05:19PM | 08/13/03
Member Since: 08/12/03
2 lifetime posts
While investigating a problem with the air conditioning unit that resides in my crawlspace I discovered a more serious problem. I found that a small sinkhole has formed which runs under the footing of one of the cinderblock support piers that holds up one of the main beams under my house. I called a foundation repair company to come and check out the situation and was told that the pier has not failed and that it is still holding fine. The foundation company recommended just filling the hole with concrete. They said if the pier fails then a helical pier is the solution.
I estimate that the hole is about 20 inches deep and 20 inches wide and runs for about 24 to 30 inches. The hole is also filled with water. I have pumped the water out of the hole two times. Each time it has refilled with water overnight. We have had a tremendous amount of rain this summer and the ground is very saturated. I have verified that the water is not coming from a leaky pipe or the air conditioning unit.

My plan right now is to pump the water out of hole and then scoop out any loose or gooey slop. I will then immediately fill it with concrete. I estimate it will take about six to eight bags of concrete to do the job.

Does this sound like a good solution? Will the water in the ground mess with the concrete as it hardens? Should I possibly wait for the dryer weather to see if the ground water level lowers leaving a dry hole to fill?

I would appreciate any thoughts or Ideas.


01:29AM | 08/14/03
Member Since: 01/14/03
264 lifetime posts
If the pros have told you that the pier isn't in danger of immediate failure, and the hole isn't getting any larger, then I think I'd wait for dryer conditions before filling. Even then, I think I'd just fill with clean gravel. If this pier is under the house in an area that is tough to get at, and the hole gets bigger still, then an extra blob of concrete that needs to be broken up and removed and really lends no support to the pier will just be a nuisance at that time. The gravel will be easier to remove (if it's still there...)

There has to be a reason for the hole, and that reason will be underground, under the hole. The material that was in the hole has gone 'somewhere', and that somewhere is under the hole. If there is, or was, a cavity down there, perhaps it's filled with the missing material now. Perhaps not. New gravel in the hole can migrate down into that cavity if that's what nature has in store here. A blob of concrete will simply sit there and allow the earth under it to subside, and you'd never know until the blob goes down, too. And things will be really late then.

Keep and eye on it and call your pros back if things don't get better after you fill it.


02:11AM | 08/14/03
Member Since: 08/12/03
2 lifetime posts
The gravel idea sounds ok but I am concerned that I would not be able to compact the gravel enough to add strength to the undermined footing.

I also forgot to mention that I found some pieces of what looked like rotten wood in the hole. There is a depression that makes me believe that a log was burried under the crawlspace floor. This log probably rotted and left a void which may grown to the size it is now.

More Ideas are still welcomed.


05:19AM | 08/18/03
Member Since: 09/16/02
250 lifetime posts
Is the house new or old? They probably backfilled with any garbage that was left at the site. I think I would pour sand in the hole to fill it. It's cheap and flows easy. As far as the water, do you have gutters? Does the land outside your house slope away from your house GOOD. That's where most of the water comes from in a craw/basement. Do you have a sump pump? If not you can put a sump pump in a crawl space. I had a basement waterproofer come to a house I owned and I learned a lot from them about hydrostatic pressure and where water comes from in a crawl/basement. Didn't cost anything for the estimate and info.
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