How to fix a rotting timber retaining wall?

We have this timber retaining wall that’s aprox 8 years old that is starting to rot, we are hoping we can do something to stop it in its tracks like cement rendering it etc. we are about to tile the concrete and have our pergola area screened in and the screen will be up reasonably close to the wall.

any suggestions of being able to fix this without having to remove the timber would be appreciated .

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Comments

EricL

Hello @shenmon

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about fixing your retaining wall.

It looks like your retaining wall has been painted with a clear sealer. If it has, it will need to be removed in order to apply the timber preservative products I'll be recommending. Another issue that comes to mind is that water has passed inside the timber sleeper and caused unseen damage inside the sleeper. I propose testing the rotted portions with a screwdriver and pressing hard on the black sections of the sleeper. If the screwdriver sinks deep and the timber falls apart, then its highly probable that the sleeper is very much damaged and will need to be replaced.

To help preserve your aging timber retaining wall without replacing it, there are a few approaches you can try to slow down the rot and protect it. One option is to apply a timber preservative like Bondall’s Timber Protect, this product penetrates the wood to protect against further decay and can be applied with a brush, focusing on areas that show signs of rot. Just make sure to clean off any dirt or debris before applying.

If you want a more substantial barrier, consider waterproofing the wall with a bitumen-based sealer, like Crommelin’s Black shield. This type of sealer is often used on retaining walls and can provide a water-resistant barrier to protect the timber from further moisture exposure. Applying a few coats on the exposed timber could help prolong its lifespan.

Please keep in mind that this is on the condition that the sleeper is still in good condition and is structurally sound.

Finally, make sure the area around the retaining wall has good drainage to prevent further moisture buildup. Since you’re planning to screen in the pergola area, ensure there’s adequate airflow around the wall, as this will help reduce trapped moisture and slow down the rot.

Let me call on our experienced members @Dave-1 and @Nailbag for their recommendations.

If you have any other questions we can help with, please let us know.

Eric

Dave-1

Good Morning @shenmon

Mmmmm this is a hard call, I was trying to think of a solution around the issue but not really happy with my idea.

How many posts have the issue btw? And also which way does the water flow on the concrete and pool?

I will put it down in case you want to use it interm wise but I would not suggest long term due to the stresses involved on the retaining side.

First suggestion, only if the posts are rotted through substantially really.

I would suggest that you install these brackets every 1/4 along the length of the sleepers.

Bolting via concrete screws into the ground and then screwed into short posts that match the height of your wall.

I would do the second 1/4 and third 1/4 first then remove the joining rotted post (sawing it off at the concrete level) and then installing the first 1/4 and so on. I am concerened about the Soil wanting to push over the wall (even tho its only low, long term it will travel)

Second suggestion

Considering what you want to do to the area and the effort you are going to expend on it I would be tempted to remove the posts/rails and redo. if one post is rotted, there is a fair chance the others will be as well. Replacing the retaining wall same for same should be resonably easy just lots of work. I would suggest if you do then you factor in drainage (grill drain) at the edge of the concrete slab as that is potentially the cause of the issue 😕

I do like @EricL 's idea and have the same hesitation because of the coating of the timber. It looks like a beautiful lawn and a nice retaining wall for your area so better to factor in preventative install then try and prolong an issue. It would be interesting to see which way you go as I am sure the other members will have ideas aslo 🙂 Ive taken several suggestions and thrown them all in the bucket and then picked out some that might work when Ive been in the same type of choice.

Definently a good one for a "Welcome to the Bunnings community" 🙂

Dave

Nailbag

Hi @shenmon

I think both @EricL and @Dave-1 have provided some great advice in their comments.

My concern is that the bottom of the posts appear to be effected, which are all that are supporting the sleepers which are rotting at the ends. So, if you can reasonably easy push a screwdriver in this spots especially the bottom of the posts, then I would be inclined rebuild the wall. Especially if you intend to stay at the home for some considerable time and the last thing you want to do is pull up any of the new sections your building.

If you weren't shortly doing the new pergola works, then I would be seriously considering the steps of long term "temporary" repair. But its still not going to be anywhere near as longer lasting as replacement, especially @EricL has noted there is a high chance there is sections rotting behind or deep within what's currently good sections you can't see or have access to check.

Another thought to give a better understanding of the sleepers condition is to dig a few open holes on the backside where I suspect you will find evidence of a lot more rotted wood.

Regards, Nailbag

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