Best Practices For Retaining Walls

Offering reliable landscaping services to homeowners in British Columbia since 2013

Picture of Natasha Maerz

Natasha Maerz

Owner/Office Manager

When thinking about adding a retaining wall to your outdoor space, it can get overwhelming trying to figure out if you are going to DIY or hire a company, what material you should use (there are a variety of materials for  wood retaining walls or concrete retaining wall), and how much to budget for. While you are in charge of your project, and have the last say, there are a number of things that MUST be done, so that your retaining wall not only looks great, but lasts.

At Back 40 Landscaping our expertise is in building Allan Block retaining walls. We are trained and Certified in building Allan Block retaining walls to best practices, and have a passion for building retaining walls that actually last. 

So, what are the best practices for retaining walls?

Best material to build a retaining wall

If you are looking for a wall that is the focal point of your outdoor space, will last a lifetime, and is backed by professional engineers, then an Allan Block concrete wall in our opinion is a great option for your landscape wall.  While some homeowners like the look of a wood retaining wall, a wall that is built with pressure treated lumber will not last. A wood retaining wall has a life expectancy of 10 years, while a  concrete retaining wall is a lifetime product. 

This is because pressure treated lumber is not rated for ground contact, meaning it is meant to stay off of the ground, never touching soil. This is obviously impossible to do when building a retaining wall out of wood, making Allan Block the best material to use for a retaining wall.

Hardscape projects located in British Columbia, Canada with products manufactured by Expocrete an OldCastle Company.

Building a retaining wall

When it comes to building a retaining wall, the structure and the look of the wall should be homeowner’s main concern. It might be tempting to want your wall built quick, and as cheap as possible, but cutting corners and not using the proper amount of material will only cause headaches for homeowners in the long run.

When excavating the soil where the retaining wall is going to go, it can be hard not to cheat how much retained soil is getting excavated. The more retained soil that is excavated, the more gravel that is going to have to be put in its place, and the higher the cost of disposing the soil. The problem with this is that if you cheat the excavation, and do not add enough gravel, your retaining wall will fail. Gravel is essential to the base of the wall to provide a solid level of foundation to build the wall on, and will allow water to drain through the gravel, providing proper drainage. When there is no standing water, there will be no pressure put against the wall, and no frost heave in the winter time.

Other things that aid to the strength of a retaining wall is burying the first row of the retaining wall blocks  so that the wall doesn’t slip out, and core filling the back, front, and middle of the wall with gravel.  Typically, contractors do not put enough gravel behind the wall because more gravel is used, and the cost of labor and material goes up.

To get a retaining wall to look straight, and not have any waves in it, is actually a lot harder to do than it appears to be. If you look at retaining walls in your neighbourhood, you will probably see walls that are not completely straight. To get a wall that is straight takes quite a bit of time and skill. This is done by string lining the brick, laying each retaining wall block brick one at a time, and making sure that the brick is level from side to side, and front to back. This process ensures that your wall will be in a straight line.


Designing a retaining wall

You might think that designing your wall is as easy as figuring out where the wall is going to go, and what it is going to look like, but there are many things that need to be taken into consideration before your wall is built. Building permits are required for retaining walls that are above 4’, and you may need a professional engineer to do the retaining wall design in order to get a building permit. When determining the height of the wall, a detailed understanding of site elevations and grade changes are needed to determine what the height of the wall should be. Remember, a basic retaining wall that is four feet tall and fifteen feet long has to support up to 20 tons of retained soil pressure. With every additional foot of height, the pressure of the retained soil increases substantially. This is why it is important to know what you are in for ahead of the build, so you can make sure that your wall is structurally sound, and will last.

Hiring an expert to build your retaining wall

When it comes to DIY projects, there are a lot of things that homeowners can do to enhance their outdoor space and property without hiring it out. A retaining wall should not be one of them. Retaining walls are built to retain the soil behind them. Building a structurally sound wall requires heavy equipment, a trailer to get materials in and out of the build site, proper planning, and knowledge on how to build the wall. If a wall fails, the retained soil that was being retained by the wall  will collapse, and could cause catastrophic failure. On top of this, the  landscape wall will need to be replaced, causing even more of a headache. These are all things that are better left to a professional who can get the job done right, and allow the homeowner peace of mind.

At the end of your project, you want to be able to trust that your wall is built properly, and looks great.  Avoiding doing any of these best practices for retaining walls may be cheaper upfront, but will cost more in the long run when the wall has to get redone.

Learn about “The ten problems with retaining walls you can’t afford not to know.