How to fix a loose timber retaining wall?

I have a small garden bed in my backyard. Recently I noticed that the timber retaining wall is coming off and needs to be secured. I have attached some photos for reference.

I would like to know if this is something I can fix myself or do I need professional help for this?

For a DIY fix, what products & tools do I need to use?

Thank you,

Husain

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JacobZ

Hi @husainZahid,

As the height of the retaining wall is low, it is very low risk, and it is certainly something you can do yourself.

The first thing you'll want to do is expose whatever the bolts are attached to, which is almost certainly a post that is currently concealed by the soil. I imagine if the sleepers are currently bowing out, then that post is likely rotten or its foundations have become compromised, in which case you would want to remove and replace that post, concreting it in to ensure it is nice and solid.

So, start by digging out behind the bolts to reveal the post. When the post is exposed, you can then dig it out using a fencing bar to break up the soil and a shovel to remove it. If there is concrete, then you can use a rotary hammer drill or jack hammer to break it up.

Once the post is out, you can install new ones. With retaining walls, they will often use a short length of a timber sleeper as a post, like shown in How To Build A Timber Retaining Wall. You'll want the post to go into the ground by around 500-600mm and then be encapsulated with 2-3 bags of post mix concrete per post.

Ensure you check for plumb and you push the sleepers back into place while the post can still be moved, then once dry, drill out new holes for the bolts and bolt the sleepers to the new post.

Let me know if you have any further questions.

Jacob

husainZahid

@JacobZ Thanks for your reply. The soil seems to have hardened a lot over time and not easy to dig out. Are there any specific tools or even machines (available for hire) that can help with digging the soil out? Would it be better to take all the soil out, fix the timber wall and then put the soil back in?

JacobZ

Hi @husainZahid,

You can hire a breaker (jackhammer), through our partners at Coates Hire. This will make light work of the hard soul and any concrete you might come across.

It would be worth removing some of the soil to relieve the pressure on the back of the sleepers before removing the posts. If you dug out a trench around 300mm wide and deep enough to see the bottom of that top row of sleepers, this will relieve the pressure and allow you to push everything back into place easier.

Let me know what you think and if you have further quetsions, please don't hesitate to ask.

Jacob

husainZahid

@JacobZ I have had a closer look at the retaining wall and dug up some soil behind it. It seems there is no post behind the timber retaining wall to support it. In fact the nails (yes, they're nails and not bolts) inserted into the timber wall do not come out through the other end. Not sure what was holding the timber wall so far. I have attached some more photos for reference.

MitchellMc

Hi @husainZahid,

That’s definitely unusual. Retaining wall sleepers don’t normally hold themselves in place without being fixed to a post behind them, so something structural is missing there.

It’s possible that there was a post originally and that it, along with the ends of the fixings, has completely disintegrated over time. That said, you would usually expect to find at least some trace of timber or metal, so it is odd that there’s nothing obvious remaining. Without a post, the sleepers would effectively have been relying on friction alone, which isn’t a proper or durable way to build a retaining wall.

The upside is that if there really is no post, it likely means there is no concrete footing for you to dig out either, which makes the repair easier. I would suggest continuing to excavate that spot and then installing a new post in the correct position, set into a concrete footing. Once the post is in and plumb, you can push the sleepers back into place and fix them properly to the post using bolts or suitable landscape screws rather than nails.

That should stabilise the wall and stop it from moving again.

Mitchell

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