What to put between drainage layer and soil?

Discussion in 'Designing, building, making and powering your life' started by petal, May 22, 2008.

  1. petal

    petal Junior Member

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    We have new retaining wall about 80 to 100 cm high. It is made of red gum sleepers and ‘H’ beams. Behind the wall is 20-30cm wide strip of scoria with the slotted agi pipe at the bottom. We would like put a layer of soil on top of the scoria and plant up to the wall.

    What is recommended to stop the soil falling into the scoria? I am tossing up between shade cloth and a layer of 14mm gravel. The shade cloth would be quick and easy, but may break down and create a mess of fibers in the soil. The gravel would be lots more work and cost. Is it worth the extra effort and cost of the gravel, or is the shade cloth a good long term solution?

    Is there a better way?

    Also how deep would the soil need to be, to be useful in growing small perennials?
     
  2. IntensiveGardener

    IntensiveGardener Junior Member

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    Re: What to put between drainage layer and soil?

    I'v encountered a similar problem while repairing a drain. I'v been considering using a metal based flyscreen material instead of the shade cloth. I havn't tryed it yet but it seems a lot tougher.

    The soil should be 25-30cms deep minimum. The deeper the better really. 60cms is heaps.
     
  3. gardenlen

    gardenlen Group for banned users

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    Re: What to put between drainage layer and soil?

    g'day petal.

    we used old shade cloth doubled (old fly screen should also do the job) though i don't reckon it needs to be, check the drawings of how we did an ag' drain on our site, once the pipe is laid thn i would come up at least 1/3 the height of the wall using only cracked stone nothing else and with the shade cloth before the soil, not sure how metal fly screen will go unless it is copper, shade cloth is pretty much perpetual.

    len
     
  4. ppp

    ppp Junior Member

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    Re: What to put between drainage layer and soil?

    you wouldn't need a thick layer of gravel. If your layers are consistent, probably 100mm would be fine.
    14mm gravel still has quite large pores in it. Would you consider a thin layer of coarse sand / fine gravel / crusher dust on top?
     
  5. petal

    petal Junior Member

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    Re: What to put between drainage layer and soil?

    Thanks Len, IntensiveGardener, and ppp. I have decided to go with shade cloth because the scoria is already in place, almost to the top of the wall. Yesterday I found out how hard it is to dig/scrape it out, so the less I need to remove the better. I also found some old shade cloth in the backyard. Your are right Len, it looks like new and won’t breakdown for ages. I like the idea of a layer of course sand/fine gravel and will try that if we put in another drain.
     

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