How to Install A Concrete Sleeper Retaining Wall

If you’re starting to tackle more contracting projects on your own or have gotten into functional landscaping, concrete sleeper retaining walls are a great feature to learn how to install given how much they can add to a landscape. However, these walls are also one of the more challenging tasks in building functional gardens.

Although they do take some preparation and cost planning, retaining walls can also offer a range of benefits to your home and property – especially if your land is on a slope. When a whole slope is backfilled against a retaining wall, it’s extra important to ensure your retaining wall is both built with supportive materials like concrete, and that it’s constructed correctly to support the integrity of your land. 

Want to know how to install a concrete sleeper retaining wall the right way? Read along, or watch the video below, to learn how to install a concrete sleeper retaining wall with our experienced team at Outback Fencing.

 

Why Install Concrete Sleeper Retaining Walls?

Retaining walls work as a way to turn a slope or two sections of land into a platform with two different levels. Concrete sleepers, specifically, have been used in railway lines and construction projects for many years – since the Victorian era! – because they’re sturdy and meet the right strength requirements.

For garden spaces, concrete sleeper retaining walls are perfect when landscaping on a hill or slope. Retaining walls are also ideal for creating levels in an outdoor space, bringing character and sectionality – like a higher level to design with garden plants and a lower entertaining area with something like composite decking.

How to Install A Concrete Sleeper Retaining Wall

Below we’ll list the materials you’ll need to construct your concrete sleeper retaining wall. Make sure you have all these supplies on-hand before then following our step-by-step guide on how to correctly install your concrete sleeper retaining wall.

• Plan and Prepare the Site
• Dig Post Holes
• Set the Posts
• Create a Concrete Pad for the Sleepers to Sit On
• Install the Concrete Sleepers
• Install a Wedge between the Sleepers
• Waterproof and Drainage Preparation

Materials Needed:

• Concrete sleepers
• Steel posts
• String lines
• Laser level or standard level
• Timber wedges (sacrificial timber is fine)
• Builder’s film (black plastic)
• AG pipe
• Aggregate (stone or gravel)
• Tools (shovel, post driver, hammer, concrete mixer)

Step-By-Step Guide for Retaining Wall Installation

1. Plan and Prepare the Site

First of all, you’ll need to prepare the site and determine where you want the wall to go. Steer away from other features of your property and keep at least a 1.5m gap between things like pool fencing, the house itself or your privacy fencing. Follow these two steps for the planning stage:

• Mark the wall location by using pegs or string lines to outline where your retaining wall will go, making sure that it aligns with your boundary and fills the space at the right height.

• Check the height of the planned fence by using a string line or level to confirm the wall will be at the correct height for the backyard area. Adjust the height of the string lines to match the required height of the wall.

2. Dig Post Holes

With the site prepared and the wall dimensions planned out with string lines, you can begin work by digging the post holes.

• Dig holes approximately 400-450mm wide and 600-700mm deep. This ensures they are large enough to accommodate the posts and hold the concrete that will secure them.

• To space the holes correctly, mark out the hole positions to align with the spans of your concrete sleepers. You can lay a concrete sleeper out and measure its length, then use the distance between that for the centre of your holes.

3. Set the Posts

With the holes created to the correct depth, width and spacing, it’s time to place the posts in position and knock them into the ground to set the posts.

• Positioning posts into place once the holes are ready. As you do this, use a string line or laser level to ensure they are straight and at the correct height.

• Level the posts by checking if they align to the string line. You might need to adjust the post's position so that it’s level using a spirit level.

• Knock the posts into place by firming and pushing the posts down with your hands until you can't push them down much further. Then switch to hitting the post down with a sledgehammer, using a piece of sacrificial timber on top to protect the post.

4. Create a Concrete Pad for the Sleepers to Sit On

As sleeper walls are usually 600mm high, we need to create a concrete pad for the sleepers to sit on. The top of the pad will need to come up to 600mm below the top of the post.

• Measure 600mm from the base to the required level where the sleeper will sit. Create a smooth concrete pad to support the sleeper along the wall.

• Ensure the concrete pads are smooth and allow for proper positioning of the sleepers, ensuring they remain level.

5. Install the Concrete Sleepers

The posts are the foundations for your sleeper wall, and once they’re installed, you can go ahead and install the sleepers.

• Install the first sleeper on each set of posts. Do this by carefully placing the concrete sleeper between the posts. Ideally, there should be around a 10mm gap between the sleeper and the post for smooth installation. Use a level to ensure the first concrete sleeper is installed straight.

• Install the remaining sleepers by repeating the process for each consecutive sleeper, adjusting for any gaps using timber wedges if necessary.

6. Install a Wedge between the Sleepers

As you will have a small gap between the concrete sleepers and the sides of the steel posts, you’ll need to add some timber in this gap to keep the concrete snug.

• Cut some timber wedges around the size of the gap between the back of the concrete sleepers and the posts.

• Use a hammer to hit the wedge into the gap. These wedges are to hold the sleepers in place until the wall is backfilled, at which time the back-filling material will do the job of holding the concrete sleepers in place. 

7. Waterproof and Drainage Preparation

Proper retaining walls that help work as they’re meant to and can boost the value of your property are not complete without water protection and drainage features.

• Once the wall is in place, install builder's film (black plastic) behind the wall to prevent moisture from passing through and affecting the sleepers.

• Lay an AG pipe behind the wall to help direct water away. This will ensure proper drainage and prevent water buildup behind the wall.

• Cover the AG pipe with aggregate (stone or gravel) to encourage proper water flow and to keep the area behind the wall dry.

Install an Optimal Concrete Sleeper Retaining Wall for your Home & Garden

Depending on the function of your feature wall, it’s likely you or someone will backfill it with soil from the land next to or above it. While this step is an entirely different task and needs to be done carefully, with the pointers in this article and in the video above, you’ll have all the information you need to create your concrete sleeper retaining wall.

From here, there is plenty of possibility for the homeowner to create two sections for whatever they like. For example, many retaining walls are used to create an upper level with anAustralian native garden design, and a lower one with pavement and some planter boxes. Others use it to separate the pool from an entertaining area. 

Retaining walls are a hidden gem when it comes to practical design tips. By following these steps, you'll have a secure, durable concrete sleeper retaining wall that enhances the look and functionality of your space.

If you have any questions, would like more information or are wondering where to get your products and materials from, contact us to find out more.