House possibly built on a bunch of stumps and garbage

File this under "fun with home ownership".

My in-laws had a test agency/engineer out today to run ground penetrating radar on their floor slab to identify points to do test borings. They identified 3 spots with suspect zones, which will be bored shortly to see what's under there.

House is in northern Floriduh, about 10 years old. The community's developer and builder are long gone, legally and figuratively.

My theory is that their floor slab (on grade) is sinking because the builder buried a bunch of stumps IN the house footprint. In Atlanta, the builders are kind enough to do this under the driveway.

It's possible that it simply wasn't compacted enough. The testing is to try and determine if mud jacking will work.. or find out if that'll only provide temporary relief. It's down about 3" in 15'. Fairly alarming.

Anyway, assuming organics are decomposing and the slab settling at an alarming rate..

And knowing you can't sue the building inspector for failing to get out of the truck....

I am curious if this is something that might be covered by homeowners insurance.

I don't have the policy in front of me - just looking for clues. Anybody been through this before?

No advice and good luck. E36 M3 like this makes me want a condo.

In reply to OHSCrifle:

In my experience the likely hood of an insurance company paying this is very slim. But I have been surprised in the past.

On a related note, and ironically in Atlanta we had a warranty call on some pilings that were installed about five years prior, on a garage. Upon excavation I found that the garage was built on a massive dump pit. I'm talking full size tree's just 6" below footings. The pilings should have never been installed because there was no way to penetrate through that crap with a pressed piling. However the original crew installed them so we had to try and deal with it due to the lifetime warranty. I was able to get it lifted but it was still sitting on a big pile of decomposing trash and I have no doubt that it would be an ongoing problem for the life of that structure.

I know what was installed at that particular job was not the correct fix for that issue. I'm not familiar enough with mud jacking but I keep coming back to the fact that it's still sitting on material that is going to continue to decompose and change with time. It's going to be an ongoing issue unless the junk is removed and something solid takes it's place.

Trees in slab- unlikely.

Uncompacted soil under slab- extremely likely.

I got a call once from a lady who had a hole in her floor. Sure enough, when I looked, she had a big hole in her bathroom floor. Big enough for me to climb in.

I looked around with a flashlight, then realized it wasn't a crawlspace, it was a slab. Or maybe I should say is wasn't intended as a crawlspace.

The soil had settled about 20" throughout the house. I could see all the way across, and could have crawled under it (if I was that stupid).

I walked into her Dining Room, and jumped (a little). The concrete floor bounced like a trampoline, and her china cabinet swayed away from the wall. The house was 3 years old.

I told her I couldn't help her, and that she should call her attorney.

If I am right, mudjacking should indeed help. But this is not gonna be cheap. I hope your insurance helps. Good luck- keep us posted!

It's possible it may be covered however it really depends on the policy though.

I tend to agree with SVreX, I've seen many more issues with loose fill/uncompacted soil in the over my 16 years of doing foundation repair for a living. In fact my post earlier is the only instance that I can think of with that issue. I've seen tons of stupid things though, it was an interesting ride.

Foundation repair in Central Texas should be a never-ending growth industry, from my observations.

I think it sounds more like shifting soil, etc., than buried trees, but I'm no expert.

When I had my shop slab done, I called around to some slab contractors. "We'll bring in a hundred loads of red dirt, (at $$$/load plus $$$/load transportation), tamp it down, dig out a trench, pour a footing, come back and set cinder blocks, then pour the top." "Won't that crack?" "Well, all slabs crack." "Thank you." Click. I called my friend that retired as a civil engineer with the Texas Highway Department and said, "Doc, how do you make a slab?" He said "Here, I'll email you a scan of the Texas Highway Department's specs for one." I built it that way. I think I have the only uncracked slab in Arkansas. I go by people building them with fill dirt and cinder blocks all the time.

In-laws are being told to figure (fearing) about $6-12k to stop the bleeding, but it is purely a guess until the test boring reveals the actual layers in the cake..

The only good news is that the roof (trusses) doesn't bear on interior walls, and it's a one story house. And the floor settlement doesn't extend all the way to the exterior walls.

I really hope it's proven to be poor compaction and not a bury pit. Thats what the evidence points toward so far.

Cement grout or urethane injection should fix the former. If it's organics, they're bummin'.

Nick,

Aside from entire neighborhoods in ATL suburbs, each with a tree/trash "bury pit" under the concrete driveway.. being fixed by excavators and dumpsters to the tune of $10-20k each..

The craziest one ever I saw was a restaurant down on Hilton Head Island. New construction, with a Geotechnical report that recommended to use driven timber pilings. Several went in as expected. Then one hit something weird. Them another. Then another. The GC brought in an excavator and started probing.

There apparently had been a junkyard on the site, and a metric E36 M3 load of VEHICLES had been buried.

neon4891 wrote: No advice and good luck. E36 M3 like this makes me want a condo.

It makes me appreciate living somewhere where houses have "foundations" instead of slabs.

In reply to OHSCrifle:

Bury pits on residential lots in GA have been illegal for over 20 years. Even when they were more common, the entire point was to put them where the house was not.

Improper fill compaction is very commonplace in residential construction. There are still no regulations requiring compaction testing or boring for residential work (although testing is typical in commercial work).

You are describing a typical residential compaction issue. Footings are tight because they were dug a little deeper and built on undisturbed earth (which is standard method). Center sinks because it was filled without compaction.

I'll give 95% odds there is no organic matter.

Knurled wrote:

neon4891 wrote: No advice and good luck. E36 M3 like this makes me want a condo.

It makes me appreciate living somewhere where houses have "foundations" instead of slabs.

You mean basements instead of slabs.

All houses have foundations, and all of them can have compaction issues (including basement houses).

In reply to SVreX:

troof

In reply to SVreX:

Agreed. I sure hope you're right, for their sake.

SVreX wrote: In reply to OHSCrifle: Bury pits on residential lots in GA have been illegal for over 20 years. Even when they were more common, the entire point was to put them where the house was not. Improper fill compaction is very commonplace in residential construction. There are still no regulations requiring compaction testing or boring for residential work (although testing is typical in commercial work). You are describing a typical residential compaction issue. Footings are tight because they were dug a little deeper and built on undisturbed earth (which is standard method). Center sinks because it was filled without compaction. I'll give 95% odds there is no organic matter.

When I was 14 I worked for a general contractor. My main job was cleaning job sites. More than a few times he handed me the keys to the bobcat and told me to backfill a foundation with all the garbage on the lot. I know of one house in particular that the front porch began to detach after the junk started to settle. I didn't know til years later what he told me to do was probably illegal.

All of this scares the heck out of me with new construction...

Enyar wrote: All of this scares the heck out of me with new construction...

Me too. I've had way less issues with my 1959 house than I did with my 1989 house.

I've had way less issues with my 1949 house, than I did with my 2008 house, which we bought new.

Based on your replies, I'm pretty sure I'd want to be my own on-site general-contractor if I ever have a house built.

In reply to petegossett:

That may not be enough.

I would bet 90% or more of Residential General Contractors do not know much about compaction and soils.

I've spent a lot of time in both residential and commercial construction.

Standard compaction practices in commercial construction don't even exist in residential.

For example- as a Commercial Contractor, I wouldn't leave a trench open overnight. You do what you can, then fill it up, and re-dig the next day. Every trench is done the same way. When permanently backfilling, the trench is compacted in 8-12" lifts with a hydraulic ram packer, not a vibratory plate compactor.

Residential work would think nothing of digging a trench and leaving it open for a week while they tried to finish the work. During that time, it may rain a few times. The trench will fill with water, and the soil will be saturated. This is no longer a suitable building material. Commercial would dig it out until solid again (perhaps another 2'), then fill with dry good dirt, and compact in 8-12" lifts until you got back to where you were supposed to be.

When backfilling, residential will fill the entire trench full depth with whatever dirt they can find (which might be topsoil with organics), drive their backhoe wheels on it, then run a plate vibratory compactor over it (which will only compact the top 4" or so and make a crust over the uncompacted base).

It's a different world (at a substantially different cost).

The best insurance policy on a new house would not be relying on a General Contractor, but hiring an independent soils engineer and testing company to monitor the fill and compaction. They inspect the soils type, probe with a probe rod, complete proof rolls, and bore when necessary. They actually watch the work being done, and write an in-depth report. It would add a few thousand dollars to the average job (assuming the sub-base was suitable- if not it will add tens of thousands to undercut the bad soil).

Commercial sites use soils engineers on every job. Residential sites literally never see them.

In reply to SVreX:

Awesome info, thanks!!!

Im going to find a way to apply hover board technology to houses and then foundation problems will be eliminated.

I can't believe no one posted something like this yet.

Did you tell them you are looking for the cause, but so far you are stumped?

We can remove the word "possibly" from the title of this thread. Now there's proof...

Inlaws have the report from a Geotechnical firm. Investigation included..

6 hand auger borings (4-6' depth) and

1 hammer driven split barrel sampler penetration test (37').

If you've read this far and are willing to keep going, here is the cliff's notes summary of the test data..

Hand Auger Boring no. 1 (foyer)

2' band of fine sand with construction debris and trees debris from 4' to 6' depth.

Hand Auger Boring no. 2 (living room)

Sand and rock

Hand Auger Boring no. 3 (dining room)

6" band of sand with construction debris and tree debris from 5.5' to 6' depth.

Hand Auger Borings

No. 4 (outside front corner) No. 5 (outside middle end wall) No. 6 (outside back corner)

...all sand and rock

Hammer driven sampler test

0 -2' clayey sand with tree debris

2' -13.5' fine sand

13.5 -18.5' clayey sand

18.5 -33.5' clayey sand with limestone

33.5' -37' limestone

Report recommends:

Install underpins to refusal and anchor structure to underpins.

House did not settle at footings, only at 4" interior slab on grade.

I suspect mud or urethane "slab jacking" will provide a temporary fix while organics continue to decompose below.

Anyone know how to shore up a 4" slab on grade without cutting trenches and casting reinforced grade beams?

Jack up house, move to rear of lot. Dig basement. Move house onto basement. Win, other than the hundred thousand in debt.

This situation sucks, and somebody needs a punch in the head.

I'm sorry to hear that.

Slab jacking is probably going to be your best option. You're right about the ongoing deterioration of the organics, but I wouldnt call slab jacking "temporary". It could easily be a decade before any settling is seen again, but the slab jacking could also reduce the deterioration rate by encapsulating the organics and removing the head space and oxygen/ moisture.

What was the density like? Did they find big voids?

I guess the good news is that structural support points are in good shape since the footings are not compromised, it's just the floor.

It's not a good situation, but it really is exactly what slab jacking is designed for.