Will retaining wall aluminium posts sink into concrete?

[spy1946]

Hi, planning to build a retaining wall 450mm high using the ridge brand of products the aluminium posts are 900mm in length, the instructions say to make sure the holes are 100mm deeper than the depth of your posts (450mm posts underground), my question is will these post sink after being inserted into the concrete (I’m not planning to use quick set concrete), or will they stay in place.

[MitchellMc · Accepted solution]

Welcome to the Bunnings Workshop community @spy1946. It's wonderful to have you join us, and many thanks for your question about setting posts in concrete.

Were these our Ridgi posts? If so, I do not see any aluminium options, but I can find the reference to the 100mm gap in their installation instructions. Regardless, anything you place in concrete will likely sink and needs to be supported, so it doesn't fall over.

The simplest solution would be duct-taping a couple of pieces of timber at a suitable height. This will stop the post from sinking and also keep it upright. In the landscaping industry, I think you'll likely find that a brick or bit of rubble would get thrown in the bottom of the hole to establish the 100mm gap.
 

Let me mention our landscaping specialist @Adam_W to get his thoughts.

Please let me know if you have any questions.

Mitchell