Before you start, plan out the length and height of your retaining wall. We are replacing an old retaining wall, but the same principles apply to one that you start from scratch. Our retaining wall will be two sleepers high, but you can make it lower or higher depending on your requirements.
Use a tape measure to work out the length of your wall and how much timber you'll need. Make sure you leave some space at the back for a drainage pipe.
Choose timber with a minimum rating of H4. We've gone for treated pine sleepers, which are designed to go in ground, and will last longer out in the weather and soil.
Depending on the length of your wall, the sleepers are going to need joiner posts to keep them in place. So, measure and mark the points where the posts will go.
Lay out where you are going to build your retaining wall by running a string line between two stakes at either end. Make sure you set your string line to the back of the retaining wall. This will help you keep your posts in line and your retaining wall straight.
Dig holes for the posts the same depth as the height you want the posts to be above ground. We are also digging a bit further out from the string line because our posts will be in front of the wall.
Measure the height of your posts from the bottom of the hole to the top of the string line. We will be cutting enough timber for three posts, but you may need more.
Now it's time to cut your timber to the sizes you need for the wall and posts. Measure and mark your timber using a pencil and square, then use a circular saw or handsaw to cut the timber.
Once you have your timber cut to size, put the posts into position. Make sure they are far enough out to go in front of the wall.
Place a wall sleeper behind the first end post, and attach it using your drill. Then attach the other end to the next post. Repeat this process with each sleeper until the bottom row is completed. Then, work your way down the same way for the top row of sleepers.
Use a pencil and square to mark the height you need for the posts to be flush with the wall. Then, use your saw to cut off the tops of each post.
Now, mix up some concrete according to the directions on the packaging and pour it into the holes around the base of each post. Cover each hole with soil and let the concrete set. It's a good idea to brace your posts first, so that they stay in line when you're pouring the concrete, and while it's setting.
Pour a layer of scoria behind the wall and place your drainage pipe directly on top. Cover the pipe with another layer of scoria and then cover that with soil. Make sure to run the end of the pipe to a spot where it can be accessed. Direct it to a suitable stormwater drain on-site or into a garden area.
You can also attach single sleepers face down on top of your wall. They not only look good but also double as seating when you want to spend some time out in the yard with your family and friends. Then, all you have to do is stain or paint your wall.
Asbestos, lead-based paints and copper chromium arsenic (CCA) treated timber are health hazards you need to look out for when renovating older homes. These substances can easily be disturbed when renovating and exposure to them can cause a range of life-threatening diseases and conditions including cancer. For information on the dangers of asbestos, lead-based paint and CCA treated timber and tips for dealing with these materials contact your local council's Environmental Health Officer or visit our Health & Safety page.
When following our advice in our D.I.Y. videos, make sure you use all equipment, including PPE, safely by following the manufacturer’s instructions. Check that the equipment is suitable for the task and that PPE fits properly. If you are unsure, hire an expert to do the job or talk to a Bunnings Team Member.