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retaining wall without proper drainage is leaning. solution

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  1. #1
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    Default retaining wall without proper drainage is leaning. solution

    I have a 8 foot retaining wall that was built without proper drainage. Its building up hydrostatic pressure whenever it rains, and the wall is leaning. I know the correct way to properly do this is dig all the way down and set up a french drain system and fill with river rocks all the way to the top. But early estimates are costing $25k to $30k. Someone suggested simply drilling some holes in the concrete wall to allow water to pass. Anyone tried this? does it get clogged with mud? does water really pass? Also how do i make sure i don't drill into and break the rebar and weakening the wall??

    i'm posting this in the other topics as well.

    thank you,

  2. #2
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    I've built many walls but this is a bit beyond my knowledge on how to "cheaply" rectify particularly when something this high goes bad.

    Whats it constructed out of? ie: is it block filled with concrete, concrete sleepers inserted into Steel H beams, Poured concrete using formwork, ...other

    I've seen big walls constructed with 90mm holes along the bottom every 2 to 4 meters but its likely to be in conjunction with free draining rock behind it and possibly slotted pipe.

    The big unknown is not only if the holes would be successful at eliminating or slowing down the problem but:
    - how many would be required
    - how big the holes would need to be to make a difference (or will it even make a difference) given it sounds like there is no good drainage behind the wall.
    - the footings are also a big unknown as you could go to all the trouble of fixing the drainage....even spending the 30k only to still see the wall lean further.

  3. #3
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    thank you for the input. appears to be cinder blocks filled with concrete? and rebar? I figure drilling would be worth a try? i can do myself at almost no cost. if i drill 1" holes every 2.5 feet, wondering if it would compromise the integrity of the wall? here are weep holes on the very bottom, but half of them don't appear to work anymore. When it rains, water drains out of half of them, but not the other half. And the other half is the leaning one.

  4. #4
    Golden Member havabeer's Avatar
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    yep this is something you're going to want an engineer to sign off on as thats a big wall.
    Remember if you don't sin, then Jesus died for nothing

  5. #5
    4K Club Member Marc's Avatar
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    If the wall is leaning a few degrees, and the center of gravity still falls within the footing area, the solution you deem expensive may work. Still no guarantee that the already compromised footings will stop sinking.
    If the leaning is more, taking the center of gravity outside the area of the footings, you will need to demolish, if you want to do it properly.
    Make sure you don't hire the same builder.
    Fear is the foundation of most government.
    John Adams

  6. #6
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    the wall leaning a bit, but contractors all seems to think it is strong enough to stay there. no need to demolish for now. Just need to release the hydrostatic pressure rain. before i pop down $30k to do a french drain. hoping someone would have some insight if i simply drill drain holes through the cinder block. and how do I avoid drilling through the rebar? or is it okay to drill through the center of the cinder block? i figure, if drilling doesn't
    work, I can still get the drainage done. Since i can drill it myself.

  7. #7
    4K Club Member Marc's Avatar
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    What kind of soil do you have on the other side? Clay or sand?
    If it is clay, the water will not flow out enough to make a difference, but you can always try.
    To avoid the reo, drill through the vertical mortar joint.
    Fear is the foundation of most government.
    John Adams

  8. #8
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    unfortunately, i think its clay like. hmm, sounds like a plan. to drill the vertical mortal holding the blocks together? to avoid rebar and weakening the structure?

  9. #9
    4K Club Member Marc's Avatar
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    You could start at the bottom row with a long masonry drill the size of the gap, say 3/8 or so, and clean out the joint top to bottom. The vertical joint dont have much structural value so it will not alter the strength of the wall.
    If you get water coming out even if slow, you are on a winner. Best of luck.
    Fear is the foundation of most government.
    John Adams

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