How To Build a Fence on Top of Retaining Walls

First Published: 7 June 2016 | Updated: 8 November 2021

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Building a fence on top or behind a retaining wall is rather easy despite how intimidating it may sound.

Fences and railings are a common sight around retaining walls. At Australian Paving Center, we frequently get asked if homeowners can install this themselves. What we usually say to them is: it varies. What could work for one may not work for the other as there are many factors that need to be considered.

We’ve compiled everything you would need to know from starting your project to building your fence.

What’s Considered A Retaining Wall?

A retaining wall is a structure built from different types of materials whose main purpose is to retain soil behind it.

Despite the wide variety of materials you can use to build retaining walls, it is advisable to choose a material that will be persistent despite the weather. You wouldn’t want to rebuild your wall every now and then, would you?

Before You Start With Your Project

As we’ve mentioned earlier, building a fence on top of a retaining wall involves the consideration of many factors. Like with any home project, planning for your project is as vital as the construction itself.

Is Council Approval Required?

Before starting any wall projects on your yard, it is imperative that you be compliant with your building approval. Most council approvals are needed for any type of excavation of land. This applies to any excavation that is related to construction or building of any project. If you have an already built a retaining wall before, then you are aware of how it works.

If this is your first time, you would need to check with your local council if approval is actually needed. Remember that the general difference in ground level is what’s measured. If you’re planning to have a retaining wall in a tiered fashion, then the overall difference from the ground level must be less than one metre. Otherwise, you will need approval for your wall.

Should You Give Notice To The Neighbouring Land Owners?

You should give notice to your neighbour. You wouldn’t want your neighbour to start construction that will affect your side of the lawn without telling you, right? This should be done even if you don’t need council approval.

What Kind Of Work Affects Your Neighbouring Land?

Any filling within 600mm of the boundary will affect your neighbour’s land. This includes any excavation extending downwards at a slope from a point of 600 millimetres below natural ground level.

Type Of Notice

You should give a notice of intention to perform the work as well as the nature of the work that needs to be done. This notice should be given at least 28 days prior to starting your project.

Failing to Give Notice

If you failed to notify your neighbour and started with your fence anyway, your neighbour has the right to file a complaint against you. A fine of up to $10,000 will be charged.

Building Your Own

All fences have the ability to resist some type of load. One advice we always give to people is to remember that a fence will add additional overturning force to their wall. This means that there’s an additional weight to your retaining wall since fences can be overturned by strong winds.

A properly designed and a well built retaining wall can prevent any future mishap such as having the top of your wall collapse.

The key here is to consider the material you will use for your wall and the material you need for your fence. Ensure that the wall has an adequate amount of resistance. Pick a material sturdy enough to retain soil and still keep with the additional force of having a fence installed. Ensure that your PVC pipes are properly installed within your wall blocks since they will act as a support for your fence post.

Installing Fences in Different Ways

Installing fences can be done in three different ways. This will be a good reference as you plan the structure of your wall and fence on top.

3 Feet Behind The Block

The most ideal distance to place your fence is at a minimum of 3 feet behind your wall. This type of design helps keep the pressure off your wall and makes for a sturdy build.

Behind the Block

It is common to install a fence behind the retaining wall block. If you want your fence placed closer to the wall at more than 3 feet you will need the help of a professional to do the design to ensure that the top of your wall can resist the forces from the fence.

Top Of The Wall Block

Installing your fence post on top of the wall block is the most challenging of the three. You’ll need an engineer to analyze your wall before any installation can be done. If your wall has a height of 200-400mm then the fence can be built directly on top of the wall. Have your fence post pass through your wall blocks and secure them with concrete.

When You Already Have A Wall

If you’re planning to install a fence when you’ve already had a retaining wall built, it will be more challenging. The best way to dig the soil is by hand. This will keep any damage minimal on your geogrid. A geogrid is a material used to reinforce the soil.

The best way to install a fence in this kind of situation is to have it installed 3 feet behind the wall block. Even fence installers will have a challenging time installing the fence directly unto the block.

DIY Or Hiring A Professional

Hiring a professional or installing the fence yourself depends on your plan and on how you want to design your yard. The decision will depend on the height of your retaining wall. Remember that there are factors you need to consider and careful planning will produce better results.

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