.

Then at some point later on they decided to add a basement and dug deeper.
However, due to the somewhat shallow perimeter foundations they couldn't dig directly adjacent and below the footings or the footings would be undermined.
Therefore, they typically dig just inside of the perimeter wall to leave a "pyramid" of soil below the original foundations.
This leaves a shelf of soil around the perimeter and typically they would block or brick that up and cap off with a light concrete or grout closure slab (your shelf in the pics).

Unfortunately in your case, it appears that the lower brick/block wall wasn't properly designed to take the lateral thrust from the soil behind it and it collapsed inward.
Remember, there is no only soil behind the lower wall but also vertical load from the main perimeter footing behind it.

You need to reconstruct a proper retaining wall with the required footing under it - perhaps an "L" shaped retaining wall to avoid excavating under the perimeter footings.