How do I replace rotting retaining wall posts?

[TandT]

Hi

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).

[MitchellMc]

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 · Accepted solution]

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_...

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]

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]

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]

@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

[TandT]

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]

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]

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.