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Undermined block foundation adjacent to fieldstone wall

Discussion in 'Residential Foundation Codes' started by PossibleMicrophone, Oct 2, 2019.

  1. PossibleMicrophone

    PossibleMicrophone Registered User

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    I'm working on a home, 1890s vintage, that has a fieldstone basement wall foundation with walls about 2' thick. The access to the basement is an adjoining fieldstone stairwell which was originally outside the house. An addition was built over the top of the basement entrance, and the walls of this addition were supported with a one-high cinder block wall with a poured concrete footer. Photo 1 shows this area from the outside.

    This cinder block wall is built up against the fieldstone wall of the basement entrance, though the former is far shallower. This section of cinder block wall has a gap in it where a concrete stair set was located, and has since been removed.

    The cinder block wall is being undermined by rainwater, which created a void that runs parallel to the wall and immediately below it. The void is about 1’ high x 1’ wide x 3’ long. The water is flowing through the void and then through a gap in the fieldstone of the basement. See Photo 2.

    What's concerning is that the void is not perpendicular to the wall. It runs almost the entire length of this short cinder block wall in the right side of Photo 1. At this point I have no idea what is holding up this cinder block wall; perhaps it's tied in to the concrete slab which was poured around the basement entrance, or part of the poured footer still has bite into the surrounding soil. Photo 3 shows more detail in this area.

    A proposal was to mudjack, since the undermined wall is holding up two floors above. However, since the void travels parallel to the fieldstone wall for the basement entrance, which doesn't bear any load from above, won’t the grout put pressure on the fieldstone wall, perhaps pushing it in? Is CLSM, or even expanding cement, a better option?
     
  2. Ty J.

    Ty J. Sawhorse

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    Wow, quite the interesting configuration of construction and development of a pending failure (give it time, maybe tomorrow or 10yrs, but this will fail).

    I'm sure many of us would like to help and provide some input, but in this case, the only comment that I can give is to hire a local engineer who can fully appreciate the existing construction and provide a complete design for the repairs.

    Best of luck!
     
    my250r11 likes this.
  3. Mark K

    Mark K Platinum Member

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    You need to hire an engineer to help understand the problem and to develop a solution. It is likely more complex than you think especially given what appears to be existence of adhoc construction. Your proposed solutions will not address the underlying problems.

    Any "solution" should address the source of the water. You need to divert the water or you will continue to have problems.
     
    my250r11 likes this.
  4. my250r11

    my250r11 Sawhorse

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    I agree with Ty & Mark.
     
  5. ADAguy

    ADAguy Sawhorse

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    Any idea as to soil condition, any adjacent water source other than rain?
     
  6. PossibleMicrophone

    PossibleMicrophone Registered User

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    Thanks for the replies everyone. The soil appears to be fairly low in clay content; via the USDA web soil survey it's classified as Galway loam. The water source is runoff from a rooftop where several surfaces flow into a valley...the flow rate can be 5-15 gallons per minute in heavy storms. It's important to fix that.
     
  7. ADAguy

    ADAguy Sawhorse

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    Oh, no gutters and downspouts! Definitely need to fix.
     

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