Building A Fence On a Wall (Retaining Wall)

Recently on DreamyHome, we talked about the benefits of building a gravel board retaining wall. So first things first, if you’re just getting started out, give that a read. It’ll give you a good foundation for where you’re going to be starting. This should be a nice, quick article, so let’s get right into the nitty-gritty.

To build a fence on a wall, you’ll need to do a few things: get the okay from your local government, notify your neighbours, and get the proper materials.

Now, there’s a bit of nuance to some of these rules, so we should really break them down before we wrap for the day.

Fence on Wall – The Basics

So you’ve decided to build a fence atop your retaining wall. Good choice! Retaining walls offer a good amount of utility, but they’ll also take some extra care and work.

I’m going to assume you’ve read the above article, but just in case you haven’t, we’ll do a very quick recap on what you should know about retaining walls.

Retainer Wall Materials

This is the most subjective part of the whole process. What you use to make your retainer wall is entirely up to you, but each material has its own benefits and trade-offs. We previously covered gravel board retaining walls, but there’s a bit more freedom if you’re just going for any retaining wall.

There are four primary materials that are used for retaining walls, each with its own pros and cons. Keep in mind that a gravel board retaining wall uses the same materials as the first three on the list, so it’s a good stand-in:

Concrete

This is (right next to masonry) by far the sturdiest material to build a retaining wall out of. It’s impervious to water, extremely durable, and heavy as all getout. That means that it’ll be a bit harder to install and remove, and it can also get a bit more expensive than some of the other options here, especially if you’e not laying it yourself.

Wood

The most obvious material with which to build retaining walls is wood. If you’re building a retaining wall as a base for a fence, there are other, better options out there. But on the plus side, it’s cheap, easy to install, and easy to remove when needed. Its major downside is that wood can rot and warp, meaning you’ll likely need to replace it at some point down the line.

Composite (Like PVC)

This is a good middle ground between concrete or masonry and wood. It’s lightweight, impervious to rot, and easy to work with. Unfortunately, it’s also the most expensive (for just raw material). It can also warp with extreme temperature changes, so that’s good to keep in mind.

Masonry

Perhaps the most traditional of all options, masonry is a really great look with longstanding strength and adaptability. It can be easily painted or rendered and holds up well to heavier fences. Its major downside (especially when compared to concrete) is that masonry can soak up moisture and crack if not treated properly. Luckily, a good coat (or three) of masonry paint will seal it right up.

Local Government & Neighbours

The amount that this affects you will vary greatly on where you live. Some jurisdictions will require a process of approval before you can begin projects on your property like this. That goes doubly for retaining walls that are holding fences on property lines. And if you’re in a neighbourhood run by an HOA, good luck – you’ll need it.

In short, the most useful thing you can do in this case, regardless of where you live, is to check in with your local council. They’ll be able to provide guidance on any inspections, fees, and other things to keep in mind. Be sure to notify your neighbours ahead of the project too – if only out of common courtesy.

Of course, depending on where you live, it could be the law that you notify your neighbours at least 28 days ahead of starting any major projects. In these particular instances, failure to do so can rack up some hefty fines, which nobody wants. So do your wallet and neighbours a solid and just give them a written notification before you start the project.

Council approval will also vary depending on how big and high your fence will be, so keep that in mind as well. But don’t worry – we’re getting to that.

Building the Thing

Now we get to the fun bit – actually building the retaining wall and fence. Whether you’re paying someone to do it, or building it yourself, there’s a couple of things to keep in mind:

  1. Weight – This is particularly important with the less-sturdy materials. A properly anchored fence and retaining wall won’t fall over, but if done poorly, it can. It’s good to prepare by assuming your fence will be heavier than it actually will be when finished. This allows you to build for long-term stability, rather than speed of finish. If your fence is made of something heavier than a standard fence, you’ll also need to take that into account.
  2. Wind – Because your fence will be atop a retaining wall, it’s good to plan for wind hitting it a bit more than a standard fence. Especially because a poorly anchored fence can buckle, bend, or snap under the force of high wind. In short, prepare – and think smarter, not harder when building your fence.

There are three ways of thinking when it comes to building your fence – building it atop the retaining wall, building it behind the wall, and building it spaced apart from the wall. Each has its own tradeoffs depending on where you’re building and how high.

Spaced

The ideal spacing for a fence near a retaining wall is roughly 90 cm from the retaining wall. This keeps pressure off of your retaining wall and allows some room to work. With the right amount of space, you can properly anchor your fence and prevent it from tipping in the future.

Behind the Retainer

This is equally possible but will require the help of a professional. This is especially important when building right on property lines. You need to ensure that the fence and retainer remain within your property while still being properly supported. You don’t want to install the fence and proper support, only to have to move it somewhere less ideal because it crosses the property line.

Atop the Retaining Wall

While the most difficult of all methods, it is entirely possible to build a fence atop your retaining wall. You’ll need to bring in an engineer, however, to ensure it can be done properly. Depending on where you live, there could also be regulations in place that affect how high you’re allowed to build. To properly anchor this, you’ll need to account for it while building your retainer wall.

Provide adequate space for your fenceposts to pass through the retaining wall and be anchored in concrete. If you skip this step, you will end up with a toppled fence. And depending on what you used to build the retaining wall, you could have a busted wall, as well.

Final Thoughts

While it’s entirely within the realm of possibility, it’s important that you do your homework before building a fence atop your retaining wall. Depending on where you live, you may need to deal with specific regulations, fees, and inspections, as well as notification of neighbours. While this doesn’t apply to every location, it’s important to know ahead of time. Failure to complete your dues can result in hefty fines and having to rip up or redo your fence.

When you’re finally able to build the fence, it’s important that you plan for how you’re going to do it. Using masonry or concrete will provide the most secure and sturdy retaining wall, while wood and composite can be more easily moved, but suffer in terms of strength and longevity. And if you’re going to be building atop the retaining wall, it’s important to allow for room to drive and properly anchor the fenceposts. If you skip this step, you will end up with a toppled, buckled, or snapped fence and a new (unwanted) project. Now go get building!

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About the Author Harry Thompson

Involved in home renovations throughout his life, Harry is an expert in everything to do with home and garden DIY. In his spare time, he enjoys cooking and tending to his garden.