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diggitydog 08-30-2006 11:26 AM

Sink hole under garage slab.
A small gap has developed between the asphalt driveway and the concrete slab in the garage floor of our home. I stuck a stick down in there, and there is a void that is about 18" deep!

Who knows how wide or long the thing far the garage floor has withstood and not crumbled above the void, but some surface cracks are developing throughout the floor. The home was built in 1978, but I've only owned it for a few years, so I don't know how long this void may have been present.

Must be some water getting in there and a sink hole has developed or the soil was not properly compacted when built and has settled. I live in Minnesota and am concerned about freeze/thaw cycles that wreak havoc on asphalt/concrete.

Just wondering what to do???

I plan on adding a third garage stall within a year, so I will repaving the driveway at that time. In the meantime what actions should I take?

Thought about pouring asphalt patch down in there, but that is pretty dense stuff to work with and may not fill the entire cavatity. Plus, the patch is probably not designed to fill such large voids. Also, thought about pouring concrete slurry to fill the void, but am worried about how the dried concrete fill will float with the slab (that is probably not freefloating) and the driveway during cold winters/hot summers. Couldn't the interaction between the slab, driveway, and fill material I choose lead to heaving, cracking, and crumbling where they all come together?

Thanks in advance for any advice!

joasis 08-30-2006 05:02 PM

You might call around to a concrete pumping outfit, and see if anyone in your area does a process called "mud jacking", and see if you can track them down. It won't be cheap, but short of a demo on the exisiting floor to open it up for compaction and repair, you don't have a lot of options. You don't know of a water leak in the area, do you?

diggitydog 08-31-2006 09:04 AM

Thanks joasis for the reply,

No, I don't know of a specific water source, but the asphalt does bulge a little just in front of the garage, so there may not be enough of a positive grade to drain it. The grade is not negative though, either. I'll have to out there during the next rain and observe.

I was hoping not to have to call a "jacker", but it seems that may be the only option.

Seeing that I plan on tearing out the asphalt driveway sometime in the not too distant future, should that alter my plans any or open up my options?


joasis 08-31-2006 12:49 PM

Nope, no other options I could suggest....hydrostatic pressure is the only way to fill the void, and concrete has enough weight and mass to compact the area....of course, this is not my area of expertise, but a knowledgable jacker can tell you if it will work.

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