Build Your Own Retaining Wall

Do you have a problem area on the border of your garden and you’re just note quite sure what to do with it? Chances are the border of your garden would look great with a raised garden bed full of colour and foliage. This easy to follow guide to install a HARDAZ retaining wall system can solve all your problems from leveling a lawn, giving structure to your garden border or even an easy way to build a raised vegetable garden.

What you’ll Need

  • Tools
  • Shovel or post-hole digger
  • Tape measure
  • String line
  • Level
  • Drainage aggregate such as blue metal or scoria
  • Materials
  • Sleepers (either 50mm or 75mm)
  • HardAz posts
  • Rapid Set Concrete
  • Agricultural drainage pipe
  • Drainage aggregate such as blue metal or scoria


The first step in your project is to check your local council requirements to see if you need to comply with any regulations. If you’re planning on working with a large amount of earth it is also recommended that you consult an engineer.

Next is to draw up on paper your desired retaining wall. If possible plan using readily available sleeper lengths to avoid having to cut the sleepers. Check with your local Mitre 10 which lengths they have in stock.

Make a list of the number and size of sleepers that you’ll require. Allow for the first sleeper to be embedded around 100mm into the ground.

Make a list of the number and type of HardAz posts that you’ll require. The space between posts is suggested to be around 1200mm. Around half the length of the posts will be below ground level. For example, a 900mm high retaining wall will require 1800mm posts.

Step 1- Dig Post Holes

Mark and dig the post holes at the planned spacing. Remember to dig the holes the same depth as the wall will be high.

Step 2- Insert and Level Posts

Using a string line to ensure the retaining wall is straight and level, concrete the posts into the ground ensuring the required height is achieved (taking into account the first rail being imbedded 100mm into the ground) and that the posts line up and are vertical. If the retaining wall steps down at any point ensure it steps down at the same height as your rails.

As you proceed from post to post, place into position the intervening bottom sleeper. That will allow the next post to be better positioned. Using the string line and level ensure the post is horizontally and vertically level, then concrete into position. Repeat the procedure for remaining posts.

Step 3- Drop in Sleepers

Slot in the timber sleeps, ensuring the first sleeper is embedded 100mm into the ground. Prior to back filling, suitable drainage is recommended such as slotted agricultural drainage pipe laid in a trench of drainage metal.

TIP: Seal sleeper cut ends with suitable timber preservative to resist rotting.

Step 4-Add Capping

An optional finish to your retaining wall is to cap the retaining wall with a row of sleepers laid horizontal.

The final step is to back-fill your retaining wall and you’re ready to add your plants or lay your turf!

Beams for your Wall

Simply decide whether you need 50 or 75mm thick sleepers and the height of your wall. Then choose which posts you require to finish the job.

H Beam Posts


For use in straight line retaining walls.

C Beam Posts


For finishing the end of a retaining wall

Joiner Posts

For use in straight line retaining walls.

End Posts

For finishing the end of a retaining wall.

Corner Posts

For creating the perfect 90º corner.