Hello, I have a two story house with 4 foot deep footings and a floating slab.
I want to put in a underground furnace room on the back 'side' of my house, but I'm afraid once I start to dig below the footing depth, my foundation might shift, fall etc. My foundation has a slight problem, whom ever built the house put 2x4's vertically into the footing foundation. I assume they were part of the forms that were used in construction of the foundation. Anyway, they seem to be placed every four feet. Not only that there has been some shifting and cracks where the 2x4s have been places (almost like a controlled break). Is there anything I can do other than digging 2 feet (would two feet prevent a catastrophe) away from the foundation?

The foundation is 24 feet long, I'm wanting to build another foundation about half that length.