Leveling ground under old shed

Question

I have an old large shed I'm trying to get back into shape. The building is about 50 years old and 16'x48'. One of the long sides had sunk in the middle by about a foot, giving that side a bit of a 'V' shape. I've actually jacked this side back to level with a few beams and am trying to figure out how to support it permanently.

The original foundation was a shallow concrete perimeter, about 1' wide by 2' deep, right below the shed walls. There was a single course of cinder blocks placed on top of the concrete, and the walls built on top of these. The concrete seems to be in good enough shape on 3 sides but has completely crumbled on the side with the sunken middle.

My idea is to build a short retaining wall, about 2 feet out from the raised side, to level off the 'V', fill the inside with rubble/gravel, and set the shed back down on it. I feel like the wall could be simple as it doesn't need to hold much back - maybe some PT 6x6s or 6x4s driven a few feet into the ground every 4 feet and then PT 2x8s behind them. Does this seem like it would work? Is there a better way?

Answer 1

Rather than build the retaining wall would it not be better to break out the old and crumbling foundation clean out the area. Then build up the necessary forms to permit new concrete to be poured. From the sounds of it this shed wall is easily accessed from both the inside and outside and so getting the forms built and the concrete poured should not be too difficult.

This solution seems like it would be a lot better than stealing two feet of width all along one side of an only 16' wide shed.

Answer 2

Your solution would work, as would Micheal Karas', but this is just a shed, not a major piece of architecture.

I think I would work some more cinder blocks or bricks in under the jacked up edge (possibly scraping away the ground to make room). This has the major advantage that if the ground crumbles a bit more when you put load back on it, you can repeat the process relatively easily.

Answer 3

The crucial question is why the piece of foundation crumbled, i.e. what kind of cavity is beneath it. Exploring that may then lead to a good solution. I found out that this worked for me when I was leveling sloping ground for shed's foundation. We all want things quick, but thinking things through usually go a long way.