Corner of house and foundation breaking away

[umby63]

My mother's house sits on a cinder block foundation and brick wallls. The ground around this 1951 two-story bungallo is clay. She recently had her basement waterproofed and it began leaking again this past spring. When I took a closer look it appears the whole southeast corner of her house has stepped cracks leading from the center of the eastern and southern basement walls leading up, to just under the gutter of the southeastern corner. It appears as though the big maple tree about 15 feet away is drawing moister out of the clay cause it shrink away from the house. I believe the footings beneath the eastern and southern foundation walls have broke and now this corner is free from the house. In desperation I instructed her (against all intuition) start waterting the ground around this corner in an attempt to rehydrate the soil. This has had some success and the eastern cracks have closed very slightly. This can't go on much longer so does anyone have any advice?

[pushkins]

15' certainly isn't far enough away from the house for a maple tree and you could very well be right with your assumption about the maple drawing out the moisture from the clay.
With that being said, the cracks your describing and your diagram indicate foundation failure no matter what the reason. This corner of your mothers house's footings have dropped causing the staggered cracks that meet at the top, a 50's vintage house with poor footings would have failed way before now, so you can at least rule out insufficient footings as a cause.
Has it been a drier than normal year? Can you see any roots from the maple at or around the cinder block wall of the house? (roots can often be the cause of foundation problems, especially from maples and oaks)
Just how big/wide are these cracks?, is the brick work around the cracks still fairly level either side of the crack?

[umby63]

Thanks Pushkins,
No it has not been dryer than normal, in fact we had a relatively wet year in SE Michigan for a typical summer. No I can't see any roots, but we had her sewer line replaced 6 years ago (exits the south side of the house within that broken corner chunk) because of root invasion. And the brick tiers appear to be level outside of the the broken corner. The crack in the south wall is about .75" in width and the one in the east wall has reduced slightly to around a .25" I have placed tape across both cracks in about dozen spots up and down the wall, marked the gaps with pencil, and dated the piece of tape in an effort to see which direction things are going.

Here's where I want to be careful not accuse: Five years ago we had her basement waterproofed. The crew dug up around the outside of the house and down to the footings, wrapped and tarred (or appoxied) the foundation, they also replaced the drainage tiles and cleared the taps. They back-filled the trenches with pea-gravel and topped it with a couple feet of soil to maintain a buffer from heaving clay in the winter. But here's where I think the problem came from: The foundation walls were cracked and bowed into the basement in three different places. At each crack they placed I-beams vertically against the walls, pressed them out with jacks and once they felt the walls were plumb or whatever, they then plated and cemented these I-beams in place. One of the spots they performed this procedure was on the south wall within what is now the broken corner. They did not do this on the east wall however. Could this have lead to the footing failures?

[pushkins]

The practice of adding I-Beams to straighten basement walls is fairly common and in reality quite a good idea and provided they are installed correctly an ideal solution.
A couple of things that do stand out to me though, is the adding of soil to backfill the walls and the addition of "pea" gravel, are you sure they used "pea" gravel and not much bigger gravel (drainage gravel is around 1" ish in size) to back fill over the drainage tiles?. The other would be backfilling with dirt, most often the back fill should be drainage gravel up to say 6" below grade level.
Gravel cannot compact, so it makes for an ideal fill material under footings that have holes left from old tree trucks etc...for example and for back filling against basement walls especially in heavy clay soils. In your case the dirt settles, the clay expands and pushes the dirt against the basement wall, same thing as if the clay went all the way to the wall. With the use of rock as a back filler, the clay expands, pushes the rock, the rocks wiggles around and finds a new place to sit....very little wall pressure.
One other question..., have you seen water coming out of the drain tiles? or water coming into a sump pit in the basement to be pumped away ?

[The Builder]

It would have to be seen to get a really good idea of what the problem could. But from what you have mentioned it sounds like tree issues. And also in addition to what you mentioned about the basement waterproofing, it would be a good idea to excavate around the damaged area of the wall to really get a good idea of whats going on. But to me it reallysounds like tree issues. I seen one instance when a tree (not fully grown as far as height) busted through the masonry wall of the house. Once the trees start and get pretty big in size, its alot of trouble. But get a good idea of what the situation could be, and then excavate. Like I said I and the others would have to get a good look at it to give you a really good pinpoint judgement, but from what you write about the situation we can give you good ideas on what the problem could be, as well as helping you toward a solution.

[umby63]

Thanks Builder and Pushkins. Pea-gravel may be an invalid description of what was used to backfill, from the tiles up, to just beneath the grade, where the rest was fillled with top soil; I think about 6" or so. No I cannot see the drainage tiles, nor does she utilize a sump pump; it's all gravity fed to the city-sewer out front. I'll try to contact the contracter to see what he used for backfill.
What are her options going forward? Is piering-up the foundation the only approach? And what does that entail? Cost? I (radically) invisioned wrapping the entire house in a cable (at grade level) with angle irons driven down around each corner for protection (see the original drawing) to hold the chunk in place! This wouldn't keep the chunk from dropping but may arrest any further lateral movement. Can you sense the desperation?

[pushkins]

What your looking at is basically foundation jacking, to do this thy will dig down to the footing and then under it, there they will place jacks to lift the footing (and therefor wall). Once they get the footing to where it is supposed to be they will add concrete piers under the footing to support it, this might entail them digging down a little further and installing pre made concrete footings. They then set the foundation back on top of the new foundation and back fill the hole, then they should seal the cracks in the mortar all the way up the crack and down the other side. It's a fairly simply operation but not one for an amateur, make sure you use a reputable firm, ask for references and check them out with your local BBB.
Without seeing the job a rough guide for the work cost could be as little at $3K and go upwards from there.
What you need to stop is the further dropping of the foundation, there would be no lateral movement if the foundation wasn't dropping.

One thing though, are there any cracks on the inside of the home around or near this effected corner ?, like cracks in drywall/plaster doors not closing well ?

[umby63]

"One thing though, are there any cracks on the inside of the home around or near this effected corner ?, like cracks in drywall/plaster doors not closing well ?"

Yes to cracks, but doors and windows closing ok (for the moment). The basement cinder block walls are cracked from floor to ceiling and in many cases right thru the block (not just the joints). On the first floor there is some cracking at door corners and window frames in the plaster (no drywall/sheetrock in this house). But the cracks I speak of have been around for decades in some cases, and if newer, were exacerbated by the wall jacking during the waterproofing effort. What I am the most afraid of is this: There are two east-west oriented I-beams sitting on top of the foundation/cinder block walls that the first floor deck and (by default) the rest of the house sits on. A .75" gap has appeared beneath and between the east end of the southern most I-beam and the top of the basement wall (part of the "falling/broken chunk"). I don't know much about this stuff, and I don't even know if these beams are level; but I am sure if they go out of plane with each other you will be able to hear the cracking plaster on the first floor...
I'm thinking of wedging an axe head (without handle) in between these components as sort of a shim to keep the beam from falling and twisting the house. Don't know if this is a bad idea, don't know the ramifications. Also if that chunk somehow pushes back up into place with that shim there, it could have an opposite effect on the first floor deck with equally bad results. Please advise on the shim thing...

[pushkins]

Call the foundation people out to have a look at the home, most definitely any beams in place should not be floating, so I'd treat this as a sooner rather than later task.