How to repair this rotting timber retaining wall?

@j3mesf1

The easiest method to replace a retaining wall is to build another directly in front, while the soil behind remains retained. Walls that have been built with just a 5deg backwards angle will provide more strength and less chance of tilting forward over time.

75 x 2400 treated pine sleepers will also be stronger than the existing 50mm thick ones.using Galvanised posts will also be a stronger construction over vertical sleepers, though add considerable cost.

The new wall should be double layer lined with black plastic stapled along the top. Once built you can remove the original top wall cap and first row of sleepers and back fill the gap.

Since the garden edge suffers from water pooling, I would recommend an Ag pipe drainage system under the surface along the garden edge and connected to the storm water to prevent the pooling.

All of the above can be done by a landscaper should the project be overwhelming, as it would be a decent project.

Nailbag

Screenshot 2024-08-06 at 10.31.00 PM.png

Good Morning @j3mesf1

Well I am actually going to suggest option 3, the one that you may not be so keen on. That is to replace teh sleepers that have rotted (And check the rest of the low sleepers in that bed) Your Garden bed looks solid with no bowing other then that rotted piece. A bit of maintenece may save headaches further down the track.

The amount of effort you will have to go to to either install a new frame in front of a temporary fix may as well be put towards teh repair of the bed. The uprights are ok for now so if you leave tehm then the potyential that the rot will spread is high.

The palms you have in the bed are clumping roots and should be able to stand up to the boards being removed without too much strain on them. If you do go down the route of replacing sections of the bed (I actually think it will be the easiest but then I like digging 🙂 ) I would install drainage at the bottom of the bed against the wall and also have somewhere excess water can actually drain to.

Dave

Thanks everyone, this place is a gold mine for excellent feedback and advice I really appreciate it.

@Dave-1 I feel your idea is the one I will humour first as it's going to the least expensive option and one I can get a feel for without having to go all in. My main unknown is if it has been correctly backfilled with gravel originally if that will pour out and make the replacement process an issue.

If I can remove a run at a time and drop in replacements then it's a big win.

Unfortunately there's not enough room to build another wall in front of this existing one (the pathway of the wall runs along a narrow path further behind the images) so I do need a solution which keeps the wall where it currently is.

Once again much appreciate the help, I will post back with how I go to perhaps help others in future as well from any of my lessons learned the hard way...

https://www.workshop.bunnings.com.au/discussion/comment/40603#Comment_40603

Morning @j3mesf1

Feel your concern over the fill pouring out, think of it as an excuse to revitalize the bed? Id start collecting a bunch of containers (Pool Chlorine sized ones) to put the "fill" in so you dont end up with a pile of dirt/gravel as you replace the sleepers. I have a pool and have over a dozen buckets I have kept and keep using to shift and store soil 🙂 Ask around your neighbours if you dont have one and you could be lucky. (The plastic dosnt become brittle with time and they are very hardy plus come with a lid)

Will wait for the project 🙂 I think its a good one as so many of us end up with your quandry.

Dave

https://www.workshop.bunnings.com.au/discussion/comment/82461#Comment_82461

Thanks Dave. I was going to just put a tarp down under the wall and handle it that way. My fingers are crossed there's a layer of gravel in behind which will pour out and give me ample working space to make the task easier.

Tomorrow I will have a go.

EricL

https://www.workshop.bunnings.com.au/discussion/comment/105997#Comment_105997

Hi @j3mesf1

Please keep us updated with your progress, we look forward to seeing your retaining wall repaired.

Eric

https://www.workshop.bunnings.com.au/discussion/comment/105997#Comment_105997

Hi @j3mesf1 @it’s not normal practice to backfill a retaining wall with gravel. It should be back lined with plastic and then normal soil. But it often might be a mixture of anything at the lower parts just to cheaply fill the void.

Your most likely going to find very compressed soil behind so hopefully not to much will spill out. This should make replacement of each sleeper easier.

Personally I would still be positioning the ag drainage along the garden line not the sleeper wall. The idea is to prevent water reaching the wall and your garden. It’s been the excess pooling water that’s contributing to the sleeper rot.

Nailbag

https://www.workshop.bunnings.com.au/discussion/comment/120156#Comment_120156

Timely post Nailbag, I just finished having a look. Managed to get the top row off and as you say only found densely packed soil and roots behind which held its shape. No plastic lining however.

My issue is it's now apparent they screwed all the sleepers in from the back into the uprights so i can just crowbar them up and out. I guess it leaves me with cutting them all down the middle and prying them out which compromises the job massively. Not sure what the next best step is.

https://www.workshop.bunnings.com.au/discussion/comment/128843#Comment_128843

Morning @j3mesf1

Remove all the soil from the segmant all the way through to the other side, it will save effort overall by just trying to remove what you need to to get a tool in there. The screws may be rusted so another option is to use a metal cutting tool and cut the screw between the post and the rail.

Ozito PXC 18V Cordless Multi Function Tool PXMFTS-018 - Skin Only

Dave

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/128843#Comment_128843

Another option @j3mesf1, is a reciprocating saw with a long metal cutting blade.

You'll need to lever out the sleeper out just enough to slip the blade between it and the post.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/134352#Comment_134352

Yep have thought of that and ordered a long multi tool blade to try and get in.

I'm quietly optimistic if I can deal with the screws it'll be a manageable task.

Thanks all

https://www.workshop.bunnings.com.au/discussion/comment/137894#Comment_137894

Hi @j3mesf1 just checking it’s a reciprocating blade you’re getting not a “multitool” one? You will chew through them even using the best hard metal cutting blades through them at great expense.

The blade @MitchellMc recommended will go though wood and hard metals countless times and a great all-rounder blade to have. Where possible Just mix up where on the blade teeth are doing the work so not to put all the wear on just them.

When cutting just nails and large screws I tend to use dedicated metal cutting blades as they are thinner, faster and have more flexibility to make flusher cuts. The screws are most likely 8ga gal batten ones common in retaining walls. So you will need the power and blade type to cut them.

The other benefit of using a recip saw is that you can get pruning blades that might come in handy to trim back any roots pushing up against any of the sleepers

Nailbag

https://www.workshop.bunnings.com.au/discussion/comment/140293#Comment_140293

Thanks @Nailbag

Yes sorry I used the wrong terminology there. I'll use the reciprocating saw which should be fine as I can use the space gained by removing the sleeper above it in each row to gain access to them. The point about the roots is really good too and will for sure be helpful.

https://www.workshop.bunnings.com.au/discussion/comment/142024#Comment_142024

Glad to hear it @j3mesf1 and you will find that pruning blade also a very safe accessory for pruning tree branches as well.

One last point regarding the replacement sleepers. The existing ones have smooth faces and beveled edges. So, it’s possible they are Ironwood and not the everyday treated pine which have rough faces and no bevel. It’s also a reddish colour to distinguish the difference as they are also Arsenic-free. @MitchellMc or @EricL will be able to advise availability.

If there is a supply issue, and you own a planer, you could create your own be bevel to standard treated pine sleepers. Otherwise a random orbit sander would do an amicable job, the bevels just won’t be as sharply defined.

Looking forward to a few updated photos.

Nailbag.

https://www.workshop.bunnings.com.au/discussion/comment/44744#Comment_44744

Hi again,

Thought I'd update with progress. I've successfully replaced the sleepers in this section after some challenges along the way.

Initially I was hoping to only replace the bottom sleeper but it became evident very quickly that all would need replacing as you'll see in the images.

The combination of roots and moisture made short work of each sleeper but the silver lining was that scrapping them made disassembly a lot easier. I was able to saw down each side to pull them out then using a reciprocating saw, shear the bolts holding the ends in to pull them out.

The largest challenge I faced was that the soil had deformed the sleepers and it was bowed so heavily I had to grade two wheel barrows worth of soil to make it square again for the incoming sleepers. Very painful!

Once done I repacked the agg pipe at the botto with gravel and placed plastic over the top. I hope a combination of this and the heavy painting will help combat future rot better.

Thanks again for the advice, certainly made the process easier.

Only 8 sections remaining....

JacobZ

Hi @j3mesf1,

It's brilliant to see you've made some progress. Hopefully, your experience from this first section makes the rest a little bit easier to manage.

I note that @Terry66 is currently dealing with a similar issue and could certainly benefit from seeing what you've done.

Thank you for sharing.

Jacob

https://www.workshop.bunnings.com.au/discussion/comment/84491#Comment_84491

Evening @j3mesf1

Nice work in repairing the wall 🙂 Worth the effort and now you know its good for another bunch of years 🙂

Dave