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Retaining Walls, Do’s and Don’t’s.

Susanna Newhart


Retaining Walls have been used since the beginning of time. Ancient cultures used them for agricultural purposes, and a way to re-claim slopes and to level the land. Not much has changed and today you will see them used in landscapes for the same reasons. One big thing that has changed is the products used. In todays blog, I will answer some common questions, and introduce you to Retaining Walls.

Before I begin, I would like to remind you, the best landscaping design starts with a plan. When it comes to Retaining Walls, you do need to be aware of restrictions, and building codes. You may need to reach out and so some research locally, before you even start to dig. After all that, it is important to also address all potential drainage and grading changes after your wall is built.

Can you build a Retaining Wall on a slope?

Absolutely. One of the main functions of a retaining wall is to hold back the soil and to create a more gentle slope. A great way to re-claim a small backyard is to use a retaining wall flatten your space. This is the most common use for walls today. An important factor for this wall to be successful is to ensure there is a drain installed behind the wall. You want to make sure the water does not get trapped. In Edmonton, AB we have some extreme weather changes, and it’s usually very cold for a couple weeks each winter. If you do not have a proper drain, the water stuck behind the wall will expand and contract, and within a very short time push the wall forward and collapse.

Does a Retaining Wall need to be level?

When we build retaining walls, we need to make sure it is level. If you try to build the wall on the same slope as the hill, the weight of the blocks will slowly slide down the hill. If you are trying to build a wall that is not only leveling your yard, but also following a hill you need to step the wall down. To maintain a safe load on the retaining wall, the wall should lean into the hill a minimum of 1 inch for every 12 inches of height. Its a bit difficult to explain fully in a short blog. Essentially you will build long steps that follow the contour of the hill. If you want more information, you can arrange an on site visit, Newhart Landscaping and Construction Ltd.

What can I plant behind a Retaining Wall?

Low retaining wall make wonderful garden beds, these give height and help bring the eye up to the house. In beds like this you can plants some larger shrubs. I do not recommend you planting them too close to the wall itself. Remember that drain we talked about earlier? It sits behind the wall, and you don’t want roots to get into that. Keep all shrubs back a bit to avoid that issue. For tiered beds, that are taller and are holding back more of the soil, I suggest no trees or larger shrubs. Its best to have either just sod, or very small plants with shallow roots.

How do you retain soil on a slope?

Build a Retaining Wall! If the retaining wall is build properly they can hold a great deal of weight. They should not be installed over 3′ without consulting an engineer.  There are different products for each application. Some products can not hold back as much, will others hold an immense amount of weight. Making the right choice for the application is the job of your designer or contractor.

How deep should the footing be for a Retaining Wall?

This is very dependant on the height of the wall and what the function of the wall will be. There are four basic types of walls. They are gravity walls, piling walls, cantilever walls and anchored walls. Gravity are for shorter heights. Piling walls use piles to stabilize the wall and are used in more commercial settings. Cantilever walls have a ‘leg’ that run perpendicular to the wall. And Anchored walls which are similar to cantilevers, but use geo-textiles to anchor them into the slope. Each type of wall has its own applications, and again your designer or contractor will be the best person to tell you which one you need.

What products are available for Retaining Walls?

There are so many colours, textures and styles! Wood beams are the least expensive, you can stain it to match your deck or fence. It does break down a bit faster, and I do not suggest you use it to hold back a large amount of soil. Wood is great for the lower beds in your yard where you would like to create a bit of heights. Natural Rock is amazing, and has a number of different colours. Some are more round, while others you can have them to be quite square. They can hold back more soil than wood, but you will need about 30% more product due to waste. Natural stone tends to be a bit more bulky, I use it when a client has a bit bigger yard with more space. Wall blocks are the most versatile of the three. You can build them higher, they can hold the most weight, and they have the most different colours and styles. There is even a product that we use quite a bit that look like natural wood, called Borealis from Techo-Bloc , just to mention one!

The basics of Retaining Walls haven’t changed in thousands of years. We pretty much build it the way the Romans build theirs over 2000 years ago. They are becoming more popular, as more people become educated in the proper applications. Have a plan, ask your designer and you will be able to enjoy your backyard space to the fullest!