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Thread: shoring up walls

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    Loco4Koi is offline
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    Question shoring up walls

    Besides concrete block,, what are people using to shore up walls... I'm digging a six foot deep pond... mostly clay and the bottom layers will likely be really hard caleche...
    looking to save money... is there a cheaper option than cinder block?

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    pressure treated plywood i have seen one build use this and they used tar on the earth side to extend the lifespan
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    I have also used treated plywood. Worked great and it also can be used for the inner form of a concrete collar.

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    My concern about treated plywood is it warping and bowing out as time goes by. Is that a legitimate concern or will the water pressure prevent that from happening

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    i would think that the pressure of the water will keep it from bowing.. you would want to make sure that the dirt walls are as straight up and down so prevent the plywood from bowing out of the pond.
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    So, what will happen when the plywood ages a bit and begins to rot AND the soil gets saturated from rain fall during the winter months? I can tell you from experience, saturated clay soils far outweigh the water pressure from inside a pond, especially from midlevel upward.

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    Loco4Koi is offline
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    Quote Originally Posted by koiman1950 View Post
    So, what will happen when the plywood ages a bit and begins to rot AND the soil gets saturated from rain fall during the winter months? I can tell you from experience, saturated clay soils far outweigh the water pressure from inside a pond, especially from midlevel upward.

    Mike
    Had one person tell me yo grease the plywood and it would last 20 years.underground, but my first thought was that grease would break down the liner..
    What about using hardy board... it's basically plywood made from concrete ...
    Have any of you used quickwall by quikrete? You basically plaster it on the outside of dry stacked concrete block... saw a youtube on it... I'm less than convinced of it's supposed strength.

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    Most pond projects are not 20 + year projects, and the treated plywood should last that long or more--even once it breaks down to pulp, then you're back to what you have now--just a rubber liner between a wall of water and a wall of dirt--that won't instantly disintegrate either.

    I like birdman's point about pouring a concrete collar around the top if you use plywood--that gives you a good flat base on which to put rock, and helps strengthen the wall at the weakest, least supported point--the very top, where water pressure holding against it is least, and the effects of a person stepping on it is the greatest.

    Compare the costs, though...I haven't, but I recall treated plywood being fairly high, and you'll need some structure to hold it firmly in place while you're putting backer and lining over it. Concrete blocks can possibly be found used, or in discount situations for not much more than a dollar per block (I'd only use the 8x8x16 blocks so the holes are big enough to fill with concrete). The cost of the concrete might be more significant, and the rebar too...again, some people have piles of rebar left over from other projects.

    I'd also worry about one stray splinter, protruding staple, or screw tip, and be quite wary of those possible liner threats. Either option will greatly improve just throwing the liner in the hole without any reinforcement, particularly being that deep.

    I haven't heard of anyone using hardiboard for a koi pond or in an underground application. I think it would come apart and get weak when wet, but maybe not.

    Was the quickwall supposed to give the dry stacked concrete blocks strength, or just be a way to apply a "finish coat" to them, and maybe keep the water from coming between them (remember, even if you fill the center holes with concrete, water can still move between the blocks).

    For strong and as permanent as you can get, I'd dry stack the concrete blocks....my opinion...or if there is a big price difference, use the plywood. Regarding it bowing, I'm assuming that the structure holding it would be on the dirt side of the plywood (maybe "studs" of treated 2x4's or 4x4's), and those would keep the plywood from bowing later on.

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    I would only use plywood in dry soils. In areas where the soil is always damp or wet I also would be concerned about it rotting. But all the plywood ponds I have done are holding up well.

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    Quote Originally Posted by Loco4Koi View Post
    ...Have any of you used quickwall by quikrete? You basically plaster it on the outside of dry stacked concrete block... saw a youtube on it... I'm less than convinced of it's supposed strength.
    I used it on my filter pit. It is indeed very strong, but not waterproof (like it says it is). Water "resistant", yes, but not proof.
    If I was using a liner, I might try it for support... although, with that said, I never have.
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    Last edited by icu2; 04-28-2012 at 10:57 AM.

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    I've decided to wrap the walls with 2"x4" welded wire... going to go with that spackled heavily with concrete ... I posted pics on my build thread ... on my tablet now, so can't post ... will let y'all know how it works out.... may go with plywood for my pit
    though ...
    I decided to go with wire instead of concrete block, which was my second choice. It'll give me cleaner lines with rounded corners.... definitely a work in progress; most of my decisions are being made on the fly to allow for creativity...

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