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Thread: OT: Need advice on foundation reconstruction / diagnosis

  1. #1
    Engineer chassis's Avatar
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    Default OT: Need advice on foundation reconstruction / diagnosis

    In-laws have a significantly cracked foundation. It's made of concrete blocks and was built about 1963-1965. It's in a lowish-area and is near a re-routed creek. The creek re-routing was done when the homes were built, early 1960s. The house is about 2200 s.f. and is a 2 story colonial, typical mid-60s construction in the midwest.

    I would like some references (websites or books) on:

    1. How to diagnose what caused the foundation to crack (fail).
    2. What are the options for repair and/or reconstruction?

    Thanks for any suggestions on where to conduct the research.

  2. #2
    In the Trades Bob NH's Avatar
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    House foundation failures can be caused by a lot of things including:
    1. Settling into bad soil
    2. Frost heaving due to inadequate depth below frost line
    3. Water pressure from the outside or under the foundation
    4. Weakening of the soil due to saturation
    5. Large tree roots applying pressure against the foundation wall
    6. External soil loads such as from a heavy load near the foundation
    7. Subsidance of the soil from pumping water or mining
    8. Changes in the supporting structure
    9. Inadeqaute design for the loads
    10. Changes in loads
    11. Nearby blasting
    12. Earthquakes
    13. Unknown unknowns
    14. Some that I haven't thought of

    http://www.askthebuilder.com/B10_For..._Footers.shtml

    You may send pictures. I have a high speed connection and accept EMail. Photos of the cracks with a ruler in the photos or other means to show dimensions, and photos of the house from all sides but especially on the sides corresponding to the location of the failures, would help to get you pointed in the right direction.

    Describe when the failures were first observed, and the time relative to any changes in the neighborhood or grading or modifications to the house.

    One quick way to fail a foundation wall is to bring a Ready-Mix concrete truck too close to the foundation.

  3. #3
    General Contractor Carpenter toolaholic's Avatar
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    Default i'm a s.f. gen contr.

    we do hill side foundations. every project starts with a soils eng.

    locate a ab chance cont. in your area.. a few helicals can be driven to refusal under the footer. then the found raised. very few folks now of this
    equept. and procedure. one side of my house was down over 3 inches,its level now. abchance co. it's owned by hubble co.

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    DIY Senior Member finnegan's Avatar
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    Cracks in foundations that appear significant do not always turn out to be that bad. If the foundation is crumbling, sagging or bulging, these are pretty much always bad. Are there signs of problems in the house above the foundation cracks such as cracked plaster/dywall? If you are concerned you might want to call in a mason to take a look or spring for an engineer.

  5. #5
    Engineer chassis's Avatar
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    Thanks for the input folks. Based on your suggestions, I also sat down with a book at Barnes & Noble last night, and it seems the cracks have to do with freeze/thaw or heaving. Probably because of an issue with drainage.

    The main crack is horizontal, and the full length of the "long" side of the foundation. It is bowing in toward the house, meaning the masonry joint is gaping open inside the house. The crack opening is about 3/8" in width. Halfway up from the slab floor/halfway down from the ground floor joists. This corresponds to the freeze line in SE Michigan, which is the location in question. I think the crack was first noticed about 3-5 yrs ago. Not sure how much it has grown or progressed, but my guess is that it has done so.

    In the middle of and adjacent foundation wall, there is a vertical crack from top to bottom in the foundation. On the second story there is vertical cracking in the plaster wall above a door jamb, which also happens to be almost the same place as the vertical crack in the foundation wall.

    I've discovered that for this particular piece of ground there is no FEMA floodplain map. I do know that a creek/small river was put underground before the homes in this area were built. My suspicion is that a drain tile/culvert containing the river has failed, saturating the ground near the foundation wall. The only way to prove this is to dig (I think??).

    It will be a complicated matter to resolve financially, if the munincipal tile has failed. The drain board for this particular creek is run by 2 counties and 3 local municipalities. Getting a resolution on this in my guesstimation will be time consuming and painful.

    What would be the most effective foundation repair? Assuming of course the drain commission fixes the culvert, if that is the problem.

    Thanks to all for your help on this, I appreciate the guidance and advice.

  6. #6
    In the Trades Bob NH's Avatar
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    Your description is consistent with poor drainage and freezing behind the wall.

    With the failure you already have, you should not accept any half measures to fix it.

    The fix will include removing the fill on the outside of the wall, installing drainage at the base of the wall, probably replace the wall, and backfill with good granular fill that will let water run down to your drainage system. If you aren't high enough for good drainage, then you should drain it somewhere to a sump and pump it out. The surface should be graded so it drains away from the house.

    It will not be possible to straighten the wall without removing the existing backfill. For a 3/8" gap as you described, the wall is probably bulging in an inch or more. Replacing the wall will require supporting the house while the old wall is removed.

    You will probably be spending some time reading the fine print in the EXCLUSIONS section of your homeowners policy.

  7. #7
    Engineer chassis's Avatar
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    Bob,

    Thanks alot. This is the in-laws house, and I am trying to do some background work to make their process a little less painful. They will come by the decision to correct the problem with great trepidation. When I speak to them on this I will ask them to get out the full text version of their homeowner's policy.

    Do you have any experience with foundation problems caused by failed municipal drainage tiles? I realize laws and localities make it hard to give a blanket statement. But have you seen a local town or township pay for a foundation reconstruction, if it was caused by a failed drain culvert?

  8. #8
    In the Trades Bob NH's Avatar
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    Default Towns Liable?

    I have been on the Planning Board and Board of Selectmen (governing body) where I live. Towns have "sovereign immunity" that limits their liability in a lot of areas, especially where it is a matter of judgement on decision processes. You would usually have to show that they were negligent, that they knew or should have known that the culvert had failed and neglected to fix it; or that the culvert was designed and installed with gross negligence.

    It is something like the "pothole rule". A city is liable for damage when you hit a pothole only if they have been previously notified of the pothole and had an opportunity to fix it.

    You would also have to show that the drainage failure was the cause of the wall failure, and not a failure of the builder to install appropriate backfill and foundation drainage. That may be difficult because if there was appropriate backfill and foundation drainage the failure of the culvert should not have made any difference.

    Most small towns are covered by insurance. Often, their insurance carrier will accept a settlement if the town is sued just to avoid a larger risk at trial. When I was on the Board of Selectmen a few years ago the "settle it" level was about $10,000 if the risk was close to $100,000.

  9. #9
    Engineer chassis's Avatar
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    Bob,

    Thanks again, you've helped immensely. It seems like the cost to repair the foundation will fall on my inlaws. Not a pleasant situation; I'm just trying to collect as many facts as possible so they can make an informed decision.

  10. #10
    General Contractor Carpenter toolaholic's Avatar
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    Default term for what u have

    the found. is rotating. call in a SOILS ENG. we can guess all day from miles away. eng. will look at the BIG picture.

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