Is it safe to excavate soil next to concrete slab?

Question

I'm looking to regrade the soil around my shed so water doesn't continue to damage the sill plate. The concrete slab is barely above grade, so I'm looking to remove soil to expose it another 2-3 inches. I'm concerned about potentially undermining the concrete slab by removing soil around it - Is it safe to remove the soil and expose the slab another couple of inches? Will this cause any issues with the foundation seeing as it's been this way for 18 years?

On the opposite side of the shed which is the last picture, the slab is exposed a good amount and there's no water damage to the sill plate. The shed is on a sloped hill, hence why that side is higher above grade.

Any input would be greatly appreciated.

Answer 1

The only issue would be if the regrade created a soil erosion problem that eventually removed soil from below the slab. As long as the compacted soil stays below the slab, you're fine. Assuming that the image's slab is level to the horizon and assuming that the soil conditions shown apply downstream (especially at any corners), your grade shouldn't be steep enough for an erosion problem. Something like grass with many shallow roots to stabilize things would be nice insurance.

For bridge piers in rivers, erosion vulnerable river bends, etc., "riprap" (a pile of boulders) is used to prevent soil erosion. It's a fun word to say. I seize any opportunity to utter it. If soil erosion seems to be developing after your regrade and you want bare soil for your landscape, then the solution is some kind of riprap. Don't freak out over any tiny sign of soil erosion, though. If your soil is a little silty, then some silt may wash out and leave behind a coarser soil that will suppress further soil erosion.