# Forum Home Renovation Retaining Walls  Strengthening an existing Timber Retaining Wall?

## ed612313

Hello,
Ive just moved into our 1st home and we have an old wooden retaining wall that id like to strengthen up as it sits beside our kids playing area and has "fallen apart" somewhat.
Its approx 1m high and 7m long.
I was thinking of just whacking in a few steel flat bars into the soil ie a 2m flat bar and sledge it 1m deep leaving 1m out of the ground to add additional support. Hoping to get a few ideas on here as to wether that's the way to go about it or what other options are available?
Thanks
Ed

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## Marc

That wall is a nice winter project, knock down and rebuild.
Meantime you can add new posts to it to prevent it from falling. Flat bar will do bugger all. 
If the wall had been still vertical, you could make a permanent fix with new post tied up at the top to an anchor in the ground behind. The way it is, short of dismantling the section that is leaning, dig the soil behind it and rebuild, there is no way to push it back in line. 
If you intend to rebuild properly, you can tie up the existing post to a cross member under ground, and wait for when you are ready to rebuild.

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## ed612313

Hi Marc, thanks for getting bak to me.   

> Meantime you can add new posts to it to prevent it from falling.

   - Given the wall is 1m high what length would the posts need to be? And how far would I need to drive them into the ground? Would I need to add concrete? Dig and jack hammer or hire a post driver from kennards? 
If you intend to rebuild properly, you can tie up the existing post to a cross member under ground, and wait for when you are ready to rebuild - Sounds like this will eventually have to happen. Any links or details on how this would be done? Sorry - Im a complete amateur with retaining walls and I kind of get what you are saying but not sure how I would do it? 
Thanks for the response. Appreciated
Ed

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## BIM

Search Deadman retaining wall anchors here https://www.google.com/search?q=dead...A_enAU801AU801
BTW you will require posts back and front  pretension the cable ties a distance 3 x wall height
hth

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## Bros

Firstly it is not going to collapse it will just slowly move out. 
You can use a ground anchor which is what we did with a friends retaining wall but it was much higher. 
Obviously it is made on the cheap so as Marc said rebuild and do it to this standard post No4 https://www.renovateforum.com/f82/re...advice-129234/

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## r3nov8or

The design in Bros's linked post (leaning into the retained area) could be done without removing the current wall, if yo6u happy to lose a little more lower space for a little more upper garden. Remove the first and/or second course of old timber and chop the old posts lower, backfill with gravel, and add new top soil - if the soil dug for the new holes is good, use it above. All done. You can take your time. Less mess and you don't need to dispose of (all of) the old timber

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## Marc

> Hi Marc, thanks for getting back to me. 
>  - Given the wall is 1m high what length would the posts need to be? And how far would I need to drive them into the ground? Would I need to add concrete? Dig and jack hammer or hire a post driver from kennards? 
> Thanks for the response. Appreciated
> Ed

  http://www.ozbuildmaterials.com.au/p...ications03.pdf 
The link above, gives a bit more information about the mechanics at play in a retaining wall. 
Considering I don't know the soil structure, water flow, existence or lack of drainage and other details, I would never claim that a retaining wall is safe and will not fail. Much less looking at those photos. Sure, it may stay like that for another 10 years. Or not.  
Patch up or rebuild? Depends on money and energy available. You can do a decent patch up and keep this going for a while. Rebuild with the same style, or rebuild with dedicated retaining wall blocks that will outlive your grandchildren.  
If, like it seems, you want to just stabilise the wall temporarily forever ... or for a while  :Smilie:  ... each of the above suggestions have merit. To your question, the short answer is .08m however ... depth of post is not the only consideration. A post that withstands lateral forces relies on it's strength (diameter and soft or hardwood) and the type of soil. Soft and wet soil will allow the post to travel sideways. A thin post will cut through the soil easier than a thick one. Concrete will increase the diameter of the post and give it more surface to push against ... etc 
An easy hack to increase a post lateral strength is anchoring the top with a SS cable rein or chain, tied to a section of same post, laying inside a trench a few meters behind the wall. A 600 mm sleeper placed horizontal with the wide side towards the wall will keep the post from leaning for a long time. The same piece of sleeper buried at the base of the post, just below ground level will have similar effect, but will rely on the post strength more than the rein at the top of the post.  
Your first consideration is ... how will you fit new post vertical against a collapsing wall? You either remove the section that is out of plumb, fit new post and rebuild, or you place the new post out of line and rebuild following this new position. I don't like either, but it is your choice. Perhaps trying to keep the existing line with new vertical post, is the most conservative way to patch this up. 
If it is me, I would pull the lot down and build a proper wall with Keystones. May be even making the wall undulating ... but that is my taste ...  :Smilie:  
As for how to dig the holes ... working against a 1m high wall and needing to dig the holes right against the wall is not easy. Using a hand post hole digger or an auger, you will in both cases need to take part of the wall down to have room to move. Not to mention if you have rocks in the ground to make the job more interesting  :Smilie: 
Let us know how you go and take many pictures

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