Using Concrete Blocks for a raised bed - unsafe?

Discussion in 'Edible Gardening' started by AndyS, Jan 15, 2018.

  1. AndyS

    AndyS Gardener

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    Hi,

    On our community allotment plot we have inherited some old concrete blocks - it's been suggested to use them for a raised bed but one person in our group is concerned that they can leach dangerous chemicals into the soil. Others seem to think it's nothing to worry about.

    Can anyone confirm if they are safe for food growing or not? There seems to be conflicting advice on various internet sites, and most of the info I can find is American, so I'm not sure if what they call 'cinder blocks' are made up in the same way as UK concrete blocks.

    Thanks,

    Andy
     
  2. JWK

    JWK Gardener Staff Member

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    If they are like the concrete blocks you can buy today in builders mechants, wickes etc then they are fine. They are just cement, sand and gravel - nothing harmful there.

    [​IMG]
     
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    • JWK

      JWK Gardener Staff Member

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      We call them breeze blocks.
       
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      • Scrungee

        Scrungee Well known for it

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          Last edited: Jan 15, 2018
        • misterQ

          misterQ Super Gardener

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          I would err on the side of caution and not use concrete blocks for edible crops.

          Chemical additives are some times used in the concrete mix to alter its working characteristics and it is these that I am most concerned about.
           
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          • NigelJ

            NigelJ Total Gardener

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            @AndyS If well weathered then most things will have leached out of them. Also if used in raised beds anything leaching out will tend to move down more than sideways and leaving a 6" gap will alleviate most problems. You could also line the inner side of the raised beds with split compost bags which would prevent contact with the blocks.
             
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            • pete

              pete Growing a bit of this and a bit of that....

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              Oh god, and I've got a concrete path:yikes:
              And it is in contact with the soil.:heehee:

              I'm still alive, well almost.:smile:
               
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              • ARMANDII

                ARMANDII Low Flying Administrator Staff Member

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                :dunno::whistle::heehee:
                 
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                • Scrungee

                  Scrungee Well known for it

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                  Others might have concrete blockwork used in their house/garage foundations, but if so, I don't think it's a good idea to dig deep trenches down to the bottom of the concrete footings all around your property and line your foundations with old plastic compost bags.

                  [​IMG]
                   
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                    Last edited: Jan 27, 2018
                  • wiseowl

                    wiseowl FRIENDLY ADMIN Staff Member

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                    Good morning I have 3 large raised beds made with breeze blocks and have never had any problems with them:smile:

                    3 the same as this one
                    [​IMG]
                     
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                    • noisette47

                      noisette47 Total Gardener

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                      I'd have thought that the only problems that might arise are if you want to grow ericaceous-loving plants in them...e.g. blackcurrants, blueberries. Shouldn't be a problem with brassicas as they prefer a bit of lime in the soil. If the blocks have old mortar residues, they could alter the ph of the soil a bit, but as NigelJ says, lining the inside of the beds with plastic sacks would stop leaching. What the plastic leaches into the soil is another story :scratch: If you do go down that route, keep an eye open for colonies of snails...they love hollow spaces to lurk in!
                       
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                      • shiney

                        shiney President, Grumpy Old Men's Club Staff Member

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                        As you say they are old concrete blocks then you won't have any problem. :dbgrtmb:
                         
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                        • Scrungee

                          Scrungee Well known for it

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                          Googling will find as many reports of plastic toxins as it will find reports about concrete blockwork toxins :yikes:

                          Plastic flower pots, seeds trays, compost bags, etc. are all supposed to leach toxins and contaminate your soil/plants as none of them are food safe. Non foodsafe hosepipes should not be used according to some reports. Follow their advice and you'd only grow stuff in plastic coffee cups and margarine/icecream tubs.

                          And as Sunflowers are supposed to take contaminants from the soil, when growing in suspect ground should they have their flowers removed to prevent poisoning of bees and birds, then be binned rather than composted?
                           
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                            Last edited: Jan 16, 2018
                          • noisette47

                            noisette47 Total Gardener

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                          • shiney

                            shiney President, Grumpy Old Men's Club Staff Member

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                            Don't forget not to breathe the air as it's full of contaminants! :hate-shocked:

                            Life was much better in my younger days when we only had to worry about things such as the black plague, consumption, dropsy, leprosy, miasma, rickets, scurvy etc. :phew: :snorky:
                             
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