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I'm working on creating a concrete retaining wall; which is between two large rocks; and will support a wall, and roof on top of it. The whole building is a 3m x 3m shed. When the retaining wall is complete (I'm building it in sections) it will be an area of 3m x 1.6m

Would the retaining wall benefit from expansion joints? If yes; how do I create an expansion joint? Would creating a grove in the concrete wall be enough? What size would the grove be; and should it run horizontal or vertical?

As there are rocks on either side; I imagine the concrete can only expand "up" - does this risk cracking the wall that it will start supporting?

The concrete is supporting earth on the "outside"; so its temperature will be relatively stable.

  • two rocks or two pieces of the same rock? should it be waterproof?
    – Jasen
    Dec 12, 2021 at 11:27
  • two rocks; I labeled them as stones in the picture. Yes; I will try to make it waterproof.
    – brent
    Dec 12, 2021 at 17:33
  • 1
    No, concrete shrinks, unless you have a very long wall and is subjected to huge temperature variations. 3m is not a length that would cause significant problems but surface cracks. How to properly "keyed" into the rock is the most important/challenging task
    – r13
    Dec 12, 2021 at 18:58
  • Sounds good; thanks - happy to accept that as the answer if you move it down?
    – brent
    Dec 17, 2021 at 9:52


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