Soil test for foundation-7 inch drop 2

[Lmalnati]

I own an 80 year old houes outside Chicago. The NE section of the house has sunk 7 inches. I have only lived in the house for 2 1/2 years so I do not know how much has sunk recently, but it appears to still be moving based on drywall, cracks on the cement blocks (vertical and horizontal), etc.

A structural engineer said I could spend 62,000 for Hydraulic push piers, helical supports,etc., but I am better off call in a bulldozer and selling to a builder. The engineer mentioned the settlement could be due to peat, however I have never had flooding and I have no sump pump. The fact I have had no flooding seems to stump everyone. The land is graded toward the street (NE)and rain accumulates in the street.

If I were to have a soil test and it showed peat underneath would this be expensive for the builder to correct this issue. The engineer says its a waste of my money to have a soil test done since the builder would perform a test anyway.

My fear is not only have I lost my property value, but now I have lost my land value. Any suggestions ? Please note I bought the house for appx 175,000

 

[fndn]

Relax-this happens all the time. You're better off spending couple of grand and finding out from a local geotechnical firm, what soil conditions exist in all 4 corners of the house and going at least 25ft deep, but no less than 10 ft below the bottom of unsuitable soils. From your post, It is possible that you have peat or other organics soils, with poor drainage and high compressibilty explaining the ponding of water near the NE corner and the excessive settlement. It is also posible that you have upper good soils and then beneath it buried compressible soils giving you a deep seated settlement. Geotechnical firms are very good for getting that soil info. Then find yourself a foundation repair contractor and show them copies of the soils reports and ask for an estimate. Call several contractors and pick the one with the most experience, and check their references. Realize that the best corrective solution comes from foundation repair contractors-they have experience and also have on staff soil or structural engineers.

 

[Lmalnati]

I did have one foundation company quote me appx $10,000 to install 5 helical to stabilize the foundation (NE corner). They would excavate to expose the foundation to depth of the footing, appx 8ft. It is guaranteed for 10 years.

I was surprised that they proposed this work, but never mentioned anything about a soil test. When I questioned him on a soil test being done he indicated it really did not make a difference since no matter what the soil conditions are I need to stabilize the foundation. He also indicated jacking the house up was not reccommended since it is a block foundation.

Based on your reply I will get a soil test, but can you provide guidance in terms of what solution I should expect from a fondation expert when they review my soil test results.

 

[fndn]

Lmalnati;
Once you get the Geotechnical report, it will indicate the corners or portions of the home that have unsuitable soils and the depth to good bearing soils(higher than 3000 psf). From there on, we can comment on the best solution for repair. Most likely, you'll need small diameter pipe pile or helical piles or similar. While you're jacking up the house, see if you can also replace the perimeter drains, and also check that you have backfill soils draining away from the house. It will be interesting to see what soils are present.

 

[Lmalnati]

fndn;
Thanks for the reply. I have a proposal for a soil test so I will start the process of having the test done. I will then post the result and see if there any suggestions.

 

[Lmalnati]

fdn;
One item I left out. The soil boring proposal says; Four exterior test borings extending to a depth of 15 feet below grade, drilled by a truck-mounted drill rig, sampled at 2.5-foot interval to eight feet, and then at continous interval to the end of test boring. This would be modified once foundation depth information becomes avaialble.

The program will include Attenberg limits, shrinkage limits, unconfined compressive strengths and natural moisture contents for basic soil classification.

I noticed in the above post it recommends 25 ft. Do I need to request that the engineer do borings at 25 ft rather than the proposed "15 feet below grade".

 

[fndn]

Yes, we need to go below the problem soils at least 10 ft, so as to make sure we're not on thin layer of good soil. With a basement, you're already at 8 ft below grade, and only 7ft remaining to account for poor soils and the good soils beneath that is a little tight.

They charge by the foot, after 15 ft, so it will cost us more, however we will know for sure the depth to good soils. By the way, if at 25 ft, they're still in the difficult soils, they have to go deeper to find the good soils. So the best thing is to ask them to go 10 ft into the good soils.

Now, since soil profiles vary, it is possible to get two 25ft deep borings, and two shallower ones. Therefore averaging closer to 20 ft.

With this boring information, your foundation contractor, can use the exact length of piles for retrofit, and you'll be able to make up some cost savings.

 

[Lmalnati]

Fndn,

Can you explain to me how I make up some cost if the foundation contractor has the exact length of piles. Are you saying if I did not have the soil test go 10 ft into good soils the foundation contractor may have to do some guess work ?

Thanks again
Lmalnati

 

[Lmalnati]

Fndn,

Also I did find the below in the Structural Engineer report;
"The foundation wall consists of ten courses of concrete masonry units for a height of 6'-8". The south face of the foundation is exposed approximately 3'-4" to 4'-0", from the west to east ends, respectively. This leaves a net below grade CMU wall of 2'-8". Allowing for a ten-inch footing thickness, the foundation bearing is approximately 3'-6" below grade. Minimum protection against frost heave is 3'-6"."

 

[fndn]

Lmalnati;

Ok, so you have a partial basement or also called a lookout. Then in the rear exterior wall, they will need to drill borings, and still go below the bottom of the poor soils, but it is possible that the 15 ft boring depth you stated earlier maybe enough. It all depends on how deep the problems soils are deposited. However, is the North side of the house then 6'-8" walls? In any case, ask for a good investigation and choices in their recommendations.

 

[Lmalnati]

fndn,

Yes the North side of the house is 6'-8" walls.

I will hope that within 15 ft they hit good soils, but I am still going to ask them to go 10 ft into the good soils.

While talking to the structural engineer he said the soil test could prove that my issue is due to something as simple as the Dutch Elm (80 ft tall) that is 11 ft away from the NE side of my house. How would a soil test prove this and could it account for a 7" slope ?

 

[fndn]

Let us see what the complete investigation report yields. With a full picture, it easier to rule out something, and weigh in the facts.

 

[Lmalnati]

I had another soil engineer stop by to write a proposal. He suggested only the problem corner be bored. He said the "typical" signs of peat problems did not appear from viewing the property and the inside of the basement.

However, he does not have any other explanation for why the foundation is on a 7 inch slope unless there are poor soils or if it was constructed that way 80 years ago (highly unusual).

What is your thought on the 1 vs 4 borings. Whether I have 1 or 4 borings done will I be able to answer the following question; Is my foundation stable ? Sorry to be a worry wart, but this is my retirement egg.

 

[eric1037]

I would have at least 2 soil borings performed. This will help the engineer compare the "good" soil area to the "bad" soil area.