How to Build a Retaining Wall
Last Updated Oct 17, 2011 · Written by Rob Schneider
Do you live on a sloping block that is preventing you from having a level patio area in your backyard? Do you want your flower bed to stand out as a feature in your garden? A retaining wall can be a great solution to so many home landscaping problems. If you're willing to get your hands dirty, it is a job you may be able to do yourself. All you need to know are the basics of how to build a retaining wall. After that, it's just a matter of getting started.
Retaining Walls: Legal Restrictions
Because retaining walls have to support a great deal of weight, DIY retaining walls are restricted to one metre or less in height. If you want to build a retaining wall any higher than that, you must engage the services of a structural engineer
. If you are planning on building a large retaining wall or an extensive network of walls, you may also need to get a building permit from your local council, so check with council before you begin
This quick guide to how to build a retaining wall assumes you will be building a wall of less than a metre in height. Is this you? If so, let's get started:
How to Build a Retaining Wall: First Steps
The first step toward building a retaining wall is to prepare the groundwork:
- For a straight wall, set pegs and a string line. For a curved wall, lay out your curve using a string attached to a peg at the centre of the arc you want to create.
- Scrape away dirt to mark the area and remove the string.
- Dig a trench approximately 15cm deep by 60cm wide.
- Add gravel followed by 25mm sharp sand or metal dust. Fill to approximately 10cm from ground level.
- Compact gravel and sand. Use a spirit level at intervals to make sure your gravel bed is level. NOTE: If you are installing on a sloping bed, make your bed stepped. It is very important that your bricks are laid level; otherwise there is a danger of movement over time.
How to Build a Retaining Wall: Your First Course of Blocks
When you are satisfied that your groundwork is ready, lay your first course of blocks. This first course is the most important, so use your spirit level to check that it is level and your string and pegs or peg to check that your retaining wall is straight or follows your desired curve. When you are satisfied, backfill and fill the front of your first course with gravel or dirt. At least 100mm of the first course of blocks should be covered front and back by dirt or gravel. This will help prevent later movement of the wall.
As you lay further course of blocks, backfill and compact as you go. If you do not, the dirt will settle over time and you will find you have to continually add more backfill.
Choosing Your Retaining Wall Materials
A good way to make the job easier is to find a retaining wall system
that features interlocking blocks and blocks specially designed for curves and 90 degree angles. These systems also include capping and other decorative features that standard concrete or stone blocks do not.
Because retaining walls have to support a great deal of weight, taller and wider walls should also be provided with drainage, since the added weight of water could conceivably cause the wall to collapse. If you feel that this may be a danger, consult a retaining wall
expert in your area and get their advice or help. A retaining wall is definitely one job that has to be done once and done right, so don't take any chances.