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Allotment - new raised beds... some advice.

I've posted a couple of times that we have taken over an allotment this year. 
We have much of it now under control and some of the existing beds in use. 

In the middle of the plot there was a large area with nothing panted and covered in some weeds and grass. We started to clear this last weekend and quickly discovered that there's a huge concrete slab a couple of inches underneath the grass/loose soil covering. I'm guessing the greenhouse on the plot was moved at some point (or there were two originally). The concrete is cracked in places and has a lot of weeds coming through with pretty serious roots going on. 

Rather than breaking up the concrete I'm thinking of covering the limited soil with a weed control membrane, then placing some new raised beds over the membrane. 

I've managed to source some pallet collars which stack nicely for creating small beds (120xm x 80cm). 
I'm thinking of putting some of these in doubled up in height (so 40cm tall) and some triples (60 cm height) and filling with a mix of bark and stones at the bottom for drainage and compost (have more of this around than top soil). 

Any flaws in this plan I've not considered? (still making this up as I go along really)

Thanks :)
Steve

Posts

  • AmphibiosAmphibios LondonshirePosts: 158
    Hi Steve, 

    I had similar questions recently but unfortunately my post got lost in the traffic. What I gleaned from old posts was: 
    - @josusa47 has built raised beds on concrete. She did not break up the concrete before hand. Her post did not say what drainage she had. 
    - line your planters with plastic if you would like them to last longer. Any plastic showing above the soil will degrade in the sun. 
    - best drainage is gravel but I can’t find the post with the size of gravel and amount needed. I had lots of rubble that I used in a layer. 
    - compost scarcity - I didn’t have much compost and my raised bed is huge. I used the lasagna method And layered cardboard and green plant waste to bulk up the bottom. 
    - I used this thread to figure out the combinations of compost/topsoil etc. 


    - when filled, water the bed and leave it to settle a week or 2, apparently the volume will go down. I’m at this stage now and luckily writing this post reminded me to wait a bit before planting! 

    Good luck with your raised beds 

    A x 
  • stevek_bathstevek_bath Posts: 51
    Amphibios said:
    Hi Steve, 

    I had similar questions recently but unfortunately my post got lost in the traffic. What I gleaned from old posts was: 
    - @josusa47 has built raised beds on concrete. She did not break up the concrete before hand. Her post did not say what drainage she had. 
    - line your planters with plastic if you would like them to last longer. Any plastic showing above the soil will degrade in the sun. 
    - best drainage is gravel but I can’t find the post with the size of gravel and amount needed. I had lots of rubble that I used in a layer. 
    - compost scarcity - I didn’t have much compost and my raised bed is huge. I used the lasagna method And layered cardboard and green plant waste to bulk up the bottom. 
    - I used this thread to figure out the combinations of compost/topsoil etc. 


    - when filled, water the bed and leave it to settle a week or 2, apparently the volume will go down. I’m at this stage now and luckily writing this post reminded me to wait a bit before planting! 

    Good luck with your raised beds 

    A x 
    That's so helpful thank you!
    Now just need to find some topsoil. Thanks again. 
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