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Gap bet theween concrete and soil

967 Views 3 Replies 3 Participants Last post by  garrett1812
After digging next to my concrete patio, to see the extent of a rodent den, I discovered (besides that the rodent den was not too large) that there is about a 1" +/- gap between the bottom of the concrete and the top of the soil.

From the hole I dug I could insert a tape measure about 6ft deep under the patio. I do not know if it is localized here, or if this condition exists all around the patio.

Any idea what caused this? Erosion? Poor compact of soil before pouring?

And more importantly, what needs to be done to fix it?

Normally the patio is just used for a dining table and chairs, but I have been eyeing a stone grill kit from Menards, which is approx 4000lbs in stone. I do not want to get this and make it crack. The patio is approx 1.5-2 years old.

Thanks for the help!


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Soil settles over time under concrete. Even properly compacted it will do that. I wish we had digital photography years ago when we cut coolant trenches into the floors out in the plant. Building was built in 1949 and 45-50 years later, there were voids under the floors in some spots you could crawl into. Realizing we had heavy equipment sitting on these floors, we decided to have a company come in that did a sonar check of the floor and then pumped grout into all the voids. The interesting side effect from all of this was the 5% drop in ambient noise in the plant.
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