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Old 11-16-2009, 08:30 AM   #16
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the grading did not help and there is the strong possability the holes being so small they were not cleaned out properly thus the variations in settling. if twas me I would wait and see and maybe add more support to grade to spread the load. I still think a soil test is a must with proper calculations to give you real compression to bearing numbers, who would roll the dice on total collapse on a maybe
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Old 11-16-2009, 11:30 AM   #17
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It is clear that your piers are woefully undersized. You do not have the type of soil that could get by with such a small footprint (very few locations do).

The settling has nothing to do with the rain unless 1) the piers are on disturbed soil or 2) the clay is expansive and is actually lifting the outside piers so the inner piers appear to be settling. But given the extremely small footprint it seems obvious that the problem is too small of footprint.

Your building will continue to settle for it's lifetime unless you get proper footings under it. This is obviously over your builders head, if you let him proceed make sure you get a real engineer to size the right foundation and make sure the builder follows the engineers specs exactly.
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Old 11-16-2009, 05:22 PM   #18
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10,000 pounds per tube load bearing capacity

Hey all.

According to this flyer the footing tubes I have (8" diameter at top and 2' at base) can hold over 10,000 pounds per tube with a Till soil type (which I have). As such my building has 20 footing tubes and 6 10" sonotubes. The footing tubes alone should be able to carry over 215,000 pounds.

Is this correct. If so perhaps the settling was merely loose soil filling pockets under the abundant water that percolated down to the base of the footing due to poor landscape drainage on the job site.
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Old 11-16-2009, 06:57 PM   #19
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I am not clear how you know exactly what kind of soil you are on. You don't indicate that any soil testing was performed, so unless there is something you are not telling us, you are simply speculating that you are on till. Furthermore, till is a very non-specific term that simply means the soil is a heterogenous mixture of silt, clay, sand and gravel due to glacial mixing. A particular till can vary in strength from extremely strong (10,000 psf) to very weak (<2,000 psf) depending on the composition of the soil, and the relative density. These factors are normally established by a complete soil investigation prior to installing the foundation for a commercial building such as yours.

The fact that the piers have settled, some several inches, and the building is neither complete nor fully loaded, should suggest at a minimum that the soil is not adequate to support the load. Typical allowable settlement tolerance for footings is less than 1/4 inch in five feet, and that settlement should be immediate. Long term settlement such as you are encountering is by definition failure of the footing.

What puzzles me in this entire discussion is why the builder is not accepting responsibility for the foundation failure, or perhaps he is? It appears that the foundation was constructed with no soil investigation, and no professional design, therefore the builder must have assumed responsibility for the performance of the structure, unless your contract assigned responsibility to you. Rather than continue to speculate about the cause of the failure, and seek solutions in the absence of facts, you may want to discuss with your builder having them absorb the costs for a professional investigation, a redesign, and construction of an adequate foundation support system.

And as for the theory that water caused the failure, a competent foundation design in a moist area is based on the water table rising to the maximum probable level, therefore the foundation in your case should have been designed to perform adequately in saturated soil. Determination of the anticipated high groundwater level is standard procedure in any soil investigation, and if the footings are expected to be installed prior to adequate drainage being in place, the design should account for this fact.
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Old 11-17-2009, 08:50 AM   #20
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From looking at the pictures and reading the information on your project, the footings you have used are way too small and spaced to far apart. Due to these errors I would think that you are going to continue to have problems with sinking in the future. I have built several garages/barns using Bigfoot Systems Footing Forms.

Depending on the size/weight and soil conditions I have used either a 28 diameter Bigfoot Bell or a 36 diameter Bigfoot Bell. I have never had any issues with sinking. This could be a solution; their website; has load tables for the Bigfoot that will give the loads the footings can take in relation to the soil conditions.

Like others have stated you should have your soil tested and contact a structural engineer for any project of this size and magnitude. Hope this helps.
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