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By sonny |
    • Place a string line on the retaining wall site.


    • Use a post-hole digger with a 250mm or 300mm drill to dig the beginning and end post holes. To gauge the depth and provide maximum strength, approximately half the vertical post should protrude from the ground.


    • If you are building a retaining wall over 1 meter high, the vertical posts need to “lean” slightly backwards. The diameter of the hole should leave a minimum of 75mm for the concrete to surround the log for its entire depth.


    • Dig middle post holes (minimum 1500mm spacing) to the same depth and angle. If you know you will need to use more than one log per width, plan your middle posts to the length of your logs so that the join looks seamless.


    • Put a shovel full of blue metal or gravel of some kind into the bottom to prevent water from building up.


    • Put the post into the ground and pack wet or dry pre-mix concrete around it. Add water if dry, and use a spirit level, plumb-bob and a brace to ensure the upright post stays at the right angle and vertical.


    • After about 24 hours, when the concrete has set and starting from the bottom, attach the logs or half logs to the retaining wall side of the vertical posts. If you are using half round logs, the rounded part should face outwards. Use 10mm galvanised nails for this task and keep using your spirit level to ensure they lie flat. (Please note that your concrete will take 30 days to fully cure.)


    • Place some gravel or blue metal on the very bottom behind the logs, and invest in some Ag pipe (Agricultural piping) to help disperse excess water. Make sure that the pipe leads towards an approved stormwater drain and does not flow into yours or someone else’s property. You may need to consult a plumber/drainage specialist about this.


    • You may choose to line the log wall with plastic if you are building in sandy soil.


  • Backfill the retaining wall with gravel or blue metal to cover the ag pipe, and then fill the rest with the appropriate soil for what you wish to grow or place on top.