Can a Fence Be Used as a Retaining Wall?
It's a question we hear surprisingly often:
"Can I use my fence to hold back soil?"
The simple answer is no.
Although a fence may look strong enough to support soil, it isn't designed to withstand the enormous sideways pressure created by retained earth. Using a fence as a retaining wall can lead to bowed panels, leaning posts, structural failure and expensive repairs.
In this guide, we'll explain why fences and retaining walls are designed for completely different jobs, what happens when soil is piled against a fence, how you can safely deal with changes in ground levels, and what you can do if a neighbour has built up their garden against your boundary.
Why a Fence Isn't Designed to Retain Soil
A fence is designed to resist forces such as:
- Wind loading
- The weight of the fence itself
- Occasional impact
A retaining wall, however, has to withstand constant lateral pressure from tonnes of soil. That pressure increases even further after heavy rainfall, when the ground becomes saturated.
Even a relatively small difference in ground level can place significant force on fence posts and panels over time.
This is why fence manufacturers generally advise that fencing should never be used as a retaining structure.
What Happens If Soil Is Piled Against a Fence?
Increased Pressure
The weight of the soil pushes continuously against the fence. Over time this can cause:
- Fence posts to lean
- Panels to bow
- Fixings to loosen
- Complete structural failure
Moisture Damage
Timber performs best when it is allowed to dry naturally between periods of wet weather. Soil held against a fence keeps the timber damp for long periods, increasing the risk of decay and shortening its lifespan.
Fence panels should never be in direct contact with soil. Keeping the panels clear of retained earth helps maximise their lifespan.
Reduced Airflow
Air circulation helps timber dry out. Soil packed tightly against a fence restricts airflow, trapping moisture and creating ideal conditions for fungal decay.
Choose a Fence Built to Last
If your fence is being installed near raised ground levels or in areas that are regularly exposed to damp conditions, choosing a high-quality fence becomes even more important.
Look for fencing that comes with a long guarantee, such as 25 years, as this is often an indication that the timber has been properly treated and manufactured for long-term performance.
However, even the best fence will have a reduced lifespan if it is incorrectly installed or used as a retaining wall.
Can Concrete Fence Posts Hold Back Soil?
Concrete fence posts are stronger than timber posts, but they are still not designed to function as retaining walls.
Although the posts themselves are robust, the overall fence system has not been engineered to resist the continuous sideways forces created by retained ground.
Can You Turn a Fence Into a Retaining Wall?
Sometimes, but not by asking the fence itself to do the retaining.
Instead, the retaining element should be installed first, allowing the fence to continue performing its intended role of providing privacy and security.
Timber Sleepers
Timber sleepers are one of the most popular solutions for retaining soil beneath a fence.
The sleepers retain the soil while the fence sits above them, safely clear of the retained earth. Depending on the height difference, sleepers can be stacked to form a retaining wall before the fence is installed.
Concrete Gravel Boards
For smaller changes in ground level, stacked reinforced concrete gravel boards fitted between concrete fence posts can retain modest amounts of soil while keeping the fence panels above ground level.
This solution is suitable for relatively small differences in level but should always follow the manufacturer's recommendations.
Timber Gravel Boards
Timber gravel boards can also help protect the bottom of a fence from soil and moisture.
Although they often look similar to the fence panels above them, timber gravel boards are frequently manufactured using more durable timber and undergo a more intensive treatment process. This makes them stronger and more resistant to decay than standard fence panels.
They are designed to take the moisture and wear that would otherwise affect the fence itself, helping extend the life of the installation.
Purpose-Built Retaining Walls
Where there is a significant change in ground level, the safest solution is a dedicated retaining wall constructed from reinforced concrete, concrete blocks or another engineered retaining system.
The fence can then be installed independently behind or above the retaining wall.
How Much Soil Can Be Retained?
There is no single answer, as it depends on:
- The type of fence posts.
- The retaining system being used.
- The type of soil.
- Drainage behind the retaining structure.
- The height of the retained ground.
As a general rule, the greater the difference in ground level, the less suitable it becomes to rely on any fence system to retain soil.
What Can I Do If a Neighbour Piles Soil Against My Fence?
If your neighbour raises the level of their garden and piles soil directly against your fence, the additional pressure can cause damage that the fence was never designed to withstand.
Before the situation escalates, it's worth having a friendly conversation. Many people simply don't realise that a boundary fence is not intended to retain soil.
You could politely explain that:
- The fence wasn't designed to hold back earth.
- The pressure from the soil may cause it to lean or fail.
- Soil traps moisture and can significantly reduce the fence's lifespan.
- A separate retaining structure is the correct engineering solution.
If damage has already occurred, take photographs and keep records of any conversations.
Frequently Asked Questions
Can a closeboard fence retain soil?
No. Closeboard fencing is designed as a boundary fence, not as a retaining wall.
Can concrete gravel boards retain soil?
Yes, for relatively small changes in ground level they can, particularly when multiple reinforced gravel boards are stacked between suitable concrete fence posts.
Will gravel against a fence cause problems?
Gravel drains much better than soil and exerts far less pressure. However, it should still not remain in direct contact with timber fence panels.
Can sleeper fencing retain soil?
Timber sleepers can form part of a retaining structure if specifically designed and installed for that purpose.
Does a fence guarantee cover damage caused by retained soil?
Usually not. Damage caused by using a fence as a retaining wall is unlikely to be covered under the manufacturer's guarantee.
Conclusion
A fence and a retaining wall may sit alongside one another, but they perform completely different roles.
If you need to hold back soil, install a suitable retaining structure first. Whether that's timber sleepers, stacked concrete gravel boards or a purpose-built retaining wall, the aim is always the same: keep the soil away from the fence panels and allow the fence to do the job it was designed for.
Combined with a quality fence backed by a long guarantee, proper installation and good drainage, this approach will maximise the lifespan of your fencing and help prevent costly failures in the future.
