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How to build a retaining wall with 3m sleepers?

Hi all,

I am working on a small area in my yard (3.2m x 3.8m) to install a stepped retaining wall to level out surfaces at both levels. Refer to the pictures below. I plan to use the retain-it metal posts to hold in the 3 x (50mm x 150mm) timber sleepers making the wall 450mm high, the pieces are 3m in length.

1. Are 50mm thick sleepers too thin to hold back the soil? should I go to 75mm?

2. Should I be cutting the 3m lengths into two 1.5m lengths and have a middle post, concerned the 3m sleepers with no middle post may bow over time? I will install an ag line to drain water buildup in front of the retaining wall to the open area as I don't have a connection to stormwater for this small area.

Thank You

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Comments

JacobZ

Hi @Yangaz,

Thank you for your question about using 3-metre sleepers to build a retaining wall.

There is certainly some potential that 3m sleepers can bow over time and you might like to consider going the extra mile now when the work is still being done to prevent this from happening.

The ag line will certainly help to mitigate this issue as the most weight the sleepers will need to hold back will occur when the soil becomes sodden. Adding this drainage will move the water away from the retaining wall and lessen the load applied to the retaining wall.

Moving to a 75mm sleeper, or even a hardwood sleeper will lower the potential for bowing over time, but as it appears like you've already purchased your sleepers, I'd suggest cutting the sleepers you have to 1.5m and adding the mid-post.

It is very unlikely that the sleepers will bow over 1.5m so this would be the most cost-effective way for you to ensure a nice straight retaining wall for years to come.

Let me know if you have any further questions.

Jacob

Yangaz

Thanks Jacob, so is using 50mm thick sleepers 450mm high (3 pieces) okay?

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/39728#Comment_39728

Hi @Yangaz,

There are no worries at all assuming the posts are well anchored with at least 2 bags of concrete each.

Let me know if you've got any other questions.

Jacob

Yangaz

https://www.workshop.bunnings.com.au/discussion/comment/82051#Comment_82051

Thanks, what would you do for the short end of the area? i.e. 1.4m where it slopes down slightly? any good ideas?

EricL

https://www.workshop.bunnings.com.au/discussion/comment/105775#Comment_105775

Hello @Yangaz

If one side of the retaining wall is lower than the other side, my best advice is to make sure to compensate for the low area. Just keep in mind that the top part of the retaining wall must be all at the same level.

That could possibly mean that you'll need to use a longer post, or the soil area will need to be adjusted in order for the wall to be uniform.

If you need further assistance, please let us know.

Eric

Yangaz

https://www.workshop.bunnings.com.au/discussion/comment/120047#Comment_120047

Thank you,

Regarding drainage, I intend to install an ag line using some spare 100mm socked slotted draincoil which I can use on the front of the retaining wall. I've read that some use a fabric blanket before pouring blue metal to avoid dirt and debris getting into the ag line. Given the ag-line has a sock already is this fabric still required?

Regards

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/128771#Comment_128771

Hi @Yangaz,

The geotextile membrane is more to keep the soil from getting in between the stone which will limit the water's ability to flow freely between the stones and find its way into the ag line.

It is not 100% necessary but is a fairly simple way to prevent unnecessary maintenance.

I would suggest it is worth the relatively small expense to save yourself a lot of work in the future.

Let me know if you have any further questions.

Jacob

Yangaz

https://www.workshop.bunnings.com.au/discussion/comment/134313#Comment_134313

Thanks, Jacob,

Here is the progress shot below. Please see the area circled in red. Unfortunately, I cannot connect this back into an existing drainage point but will distribute the water from the retaining wall into a larger area. Do I still need to tie the fabric ends of the slotted black pipe?

Also, what would you recommend for a good surface where the dirt is? I was considering 40mm blue metal but maybe something more aesthetically pleasing?

Thank You

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/137866#Comment_137866

Hi @Yangaz,

It's coming along nicely, thank you for sharing the update.

You might find that the soil erodes a bit where you discharge the ag line, so a good amount of drainage gravel at the end is a must. Also, make sure the ag line falls towards the end you want it to discharge, otherwise it will just sit in the ag line and not drain away as intended.

You should definitely tie the sock over the ends, this will allow water to pass through the sock but will stop dirt and debris getting in.

I actually like the look of blue metal, but that may just be me. There are certainly other options you could use, maybe something like these Iceberg Decorative Stones or Black Decorative Pebble Mix will work for you.

Let me know what you think and if you have any further questions.

Jacob

Yangaz

https://www.workshop.bunnings.com.au/discussion/comment/140272#Comment_140272

Thanks, Jacob for the quick response. I think we will go for the Iceberg decorative stones, is there anything I should put on top of the dirt to avoid grass and weed and also loose dirt?

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/142005#Comment_142005

Hi @Yangaz,

You can lay some weed control mat down and secure it in place with weed mat pins before covering the area with your decorative stones.

This will help keep the dirt in place and act as a barrier to prevent the weeds growing through.

Let me know if you have any other questions.

Jacob

Yangaz

https://www.workshop.bunnings.com.au/discussion/comment/143265#Comment_143265

Hi,

Here is the latest update.

The bottom level has been completed using the ki-carma iceberg stones, which turned out to be a nice warm colour to offset the grey-rendered walls of the house.

Now, working on the top layer. We decided to also put the same stones on the top level of the area. Can I use coarse sand to level the surface before applying a weed mat and then the stones on top? something like this? https://www.bunnings.com.au/ki-carma-20kg-coarse-landscape-sand_p3460054?srsltid=AfmBOoptFUEwR97cQ9yDj19bAmUjykSLxmSAxRVe0r10506pgub0iGz2

Would you recommend putting in another timber sleeper on the top level where I've placed the sleeper in the picture so that the dirt and rocks don't run off?

https://www.bunnings.com.au/ki-carma-20kg-16-25mm-iceberg-decorative-stones_p3460044

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/144222#Comment_144222

Hi @Yangaz,

It looks like things are coming along nicely. Thank you for the update.

If you're planning to level and place more stones in the top area, I would definitely add another timber sleeper across the front to keep the stones in place. Ideally, you would have this sleeper run level with your other retaining wall, so some digging will be required.

The other thing I notice is that your sleeper posts sit slightly above the top sleeper. Was there a reason for this, or was it a slight oversight?

If you wanted to cut them so they sit flush with the top of your sleepers, you could use an angle grinder with some cut off discs to cut them flush with the top of the sleepers. If you were to do this, please ensure you wear gloves, eye protection, hearing protection, long work clothes and a mask.

Let me know what you think and if you have any further questions or updates, please don't hesitate to post them.

Jacob

Yangaz

https://www.workshop.bunnings.com.au/discussion/comment/144902#Comment_144902

Hey @JacobZ

Here is a more recent photo. Yes, I did find the posts being higher quite annoying so I replaced the top tier sleeper with a wider 200mm sleeper to fit nicely.

In regards to the top-level surface, can I use ki-carma coarse sand to act as a leveling surface before I put down the weed mat and then the rocks on top?

Would you also use posts for the timber sleeper for the front to keep the stones in place?

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/145435#Comment_145435

Hi @Yangaz,

That looks even better, congratulations on the progress.

Yes, that would be a great way to level the area before adding weed mat and stones.

For the single layer sleeper, I would add a Jack 75 x 450mm End Post concreted in at either end of the opening for the sleepers to sit in. This will give you a good strong barrier that will keep everything in place.

Please keep us updated with your progress, I'm very excited to see the finished product.

Jacob

Yangaz

https://www.workshop.bunnings.com.au/discussion/comment/145849#Comment_145849

Just checking back in guys, finally finished the job! See below before and after pics. Thanks for your help again! onto the next project.

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/146168#Comment_146168

Hi @Yangaz,

Thanks for the update, it looks like you had a busy weekend finishing this up.

You truly have done a brilliant job and I'm sure it will be even better once some plants are in your planter and everything has had time to settle in.

Thank you for sharing this project with us, I'm excited to see the next one.

Jacob

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