Digging down below the bottom of a foundation wall is risky without adding structural support
In this quick REEL Remodeling episode, Michael Anschel describes the foundation's footing situation in a 100-year old house in Minneapolis, MN: there is none.
"All right, so we have a unique condition here. This foundation has no footing at all. In order for us to lower the basement floor, we've got to build a structural curb. That's this piece.
We've got some fabric over the earth, which is dug at a 45-degree slope. This allows the foundation to stay stable. Then, we have the curb filled with rebar that comes out into the slab.
This structural slab is going to hold up the curb, which is going to hold up the foundation. So, it's one big structural assembly."