How to Avoid Retaining Wall Disasters

How to Avoid Retaining Wall Disasters

If you have a section that lacks character, or is sloping and difficult to maintain, putting in retaining wall blocks or a retaining wall can create something attractive or even spectacular while making your section far more manageable.

Sometimes this can be a simple DIY project using some reclaimed railroad tiles or logs for small walls up to one-foot high. But if you require something higher with an aesthetically pleasing view, it is best to call in the professionals.

When building a retaining wall, being aware of these five retaining wall problems will ensure you never face a disaster.

1. Supply Proper Drainage

Poor drainage is usually the biggest problem with retaining walls. When it rains, the soil gets wet, and this puts further strain on the wall. If this moisture freezes, then thaws, extra pressure builds up, and poorly designed walls are at risk of failure.

Adequate drainage allows water to leave the structure. The choice of materials used for the wall becomes a key factor when it comes to drainage. Weep holes drilled into the wall at regular intervals can drain water through the wall.

Behind the wall, a drainage pipe can be installed, running the full length of the wall and sloped to carry water to an outlet location.

2. Build on a Sturdy location

Just like any building project, having a suitably sold base to build on is crucial.

The foundation needs to be sturdy enough to resist any heavyweight. Ideally, the foundation should be twice the width of the wall, with the wall located in the centre.

If building a concrete wall, to prevent cracking, footings should be placed underneath the wall using crushed rock or a thick layer of compacted gravel. This works well in conditions where the soil is particularly dry.

3. Choosing Appropriate Plants

With the wall built and looking great, you might think you can choose any of your favourite plants. But that could be a big mistake.

Because drainage is so important to keeping the structural integrity of any retaining wall, you need to choose plants that will survive and thrive in dry conditions. This is because the design of your wall is constantly removing water from the soil.

You also need to be aware of how fast the roots grow. Larger shrubs and trees with fast-growing and wide-spreading roots can gradually destroy the structure of your retaining wall.

Finally, you need to understand how each plant will react to the soil if your wall is built from concrete or limestone gravel. Those materials make the soil more alkaline. This means acid-loving plants like azaleas, rhododendrons, and hydrangeas will struggle to grow unless you can keep the pH level low enough for them to survive.

4. The Higher the Wall, the More Support Needed

Retaining walls above four feet in height become far trickier to build. Instability will occur if the wall is not adequately supported. The higher the wall, the greater the amount of pressure it has to withhold.

High timber walls will need Deadman timbers and anchors to stop the wall from starting to lean outwards due to underground pressure. Extending the footing may also be necessary.

With higher walls, you should also check to see if you require building consent. There’s nothing worse than spending lots of money building a beautiful retaining wall and garden, then having to spend even more pulling it all apart, redesigning and building it all again.

5. Pick your Contractor Carefully

Like many trades’ occupations, not all contractors deliver quality results. Not all of them have qualifications, and some lack a history of successful builds.

Consider your budget, and don’t be enticed by the lowest cost. Compare quotes from at least three companies, and most importantly, look at their earlier work. Photos are good, but even better would be to visit the homes where they have done work and physically view the finished work and how well it looks several months after completion.

Make sure that what you are wanting is exactly what the contractor is going to provide.

You will want to be sure that the materials chosen will be sturdy and complement your surroundings. At the same time, the design has to be both an architectural and functional feature in your garden.


You need to regularly check for each of the following:

  • Pooling water in the soil and dry weep holes after rain – both are signs that your drainage system isn’t working.
  • Leaning, cracking, and bulging –are signs that there is too much pressure building up behind the wall.
  • Weeds – pull them out because over time they can compromise the walls’ structure.
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