Why Basement Walls Bow
Basement walls bow when the soil becomes unstable due to pressure.
This can be because of water, extra pressure from a driveway, flooding, or general settlement of the soil around the property. The pressure this creates can bow basement walls exposing cracks in basement. This is bad because once there are cracks it becomes increasingly easy for the basement walls to bow even more. Real estate values can tank when basement walls are bowed.
Luckily, it's not an unfixable situation. You can repair almost any basement wall. The question becomes what cost is associated with the repair.
There are simple solutions like bracing the walls. And then there are more permanant solutions like digging all the dirt out around the basement, repouring the foundation, and basically starting over.
These are essentially the two extremes that can happen when fixing basement walls.