Child Item

How do I replace rotting retaining wall posts?

hoping for some advice.

I need to replace a rotting timber sleeper retaining wall and the new wall needs to follow the same line as the existing wall. Therefore my new posts will have to go in the same places as the old ones.

My concern is that the old posts are large (they are pieces of sleeper) and are set into a LOT of concrete, so digging them out will leave much bigger holes than the new galvanised posts will require.

What is the best approach to ensure the new posts are strong enough to support the new retaining wall? Do I just use heaps of concrete to fill the holes, or can I fill the old holes with soil, compact it as best as possible then re-dig more appropriate sized smaller holes to cement the new post into? Will the second option risk being too unstable due to being in disturbed earth?

Thanks for any advice about this!

The retaining wall is only 400mm high, and the earth behind it is very stable and not active in any way (it doesn’t get walked on of driven on).

Find more posts tagged with

Tools and Materials

Repairing

Landscaping

Comments

MitchellMc

Welcome to the Bunnings Workshop community @TandT. It's brilliant to have you join us, and many thanks for your question about installing retaining wall posts.

Would it be possible to offset the sleepers so the post hole location is in between the current posts? If you plan to use these H joiners for your posts, you must cut the sleeper in half for the mid-join. You'll need to start with a first length shorter than the others to offset the posts, but the installation should be straightforward.

You could dig out the current posts and concrete, backfill with soil and then compact it. You'd then be right to dig new holes suitable for your new smaller posts. That sounds like a heap of work, and I'd be trying to come up with any other solution than digging out the current posts.

Mitchell

Noyade

https://www.workshop.bunnings.com.au/discussion/comment/22886#Comment_22886

My two glasses of wine thought is to weld up brackets from steel plate and gal posts with a mounting plate that straddles the rotted hole left by the vertical sleepers. The new horizontal sleepers would be bolted forward of the drilled steel plates. Possibly it might look quite nice? Illustration wise I cannot compete with my good friend Mitchell.

*hic*

Never drink and Doodle

TandT

https://www.workshop.bunnings.com.au/discussion/comment/22886#Comment_22886

Thanks for this info Mitchell,

The offset idea could work for the intermediate posts. It'll still leave me with the corner posts (the wall has 2 corners) and 1 of the end posts that will absolutely have to go into existing holes. SO thank you also for the confirmation that it is okay to fill and compact the holes then re-dig smaller holes to cement the new posts. It's still a bit of work, but not as much as I was going to have to do!

My next question will be whether or not I can cut the composite sleepers I'm hoping to use. They're a Bunnings stock item (Fitta Composite Sleepers) They look to me as if they should be able to be cut with a metal cutting disc. Do you know if they can Mitchell? No worries if you don't because the Fitta Rep is apparently going to be at my local Bunnings this Friday so I can ask him or her then.

Thanks again

Tim

TandT

https://www.workshop.bunnings.com.au/discussion/comment/74110#Comment_74110

So wine is your creative thinking drink hey?

Works for me too, though scotch or beer are my more frequent choices.

Thanks for the creative idea....unfortunately I can't weld. Maybe when I dig down to the cement and find our exactly how big the mass is I'll decide it's time to learn and give your method a crack!

Thanks again

Tim

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/74116#Comment_74116

Hi @TandT,

My only concern with cutting the sleepers down would be that they have a plastic component. I'd imagine a metal cutting disc would go through them fine, but it could get a bit clogged. Did you have a link to the product you'd seen in stock? I can't find any currently on our website.

Mitchell

TandT

https://www.workshop.bunnings.com.au/discussion/comment/100583#Comment_100583

Hi again @MitchellMc

I don’t have a code, but there is a photo of the brochures of the 2 different products I’m considering.

The Fitta product on the left is my preference because it’s lighter so easier for me to work with as a DIY job, and I figure if I can cut it I’ll be able to cold galvanise the metal in it and re-seal the cut end of the sleeper to minimise rust issues in future.

the Ridgi product is concrete, so heavy and would be a nightmare to cut (plus I’m thinking cutting could compromise the reo bars I assume are in them and so would lead to cement cancer, ie rust and weakness over the decades that I want this wall to last).

very happy to hear your thoughts on any of this and REALLY appreciate your replies to date.

Thanks

Tim

Noyade

https://www.workshop.bunnings.com.au/discussion/comment/100583#Comment_100583

Afternoon @TandT

"Maybe when I dig down to the cement and find our exactly how big the mass is I'll decide it's time to learn and give your method a crack"

Yes, that's what I was thinking - trying to make use of your existing concrete. I made brackets outta scrap pipe and plate years ago that were bolted to an existing concrete edge surrounding a front garden. With concrete bolts there is immense holding power. Even some of the existing brackets at Bunnings may suffice - if there is enough concrete under the pebbles, seen above? But probably not if you're not going with treated sleepers again. I do think if you have crack at welding, you'll never look back as it opens up so many possibilities. Good luck with your project! 👍

Bolted to existing concrete edging.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/117164#Comment_117164

I believe they could be both special order products @TandT. I'd be happy to contact Fitta after the weekend to find out if you can cut their product.

Mitchell

TandT

https://www.workshop.bunnings.com.au/discussion/comment/126731#Comment_126731

Thanks @MitchellMc

that’d be great if you were able to find out for me.

Thanks for the offer.

Cheers

Tim

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/133105#Comment_133105

Hi Tim (@TandT),

The FITTA office is closed for the public holiday in QLD today. I'll give them a call tomorrow for you.

Thanks for your patience.

Mitchell

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/117165#Comment_117165

Hi @TandT,

You'll be pleased to know that it is super simple to cut Fitta SSR sleepers. Just pop a multi-material blade in a circular saw and it will cut right through them. You just need the multi-material blade to ensure it goes through the steel.

Sealing the cut end sounds like a cinch too. Spray the exposed steel (which is already galvanised), with some Cold Gal to seal the cut and you are good to go. If you want to ensure no water ingress to the end at all, you can use Sika 11FC and glue the cap they provide onto the end.

The Fitta sleepers sound like a fantastic solution that will suit your needs exactly.

Please let me know if you have further questions.

Mitchell

Dave-1

TandT

I was just looking at your retaining wall and was wondering if you could use something along these lines

https://www.bunnings.com.au/ridgi-50-x-50-x-3mm-1-2m-galvanised-steel-h-joiner-post-upright-sleeper_p1080308

If you could drive them vertically into the ground (use a saw to cut the slot in the reatining wall itself it may go someway to leave it insitu?

A jackhammer driving the post in may work? Ive never tried it myself but trying to think outside the square.

Dave

TandT

https://www.workshop.bunnings.com.au/discussion/comment/126734#Comment_126734

That is great news ! Thanks @MitchellMc

Looks like all I have to do now is clear a bit of space in the diary and get stuck in (may be a few weeks away but I'll post some photos when it's all underway!

TandT

https://www.workshop.bunnings.com.au/discussion/comment/22926#Comment_22926

Hi @Dave-1

Interesting thought...haha, I just tried to follow the link to the product but the Bunnings Web page is down for maintenance! I'll look again in the morning. I have to say I'm starting to feel pretty set on the full re-build with the Fitta sleepers, but I'll definitely check out your idea.

Thanks
Tim

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/74145#Comment_74145

@TandT

If you are thinking of a full rebuild then maybe Gabion baskets. Bunnings sells a few differant sizes and they work well (I have used them a fair bit) Just need stuff to fill the baskets. I have made some from scratch but ended up buying the premade ones for the corners. The Baskets are 400mm * 400mm * 800mm (If you go down the track I can give an idea on how to make them look level when you have a run of them.)

Dave Gabion wall build.jpg premade gabion wall.jpg Gabion wall Bunnings.jpg

TandT

https://www.workshop.bunnings.com.au/discussion/comment/100601#Comment_100601

Hi again @Dave-1

I really like the look of the gabion baskets, but they'd look too bulky for the relatively narrow garden this retaining wall is for.

Thanks for the suggestion though, I'm loving how this site brings out a variety of ideas, it's helping me make the best decision!

Cheers

Tim

EricL

https://www.workshop.bunnings.com.au/discussion/comment/117175#Comment_117175

Hi @TandT

Please keep us updated with your progress and if you run into any other issues while rebuilding your retaining wall, please let us know. I'm sure our members will be more than happy to provide you with advice and information.

Eric

TandT

https://www.workshop.bunnings.com.au/discussion/comment/126739#Comment_126739

We definitely will.

With other commitments already locked in, plus painting the house and digging some drainage before the worst of La Nina gets here, I think it'll be happening straight after Christmas. At least its all in the shade so the heat of summer won't be a deal breaker.

Child Item