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StructuralEng, Consultant
Category: Structural Engineering
Satisfied Customers: 7248
Experience:  Structural Engineer
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I have a house just built a couple of years ago. It is on a

Customer Question

I have a house just built a couple of years ago. It is on a pier and beam / block foundation with approximately a 42" high crawl space. The home was completed late summer/early fall. By January the following year we noticed movement in the center of the home downward by almost 2 inches. By summer that same year the house had returned to its original position. This process is repeated every year.I've had an engineer and an architect look at the problem and their conclusion was underground water and they suggested a curtain drain up the grade from the house. I believe that although that may not be a bad idea I believe that it is not the source of the problem as the ground is usually wetter in the winter and dryer in the summer and yet the house is sinking in the winter and rising in the summer.Any ideas as to what the cause may be and what the fix might be?Thank you,J Eiman
Submitted: 1 year ago.
Category: Structural Engineering
Expert:  StructuralEng replied 1 year ago.
Customer: replied 1 year ago.
What is this?
Expert:  StructuralEng replied 1 year ago.
What city and state are you in? Do you know the type of soil you have?
Customer: replied 1 year ago.
It is in the very NW corner of Arkansas. Rogers to be exact. The area is also know as the Ozarks with an elevation of 2,000' +/-. The soil is pretty much clay with a fair share of rocks. The footings and the piers were specifically dug to below the frost line for the area.
Expert:  StructuralEng replied 1 year ago.
If it's clay I would agree that this is an expansive soil issue. Obviously, I don't have the benefit of visiting your site, but this is fairly common with expansive soils and there is not much else (besides frost heave, which you said is not possible since the footings are below the frost line). Just because the ground is more wet in the winter, doesn't mean the soil is. The soil could be frozen and unable to absorb moisture and expand, then when it thaws it can absorb the moisture and expand.
Customer: replied 1 year ago.
I appreciate all that you have said but that doesn't cover my issue. If it was ground freezing then it would rise in the winter and settle in the summer. That scenario is 180 degrees from the situation I'm experiencing.Amy other ideas? Please keep in mind my house is sinking in the winter and rising in the summer.Thanks again,***@******.***
Expert:  StructuralEng replied 1 year ago.
I disagree. If the ground freezes in the winter, it won't raise the house. The footings are below frost so heave will not occur. What the freezing does is not allow the soil below he footing to absorb moisture and expand. AFTER the ground thaws it THEN absorbs the water and raises.
Additionally, I would ask on what you're basing the idea that the ground is more moist in winter? That's the reverse of what is typical and I wonder how you're arriving at that conclusion. It rains far more in the spring that in the fall. Clay has a notoriously low hydraulic conductivity and it take the moisture a long time to make its way several feet down through the clay t below the footings. This is why clay soils always fail percent tests...they do no drain.
Customer: replied 1 year ago.
Hi,I'm really not trying to be argumentative but the problem doesn't make sense for my particular situation. I have attached a couple of charts. The first of two things to note with the exception of 2016 be really wet our rain is fairly consistent year round. The second is the soil temperatures which never reach the freezing temp, especially this last winter where we saw the mildest conditions in years. Even with all the variations in the conditions the movement has been constant. Let me know what you think.Thank you!
Expert:  StructuralEng replied 1 year ago.
I still think you're looking at this as a "it rained most in winter, therefore the ground is the most wet in winter". That is just not a valid thought when it comes to a clay soil. It just isn't. Dig a hole in clay and fill it with water. Cover is so that evaporation does not occur and more water does not enter. It will take months to empty. There is no other phenomenon, beside frosting ground and expansive soils, that I've heard of that would make a footing raise and lower.
Customer: replied 1 year ago.
Okay, if what you say is correct, is the fix the curtain drain a couple of feet deeper than the piers or are deeper piers required?One more question, if this is the case then why isn't the entire house moving up and down as opposed to only the center which is resting on a pier (assuming the exterior footings are in the ground the same depth)?Thank you,