How to replace a wooden retaining wall?

[sthornber]

Hi,

1st time on Bunnings workshop. 
Looking for advice….
Looking at removing old rotten wooden retaining wall, and to replace it with concrete sleepers, over 24 metres long. 
I was thinking of keeping the existing posts. Only thing is they all vary, from each other, some are 2,400mm to 1,600. 
Do I cut off the existing post and drill new holes for the posts at 2 metres apart, so a 2 metre sleeper can slide straight in?
Considering this is over 24 metres, do I do this section by section?

Happy to listen to all ideas/thoughts

[Akanksha]

Welcome to the Bunnings Workshop community, @sthornber. Great to see you make your first post. Trust you've been finding the site a useful resource containing handy advice and inspiring ideas for your home improvement and garden projects.

Thanks for your question on replacing your wooden retaining wall. Our resident Bunnings D.I.Y. expert @EricL will be online later today and will be happy to assist you.

Let me tag @julzdiy, @Baggs, @Dave-1, @TedBear and @Jimi for their thoughts in the meantime.

Akanksha

[TedBear]

Hi @sthornber, in my experience, trying to work the old in with the new is usually more trouble than it's worth. I suggest that you do remove the old posts as they will likely be a source of frustration and get in the way. I'd be placing the new ones, one at a time as you go, so that any small errors in placement don't become large errors toward the end, especially with such a long length. It would be extra work to have to relocate supports after they are already in place.

[Professional installers might do them all first, but their experience would inform them of how much allowance to make for differences in sleeper length.]

[Dave-1]

Good morning @sthornber 

Id like to say welcome to the crowd The Bunnings workshop community is a pretty interesting place to take a stroll through. There will always be one of us that has had a similar issue or can offer some helping words. Downfall  of wandering through and looking at the projects is you will get sidetracked!

I agree with @TedBear  for sure in not reusing the old posts (wall) in this instance (I am a big believer in reuse however) You mention concrete sleepers, I am pretty sure they are use dwith Galvinised posts that you slot them into? Could you tell us what type you are considering?

Id mark out the whole retaining wall in the location you want while factoring in garden bed width, whats behind the existing wall, drainage.Id mark it out using a stringline. Then I would go along and put it in stages as 24m will take some time (well for me it would )

I have watched a neighbour down the street from my place put this style of retaining wall in and he took at least 6 months without an issue. 

The only concern I have is when you remove the old wall either in sections or wholly how far down to those fence support posts go?

Dave

[sthornber]

  

Thank you all for your feedback. A few more images to look at. It looks like it will be a big job for me but willing to give it a go. The cement sleepers will be 2,000 length x 200 height x 80 width

With the fence posts supports, I’m not sure how down they run. Will only know that when I start the job. It’s good point though. 

[Dave-1]

Evening @sthornber 

You must be superman! lol Man those sleepers will be on the heavy side! Now that I can see the fence posts you have me thinking of replacing the actual timber rails with tiimber, They are U chanels so could stay in situ and you cut the new timber to length? Unless you are set on the concrete style. Whichever way I would also suggest to put in drainage at the bottom of the retianing wall, It will help prolong the new wall.

Would love to see a pic of the project as it unfolds btw. 

Dave

[sthornber]

Evening Dave-1

No superman here 😄. I may have a friend to lift the concrete sleepers into position. 
I’m thinking of doing this, section by section and removing the old posts and installing new ones 2 metres apart. 
My next question, what is the best tool to dig/drill 800mm in depth and what diameter?

Considering I don’t have much room for machinery down the side of the house
Thank you

[Dave-1]

Good morning @sthornber 

You and your mate may feel like superman after that workout! 

Post holes, especially if you are going to be doing section by section I would use a square mouthed shovel cyclone square mouth post hole shovel 

Make a square the width of the blade using the blade and work your way down. All my posts that I have put in I used this process. My posts are usually around the 650mm mark and that shovel rocks I Actually came across a picture of my shovel (from building my deck) from a decade ago and its still rocking today

You can hire a mechanical post digger but if you are going to do section by section that may cost a bit. (Never used one before)

Always keep in mind that something may be where you want to dig, waterpipe (Oh yeah I have hit a few lol) sewage pipe (yep did that once when I was a pre-apprentice) or stormwater, let alone power/internet/phone. 

Dave

[EricL]

Hello @sthornber 

It's great that you've received excellent advice from our members. It's a challenging undertaking, but if you do it one section at a time, you'll be able to approximate how long the project will take. Looking at the pictures you posted it seems that the brick flooring was placed after the retaining wall. 

It will be necessary to factor in the disassembly of the brick floor to your jobs list. My best advice is to call either your local council or Before You Dig to make sure there are no local services running under the new spot where you'll be putting your posts in.

Please keep us updated with your progress, we look forward to the start of your retaining wall project.

Eric

[sthornber]

Thank you all for your input. I certainly have a lot to think about. This information has been very helpful and I feel I have enough to go to giving this job a go