How to build a retaining wall

Retaining Wall

How to build a retaining wall

Building a retaining wall is a great way to enhance how your garden looks, add value and protect your vegetable garden or flower bed. And with the right materials, it’s easier than you may think.

Some things to take into consideration when planning to build a retaining wall are:

  • Are there buried utility lines near or adjacent to where you want to build the wall? If so, you may have to find a different location. If you’re unsure, dial before you dig.
  • Will you need a building permit from your local government authority / council? If the retaining wall exceeds a certain height, the answer is likely yes. The only way to know for sure is to contact your local council to see what the city planning department requires. Get approval to build.
  • Will the type of soil in your garden cause issues with the retaining wall? Keep in mind that clay soils hold moisture, which puts more pressure on a wall when compared to sandy soils. Organic soils should never be used to build a wall because although the soil will stick together, it will not hold.
  • Make sure you have the ability to build on solid ground. If the area you want to build the wall has soft wet soil, the soil may need to be replaced with a better base material and firmly compacted.

Retaining Wall Supplies

For this project’s construction materials, you’ll need quick-set concrete (about one bag per hole), 100mm bugle head screws, and most importantly, 200 x 50 x 2400mm or (3000mm) treated pine sleepers.

The pine sleepers are the retaining wall material and are the industry choice for retaining walls. They are treated to protect them from fungal and termite attacks and are non-arsenic, making them a good choice for vegetable gardens or areas adjacent to where children play.

You want enough sleepers to encompass the total final length and height of the wall, plus a few extras for capping and posts. A good rule of thumb is to have each sleeper post to be 600mm long, plus the weight of the wall below the capping.

In terms of supplies, you’ll also need a post-hole digger, circular saw, tape measure, a spirit level, stringline, shovel, set out paint, power drill and a crowbar.

Steps to Building a Retaining Wall

Step 1 – Use your handy post-hold digger to do what it does best – excavate two end post holes 600mm deep each.

Step 2 – Use your circular saw to cut your sleeper posts to the correct length: 600mm plus the height of the wall and 150mm for the final adjustment.

Step 3 – Take your sleeper post and stand it in one of the holes vertically. Use your spirit level to ensure it’s plumb and level.

Step 4 – Fill up the hole halfway with water, then pour in the quick-set concrete you have prepared. As soon as possible, re-plumb the post and check that it is level. Leave the concrete to set, which should take about 20 minutes. Repeat the process for the other end post.

Step 5 – Take your stringline and run it between the two end posts. Use the shovel to excavate a shallow trench on the garden side. You want it deep enough so the bottom sleepers will rest just below the grass.

Step 6 – Now it’s time to mark the desired position for the interval posts with set-out paint. For 2400 mm sleepers, we recommend making the intervals 1200mm apart. For 3000mm sleepers, it’s recommended to mark them 1500mm apart. Then dig a post hole at each interval 600mm deep. Set a post in each post hole 600mm deep.

Step 7 – Pull out your power drill and use it to attach the sleeper posts horizontally to the vertical posts, starting from the bottom part of the trench, with 100mm bugle head screws.

Step 8 – Make sure the posts are level and use the flat side of the crowbar to tap them into place if needed. Stagger the joints between adjacent rows on the next layer of sleepers until all the sleepers reach the top of posts.

Step 9 – Mark the posts that are level with the top layer of the sleepers and use a circular saw to remove excess post length.

Step 10 – Finally, finish the wall with your sleepers laid on top flatly to create a garden ledge that can be sat on or used for gardening purposes.

Need Help Building Your Retaining Wall?

Our experience, professionalism & workmanship is the best in Adelaide when it comes to retaining wall supplies & installation. We pride ourselves on delivering quality products & service, so you won’t be disappointed!

We have a variety of standard or custom retaining walls to choose from. If you’re not sure which one will suit your needs best we are happy to give you some advice & recommendations, making your final decision easier.

Visit our showroom, call, or request a quote today.