get a structural engineer and SEVERAL quotes.

Get an independent engineer to help develop a remediation plan.

It is likely to take more than one engineering specialty.

A structural to determine what is moving, and very possibly a geotechnical engineer to evaluate soil conditions on the site.

Together they can help select the most cost effective repair.

What Brick said.

Sounds like the builder may have omitted the geotech engineer back in '88, but went with minimum req'd soil reports. Absent details, I'll say most likely a structural engineer was not req'd by builder because your foundation, max loadings, wall heights, etc. fit within the "plug and chug" solutions found in ACI handbooks.

I need to ramp up on foundation issues myself, and would appreciate details on this house--i.e. general location, soil type, slope(s) on lot, CONSTRUCTION METHOD, both foundation and above-grade. Also, what brand piers/pilings your quoting company plans to use.

Thanks in advance, and best of luck.

... the contour lines on your diagram, so belay my question about "slopes".

Curious: is the large square in lower right your garage? Did they not prescribe piers there because it's a separate slab, and though sinking, it's doing so more or less "evenly"??

Foundation-soil interactions... scary AND intriguing... a 2-fer.

Thanks for the advice.

Fixizin -- more scary than intriguing for me (ha!). We are not the original owners of the house but I suspect your theory about the build is correct. The house is in Texas - Dallas/Fort Worth area. Lots of clay soil here. Slab foundation. We've always said WHEN we have foundation problems, not IF.

We have a lot of retaining walls...guess where?? Right along these areas. The wall starts near the street at peaks at about a 4 ft height in the north west corner. Retaining wall continues to the north east corner but not quite as high...maybe 3 ft.

The company we're working with is Abacus Foundation Repair. They use millenium composite pilings (this doesn't mean much to me).

And yes, the lower right hand square is the garage. They tell me that it is intended to slope downward and that it's fine as is.

Here is a link that might be useful: abacus foundation repair

Fixizin, down here in the Dallas/Ft. Worth area we slope the garage floors about 1/4 per ft. for drainage toward the door.
There are literally dozens of reputable foundation repair companies in this area due to the nature of the clay soils, most people are advised to "water" their foundation perimeter during the summer to prevent the ground from cracking and damaging the foundations and slabs.
I would get estimates from at least three or four companies. Make sure the estimates give detailed information about what they are going to do and what guarantees they give. A lot of these companies have the structural and soil engineers on payroll. However getting some independent advice would not hurt.

shadetree bob - yes, an engineer is part of the process. Are you familiar with abacus? millenium pilings?

About the garage floor slope, "DUH" on me... (*blush*)

So above your concrete slab, are the walls wood-frame or concrete block or ICF or...? Just curious--trying to get a "feel" for your loads. What type of roof tops off the whole thing?

Anyway, here in So-Fla we have problems with sandy soil, so not sure how it applies to your clay. I will say your proposed pattern of pilings is typical of foundation repairs I've observed and/or paid for; i.e. grouped towards one corner.

I'm only hands-on familiar with "pin" pilings, which are basically just 3" dia. galvanized Sch 40 steel pipe, in 10' sections, threaded together. They are driven to refusal (DTR) with hydraulic rams; i.e. an L-bracket is hooked under the foundation, and a hydraulic ram pulls UP on that bracket (lifting the sagging part), while pushing down on the pipe, which passes through the bracket. When the piling gets to DTR, it is swaged or tack-welded to the bracket, the excess piling is cut off, and the whole affair is photographed and re-buried.

As for "Millennium Composite Pilings", I'm a tad suspicious that Abacus seems to be the only outfit ON THE PLANET (not just in TX, as they claim) who is using them. Also they show no pics and provide no details of same. Yellow (red?) flag!

As Bob suggests, shop around. Here in FL we have a one-stop state.gov website to check the license status of every firm and individual req'd to be licensed. I've weeded out a few hosers that way, e.g. guys whose licenses have been yanked, and are "glomming" on to their son's/brother's license, etc. Enforcement is kind of lax in FL, so I figure they must've done something SUPREMELY bad to lose their "paper" here. =:O

Thanks for all the advice and information! We'll keep talking to folks....

My home is in the DFW area, had work done on the foundation and I am very satisfied with the company called Advanced Foundation Repair. This is not spam call them they are trusted and good.

You only need 10 of the 12 pilings. You need the pilings that lie below the -.5' contour line. The 2 pilings located by the -.3' readings are not needed.

Wow... unless you are a P.E. with foundation experience--and have actually inspected this house yourself--I fail to see how you can second guess the on-scene engineer, esp. with the VERY limited data in this thread.

But hey, I don't want to miss out on the second-guessing fun. I'll posit that it IS an adjoining wall, and the ground does start sloping there from the high point, not to mention that's also where the slab starts settling. You do not know the details of the footer's construction, yet assume that a rather long *2-WAY* span can go unsupported, even at the corner, without cracking. My internet guesstimate says keep those 2 pilings... now where'd I put my official seal... ;')