How to build a U-shaped retaining wall?

Hello there. I am planning retaining wall in my backyard, having slope of approx 600mm from the lowest point to the desired height of Alfresco Floor.

The retaining wall will be U shaped 13.2m x 4.8m x4.8

=> Question is H4 sleepers along with timber stumps are suitable for this project

I should use the concrete sleepers here with galvanised posts?

(The ground will be levelled afterwards assuming the wall should be sturdy to withhold 8-10 cubic meter of soil)

I want longevity but when it comes to using the concrete sleepers It wont be easy to tapper the sleepers ☹️

Looking forward for the valuable feedback

Find more posts tagged with

Tools and Materials

Gardening

Building and Construction

Landscaping

Comments

JacobZ

Hi @Mo2,

Thank you for your question about installing a retaining wall structure in your backyard.

While retaining walls under 1m in height don't typically require council approval, due to the large size and volume of soil being retained, I'd suggest it is worthwhile reaching out to your local council for advice before deciding on a method. It is worth a quick phone call to ensure your plans are in line with what they require.

If longevity is key, which it certainly should be, I'd suggest using reinforced concrete sleepers, such as those from Ridgi alongside the corresponding galvanised posts. This is for a few simple reasons, the concrete won't rot or bend, galvanised steel doesn't rust if the galvanisation is kept intact, and they are stronger materials than timber.

There is no need to taper the sleepers, and I would advise against it regardless of whether you use timber or concrete. It's a bit of manual labour, but it is much easier to just dig out a trench for the sleeper to sit in. Once everything is backfilled, you'll never know.

The next thing to consider is drainage. This is because any water within the soil will add to the weight pressing on the wall. This is known as hydrostatic pressure. You'll want to ensure drainage gravel and agi pipe are installed along the back edge of the retaining wall, particularly at the bottom of the slope. If you have a stormwater outlet in your yard, the agi pipe should be connected to it by a plumber.

Allow me to tag @Nailbag and @Dave-1 to see if they have any helpful advice.

It looks like a great project and I'm excited to hear your thoughts on the above.

Jacob

Dave-1

Afternoon @Mo2

That area will look pretty nice 🙂

I will throw in a gabion retaining wall instead of a timber or concrete one 🙂 The Gabion wall allows water through it and is very easy to build. You can also buy pre made baskets from Bunnings

They come in a range of sizes but are also very easy to make them yourself. Check out my bookmarks if you would like to see some examples 🙂

Timber retaining wall, prob the next Id choose, digging holes for the posts, if you are going with 600mm high then 1200mm deep is what Id be thinking. Also having the spacing no further then say 1200mm appart will give the life of your wall the longest chance. Drainage is something you will need to factor in.

Concrete sleepers will last the longest, tho drainage would really have to be configured into it.

One thing that you may want to consider is teh height of the level area compared to your fence, you may end up having to factor in some privacy screen of some kind. Id suggest to mark on your fence how high the new area will be, then grab a ladder and stand at that height 🙂 A step down from your patio could be worthwhile as well as not needing so many resources?

Dave

Nailbag

Hi @Mo2

The only thing I can add to both @JacobZ and @Dave-1 advice would be to line the inside of the wall with builders plastic. This will prevent any water/dirt seeping through the layers of sleepers.

Nailbag

Mo2

https://www.workshop.bunnings.com.au/discussion/comment/46901#Comment_46901

Hello again.

I am about to pour concrete for galvanised posts. The post I am using is 1200mm with 600mm will be inside the ground.

Question here is it okay to do the dry pouring of quick mix concrete OR wet pouring is necessary.

I find dry pouring easier but not sure if there is any difference in terms of the strength.

Another Question is can I lay the stones (pic attached) at the base of posts ?

Regards

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/86462#Comment_86462

Hi @Mo2,

You can add gravel under and at the base of the post, which will assist with drainage.

There will be directions on the concrete as to how it should be used. If you are using Australian Builders 20kg Quick Set Concrete, you would fill the hole partially full with water and then pour the dry mix on top of it. There's a video on the product page which shows how to do this.

Provided you follow the directions on the packaging, dry pouring will be adequate strength-wise.

Please let me know if you have any questions.

Mitchell

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/108606#Comment_108606

Afternoon @Mo2

When I have used drypouring with the quickset concrete for my windbreak posts the water wicked away so fast I either had too much or not enough and the concrete itself was dissapearing into the soil 😕

I have had no issue of mixing the concrete in a wheelbarrow and then pouring it into the hole. I actually found it way less stressful doing that way. Just dont drop you bag of concrete into a plastic wheelbarrow 😕 I did and "crack" lol

Gravel as @MitchellMc has said will enable drainage so why not.

Dave

Nailbag

https://www.workshop.bunnings.com.au/discussion/comment/86462#Comment_86462

Hi @Mo2

I actually just replaced 2 fence posts yesterday using Australian Builders 20kg Quick Set Concrete, The process is exactly as @MitchellMc mentioned, which is to add the water first, then the concrete. Mix this in with your shovel or in my case a long star-picket. The process is repeated for each bag you add. The most important part of the process is ensuring your mixing the water and concrete by scooping some up as you go which also checks for areas of dry concrete.

Nailbag

Child Item