foundation erosion/concrete (drainage) work needed
 

ok i've ignored the problem long enough. we have a walk up basement on the side of our house, about 12 concrete stairs long. last year a couple small holes appeared where the grass meets the top landing. i figured it was merely little animals burrowing but the holes have gotten bigger. yes i'm an idiot for letting it go so long because poking around today with a flashlight, mirror, and long stick, the 2 holes appear to lead to a friggin cavern beneath stairs/landing. i'm not even sure how far down the eroded open space goes, maybe below the whole staircase? below the house???

anyhoo, does anyone have any recommendations as to someone who can handle this as well as some concrete work down in the well itself - i want to open up the sump drainage hole so that it stops from getting clogged and flooding my basement all the darn time.

btw i'm in germantown md if anyone knows a local outfit.

I do not have a contractor to recommend, just some info to provide. The voids are likely from the soil settling over time, and/ or surface drainage. Not much you can do except try to pack some soil in at the top, regrade at the top and maybe extend any downspouts away (pics would help -- I have no idea which -- if any -- of these apply in your particular case). You can also hire a mudjacking company to come out and core through the stairs in a grid pattern and pump a flowable grout underneath, but good chance the soil will continue to settle and after a short period the grout will no longer be in contact with the stairs. BTW, this is not uncommon; I have the same issue at my house, and it is compounded by the marine clay that was in the soil used to regrade/ backfill. The voids under the carport slab are even worse!

If you want to go the mudjacking route, go to the BlueBook web site and look for a DC-area contractor. That is one of the contracting categories.

Cant help with the contractor but I had a similar issue. Talon is dead on about the fix, excavate and pack with material. Spend a few minutes with a shovel to see whats going on. Thats all anyone can do really. Good luck. Until the base material is packed hard anything that goes on top will settle, concrete, foam, soil...

thanks much for the info, fellas. ugh, i wonder if it's a result of our crappy builder or simply the soft, clay-ey soil. in addition, the inherent drainage situation certainly doesnt help - i'm at the bottom of a street and about 5ft lower than the house next to me so i get all the run off. the yard is graded somewhat around that area but when these monsoons move through, the grading just can't deal with it. and neither can my sump drain with all that water coming down the stairs (as well as spouting through a couple small holes at the bottom of the stairs, which makes me think the void underneath is HUGE).

2 holes visible in pic, on left and right of landing.

Attachment 49618

Definitely add some soil around the top of the stairs so it slopes away. Builders rarely compact backfill properly agaist foundations as they do not want to risk causing cracks; that leads to settlement issues over the next dozen or so years. clayey soils makes it even worse if there is marine clay content, as that material shrinks/ expands; don't expect it to ever settle/ compact and be done moving. Marine clay is grey, so if you only ever see reddish clay when digging around in the yard that may not be an issue.

Also, as stated earlier in the post, make sure the drainpipes are pushing the water far enough away from the house. We had water "seeping" into the basement until we put in trenches with plastic drainage pipes . Moved the water coming off the roof another 8 - 10 feet away from the house and the problem was eliminated. (the larger the roof area the more water that will be coming through the drainpipes)

Got the same problem at my house under the rear stairwell. Back fill settling. Since I moved in fifteen years ago I've been occasional filling with dirt, sand, stone, ex-wives, etc. each time after another void appeared.

Maybe you've got a spring under there. Artisan beers are all the rage these days! ;)

I bet you can back fill with pool sand then top with regular dirt. The sand will flow and fill voids and as the soil continues to compact the sand will continue to back fill. After time the sand will silt up and lock in place if there is water flow through it. Repeat as or if needed. Mud jacking is more for lifting slabs and repositioning walls.

'Mud jacking' is a grout injection technique that, as VG says, is mainly use to raise settled items. If you inject the grout to fill a void/ stabilize it is not mud jacking. However the contractors who do the grout injection work are generally listed as 'mud-jacking' contractors.

With the sand idea above keep adding as the sand settles (vibration will cause it to consolidate). But sand is quite porous so until/ unless it gets clogged with fines the river will still run through it :-)