In the back "L" of the basement, the foundation walls do not go down as far as the rest of the building. We need to provide lateral support for that soil beneath these shorter sections of wall so that it may retain its high compressive strength. We are going to do this by pouring a 6" concrete shelf to hold any exposed earth back.
(Imagine standing in a box of tennis balls (random analogy). If you were careful and maybe had some help, you could probably stand on top of the balls. Now imagine you are standing on top of box of tennis balls and somebody removes one side of that box. What is going to happen? The tennis balls are going to explode out the side and you are going to fall on your butt. In order for the tennis balls to have any compressive strength to carry a load (you) it needs lateral support to hold it all together (box). Get it? By excavating below the foundation wall, we essentially just removed a wall of our box.)
red = exposed earth
6" thick concrete shelf is poured around the sections of wall that would have exposed above the top of the finished slab.
The poured slab protects and reinforces and remaining sections of exposed earth.
This is what the final product is going to look like (except the translucent brick). Notice the 6" step? We decided to use a step to reduce the amount of exposed earth that we needed to pour a shelf for.
This is the section of wall before the shelf was poured. There was about 20" of exposed earth below the bottom of the foundation wall. Yikes!
The following pictures were taken today of the forms for the concrete shelf being removed:
This ridge vent material is going to provide us with a little space to let any liquid water from the foundation wall to drain down, bypass the concrete slab, and make its way to the drainage system below.
James and the Site Structures guys going over sump pump piping.