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I have an issue with soil erosion below the front corner of my garage floor which has caused a crack to form and a piece of the slab (~4sq.ft) to sink. This in turn is affecting the portion of the outside wall which is supported by the area to sink/lean.

The garage was built by previous owners and is a simple concrete-block wall with a brick veneer on the outside. The part of the front wall that is currently sitting on the cracked piece is only about 3' but I imagine it's likely that the void underneath is larger.

I'm currently reading up on concrete jacking, but am worried about the additional load of the wall on the slab. I know that it's typically recommended to wait 24h before driving on a jacked slab, so would the concrete jacking process have enough pressure to fix my situation?

If there's another approach that I might be missing, I'm also open to suggestions.

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    This is one job I leave to the Pro's. It can be done and back filled. A Pro would have the correct equipment and be able to back fill. The erosion problem needs to be solved or it will happen again. If it was a simple slab I think a DIY person can do it fine but a load bearing wall added to the mix that is driven on would be out of my comfort zone. – Ed Beal May 20 '16 at 14:06
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    Agreed. If concrete jacking is possible, I'll leave it to the pros. I was hoping that someone in the biz might be able to give me advice on if this is possible or not, or otherwise how best to tackle the situation. I updated the question to expand a bit. – nageeb May 20 '16 at 17:16
  • I have seen this repaired by: 1) injecting sand under the slab and 2) stabilizing the soil by building a retaining wall which was 10+ feet away and filling. – wallyk May 20 '16 at 17:22
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    It is possible. They drill holes and pump mortar under the slab. I have had multi story chimneys leveled that had started to pull away from the house. Expensive but WAY cheaper than redoing the chimney, slabs are easy for them the wall on top may add cost but I am sure they can do it. (the guy I use uses mortar some use everything from sand to ash) – Ed Beal May 20 '16 at 17:23
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Here in my town, I have seen foundation repair that is great for loss of substructure support, such as soil compaction or erosion. What they do is bore a hole in the slab, and inject expanding urathane foam into the slab underside, as they watch the slab level and cracks. What happens is under thousands of pounds of pressure, the foam replaces missing soil, and litterally lifts the sagging slab. Since the foam is like a liquid, it flows to where it is needed, and supports very evenly. Once the engineer is satisfied he has the right amount of list, they turn the machine off, and shut the valve, but leave the fitting connected. They wait for the foam to harden, before they disconnect. At that point, the repair is pretty much permanent, at least until more erosion or settling causes the need to repeat.

As long as there isn't a place for the foam to escape, this works great. If there is a sinkhole, or an opening that lets foam out, they may have to inject, pause for a day, and inject again... till they get the needed results. Obviously this is for a slab on or in the soil. For slabs poured over basements, screw jacks and perhaps beams are installed in the basement.

But this is a job for a foundation repair expert. This is one of those areas a do-it-yourselfer can do more harm than good. A foundation repair company will have insurance for liability, in case something goes wrong that is his fault. If you do it yourself, you could make things worse, and there is little limit to what worse means when it comes to supporting a house on a failing slab.

  • This is often referred to as Mud-jacking. – Ken Jul 18 '18 at 4:26

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