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How to replace a timber retaining wall?

Hello All,

First ever post on the Bunnings DIY workshop site. Have recently moved into this first home for us in Australia 🙂 and found this retaining wall in backyard which is quite old (20+ years) and rotten. Thinking about replacing it with new timber from Bunnings. Questions:

how do I remove it considering the concrete on front side and second any other ideas to do something else with this? It’s about 8m in length

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MitchellMc

Welcome to the Bunnings Workshop community @shariqullahkhan. It's fabulous that you've joined us, and many thanks for the question about restoring your retaining wall.

First off, congratulations on purchasing your home. I trust it's an extremely exciting time for you!

Your wall looks very aged, but I'm not seeing a lot of rot. I can see that there is a little on the left of one of the treads on the step section. I can't quite tell, but is there rot at the bottom of the vertical posts where they enter the concrete? That will be a concern if there is. The reason for mentioning this is apart from the large cracks is that the wall could be quite sound. You could paint it to disguise the issues or apply a pigmented oil to restore some colour if it is.

Alternatively, if the wall is sound, my preference would be to use the walls structure and clad over it. Is this retaining wall at the back door and, if so, have you considered building a deck at all? This wall could be incorporated into it. Using SpecRite 1800 x 902mm Pre-Oiled Merbau Alternating Slat Fence Panel would be an easy way to clad the wall. I'd suggest placing them horizontally and cutting them to suit the height of the retaining wall. They can then be fixed to the front face. You could fix Ironwood 200 x 50mm 2.4m Sienna Treated Pine Sleepers over the existing sleepers for the top.

If the wall can't be saved, you can dismantle it and replace it all with new timber. Replacing the upright post will be a little troublesome, and you'll likely need to cut the concrete slab back to cement in new posts. It's just a matter of starting from the top and taking it apart piece by piece.

Let me mention one of our experienced members, @Adam_W, to see if he has any thoughts.

Please let me know if you have any questions.

Mitchell

Adam_W

Hi @shariqullahkhan & welcome!
I think it's safe to assume that the concrete was lain after the wall and that's what creates the problem for you. You could probably carefully remove the old wall but you wouldn't be able to concrete in new posts.
It's a bit of a conundrum as the concrete itself has seen better days and that cracking etc. will only get worse.

Okay... so two options as I see it.
1) - Get someone in to use a wet-saw concrete cutter to cut a neat line around 200mm out from the face of the uprights all the way along and then remove that concrete. I can't see a neat, safe way that you could just cut out around the posts unfortunately.

If you have experience with a large concrete wet-saw you could DIY but they are very aggressive, unforgiving & specialist tools.

Once cut then you can remove that strip of concrete and the wall before replacing the wall and then re-concreting if desired.

2) - Although a larger project this would be my preferred option... Remove the concrete as it will likely need replacement in the next few years anyway, remove & replace the wall and then either re-concrete or pave the area.

shariqullahkhan

Thanks @MitchellMc and @Adam_W for the reply and suggestions..

i have added some more pics of the wall from the side. It’s actually falling on the front. Probably when it was installed they didn’t put drainage behind and that could be the reason. I tried pushing one the posts using a hammer, ref pic to straighten it but it’s not gone back even a millimetre. The pressure of the ground from the back on the wall has also put some cracks on concrete as you have already noticed. I like the idea of using a wet-saw. My neighbour is a concrete guy and I can ask his help to cut it in straight line.
I’ve added some more pictures of the backyard, it’s a slope from back to front and left to right. That’s why I wanted to put a new one and increase the height of the retaining wall to fill in soil to decrease the incline as much as I can. Sorry I’m asking too many things probably in one post but that’s the difficulty here… not sure where to start.

Decking the pergola is already in my plan but it probably need to wait few months due to my tight financial situation.

What would be your suggestion (in terms of steps) to uplift this backyard.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/16412#Comment_16412

That wall has had its day, @shariqullahkhan. Thanks for the additional images.

As opposed to cutting the concrete, why not remove the wall and cut the posts off. You could chisel and drill out the top of them and fill the void with cement. Your new posts can be set back off the concrete slab, allowing you to set them in concrete. You'll lose the thickness of the post from the yard, but it might be worth it to avoid dealing with the slab.

Remember that the wall might have been kept this low, as any higher would require an engineer. Check with your local or state authority on maximum allowable non-engineered retaining wall height. If you're trying to keep to a budget, it might be worth working within the permissible height.

Mitchell

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