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Timber groynes installation..

Hi there,

Would you please advise me on the method for installation of oak timber sleepers vertically into the ground? I've been advised to put them in the ground by 300mm and postcrete them in. They will be free-standing with approximately 500mm between each one.

Thanks very much for your help!

Best wishes


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  • I think you'll need to give a few more details................ how tall are they going to be? Are they going to be holding something... back like soil? What sort of soil are you putting them in? So many questions!!

  • PRO

    This may help (I can't take credit for schematic as it was sent to me when we had a similar/retaining wall  requirement).

    Just make sure specify the correct UC grade sleepers (not just go for the cheapest) otherwise they will fail at ground level within 5-7yrs max. Select from a supplier that will guarantee their use.

    • I think it's worth pointing out that all the timber guarantees (that I know of) covers only the timber, not the much larger cost of breaking out and reinstalling! We use nothing but UC4 posts and they don't last much more than 8 years in the above scenario in sandy soils.

      Judi has done the right thing in my book by going for oak sleepers. Creosoted will last even longer, but not suitable for many project due to bleeding.

  • if they are free standing and 500mm apart i cant see they will be holding anything back, but the height will affect the depth, dependent on what you are trying to achieve

  • Thanks so much for your responses. What I'm doing is creating a small beach garden, there is no retaining element to the design. Drawing attached. Obviously, I want them to last as long as possible in the ground. The upright sleepers are representing sea groynes. And I want to put large square bolts through them, hopefully to get rusty in time and all aged to look more interesting.. The design has evolved since this initial sketch. We are now putting in curved pathways to summerhouse and beach area. I'm having the groynes at different heights: 2 x 1000mm, 2 x 800mm & 2 x 600mm.

    • Really nice sketch! The only thing is- the sleepers appear way fatter in that drawing than they will in real life. Oak sleepers are only 200mm wide. You may need a couple extra to achieve the same effect.

      You won't have to wait long for the bolts to go rusty in oak! Spray them with a bit of salty water too.

      I'd put the sleepers at least 600mm in the ground looking at that. If the ground is at all loose or gets wet 300mm will have them leaning over in no time, regardless of concrete.

      • Hi Ben,

        Many thanks for your reply! Good advice about putting two uprights together.. I really like that idea!

        Best wishes


        • Hi Ben, this is how the garden turned out in reality. Next is the planting and summerhouse in the top right-hand corner next to the beach feel garden. Do you see the upright timber groynes.. love it and so do my clients. Thanks so much for your advice! :-)


    • PRO

      A little tip.

      To kickstart aging of bolts, pop them in a bbq for an hour (especially if they are galvanised). 


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