Dirt Leaking from Your Retaining Wall? Here’s What You Need to Do
“We noticed a small pile of dirt that appears to be coming out of what looks like a drain at the base of our retaining wall. We haven’t had any rain lately, so we’re unsure if it’s a drainage issue or something digging behind it. Any idea what’s happening or who we should call to look at it?”
— Reddit user, r/homeowners
A pile of dirt near your retaining wall might not look like a big deal at first, but it’s often a clue that something’s gone wrong behind the structure. Whether it’s a drainage issue, poor backfill, or even animal activity, the wall may be under pressure, and if left unchecked, the damage can worsen over time.
We’ll break down what’s likely happening, how to tell if your retaining wall needs attention, and what can be done to fix it properly. If you’ve spotted something similar in your garden or yard, here’s what you need to know before it turns into a bigger problem.
What's Causing Soil to Spill from the Wall?
When soil starts spilling out from your retaining wall, especially through a drainage hole or small gap, it’s a clear sign that something’s happening behind the structure. Let’s go through the most common causes.
1. Animal Activity
One possible reason is that an animal is digging behind the wall. Rodents, such as rats, mice, or even gophers, can burrow into loose soil, creating tunnels that lead to open weep holes or pipe outlets.
If the dirt coming out is dry, loose, and crumbly, and there’s been no rain, this is often a clue that a critter has made its way in. You might also spot small tunnels or disturbed soil on top of the wall or nearby.
2. Poor Backfill Material
If your wall were filled with regular soil instead of crushed rock or drainage aggregate, it could slowly wash out over time. Even small amounts of water can carry fine soil particles through the wall’s drainage system if there’s no proper separation layer (like geofabric).
This is one of the most common causes of soil loss behind retaining walls. If not fixed, it creates hollow spaces that weaken the wall’s support.
3. Missing or Clogged Drainage
Most retaining walls require proper drainage, typically a slotted pipe (also known as an agi pipe) installed behind the wall to direct water away. If this is missing, blocked, or not installed correctly, water pressure builds up behind the wall.
When that pressure finds a way out,ike through weep holes or cracks, it often brings soil with it. Over time, this can lead to bulging, leaning, or even collapse.
4. Heavy Rains Without Protection
Even if it hasn’t rained recently, previous weather events can still have a significant impact. If a wall was exposed to heavy rain in the past without proper drainage, the effects might only start to show now, especially if the soil has shifted or settled.
Each of these problems can be fixed, but the key is understanding what’s actually going on behind the wall. A proper inspection is the best way to determine that.
Why This Is a Problem
When you see dirt coming out of a retaining wall, it may seem harmless. However, this small sign can point to a much bigger problem lurking beneath the surface. Here’s why it matters.
Soil Loss Creates Empty Spaces Behind the Wall
When dirt escapes from behind the wall, it leaves gaps where solid support used to be. These hollow areas reduce the wall’s strength. Over time, the pressure from the ground above can exert itself against these weak spots, rendering the wall unstable.
Water Pressure Builds Up
If the wall’s drainage system is blocked or poorly designed, water has nowhere to go. As water builds up behind the wall, it increases the pressure on the structure. This is called hydrostatic pressure. Too much of it can cause the wall to bulge, lean or even collapse.
The Wall May Start to Move
When soil shifts or water pressure becomes too strong, the wall can begin to lean forward or crack. These early movements are warnings that the structure is no longer holding as it should.
Repair Costs Rise Over Time
Fixing a small drainage issue now is much easier and cheaper than rebuilding a failed wall later. Ignoring the early signs can lead to more severe structural problems and costly repairs.
Safety Risks
A collapsing retaining wall can damage nearby structures, fences, or garden beds, and even pose a danger to people walking in the area. It is not just a matter of looks; it can be a real safety concern.
If you notice soil spillage, cracks, movement, or drainage issues, it is best to address them early.
There's Also a Safety Side to This
If the wall is holding back soil near a house, a shed or a garden area where kids play, failure is more than just cosmetic. We’ve seen walls collapse after heavy rain or erosion, and the damage can be dangerous and expensive.
If soil is spilling out or your wall appears to be starting to lean, it’s time to have it checked properly.
What Not to Do
When something looks off with a retaining wall, it’s tempting to try a quick fix or hope it sorts itself out. I’ve seen many homeowners take these steps with good intentions, but they often end up making things worse. Here’s what I always advise against.
Don’t Block the Drainage Hole
If you see dirt coming out of a pipe or weep hole, your first instinct might be to cover it up or seal it off. Please don’t. Those outlets are designed to allow water to escape. Blocking them traps water behind the wall, which builds up pressure and causes bigger problems. The soil is a concern, yes, but stopping the water flow will only speed up the damage.
Please don’t Fill the Gap Without Checking What’s Behind It
Sometimes people pack the hole with gravel or try to patch it with concrete. But without knowing where the soil is going or how much has been lost, you could be hiding a bigger issue. You need to know what’s happening behind the wall before you try to seal anything up.
Don’t Ignore It
Even if the wall still looks solid, the damage behind it can grow quickly. Once the soil starts to move or water becomes trapped, the structure becomes weaker over time. What starts as a small pile of dirt can turn into a major lean or collapse. It’s always better to act early.
Don’t Assume It’s Just Animals
Critters do dig behind walls, and yes, sometimes that’s all it is. However, upon closer inspection, we often find poor drainage, inadequate backfill, or missing pipes. If you write it off as just a burrow, you might miss a serious underlying problem.
How Our Team Fixes a Failing Retaining Wall
Every wall is a bit different, but when someone calls us about soil spilling out or drainage concerns, we follow a clear process. It’s not just about fixing what you can see — we look deeper to make sure the whole structure is stable and draining properly.
Step 1: We Inspect the Site
First, we take a proper look at the wall. We check for signs of movement, cracks, leaning or bulging. We’ll also have a look at how the wall was built, what kind of material is behind it and how water is supposed to drain away.
If you’ve found a pile of dirt near a drainage outlet, we’ll determine whether it’s just an animal burrow or something more serious, such as soil being washed out by trapped water.
Step 2: We Check the Drainage and Backfill
Next, we expose a small section behind the wall to see what’s going on inside. A strong retaining wall should have clean crushed rock or drainage aggregate behind it, with a slotted ag pipe to carry water away.
If we find loose soil instead of rock, no geofabric or a missing pipe, that tells us straight away that the wall wasn’t built to last. Sometimes we also find a drainage pipe that’s blocked or sitting too high, which means water has been building up instead of draining away.
Proper drainage is essential for long-term stability, which is why it’s part of Australian industry standards like AS 4678 – Earth Retaining Structures. These guidelines help make sure retaining walls are built to handle pressure, movement and weather conditions safely.
Step 3: We Repair or Rebuild as Needed
If the issue is minor and the rest of the wall is intact, we can often repair the problem area by addressing the drainage and replacing the backfill. However, if the wall is leaning or has lost significant soil support, we may need to rebuild that section from the ground up.
That means creating a proper, compacted base, installing the right drainage, using quality backfill, and rebuilding the wall with the correct materials and techniques. We build every wall as if it’s meant to last for decades.
Step 4: We Make Sure It Won’t Happen Again
Once the wall is back in shape, we take steps to prevent future problems. That might include laying geofabric to stop soil mixing with gravel, adjusting surface water flow above the wall or adding a rodent-proof grate to any exposed pipe.
The goal is to leave you with a wall that not only looks strong but also holds up through all kinds of weather and ground movement.
When to Call a Professional
Not every wall problem necessitates a full rebuild, but certain signs are clear warnings that it’s time to bring in a professional. These are the things we look for—and the reasons why early action makes a significant difference.
Soil Keeps Spilling Out
If you’ve cleared away the dirt and more keeps appearing, there’s likely an ongoing issue behind the wall. Whether it’s animals digging, water movement or both, this is something we need to investigate before it causes structural damage.
The Wall Is Leaning or Bulging
Even a slight lean is a sign that pressure is building behind the wall or that the footing is starting to give way. A wall should stay upright and stable over time. If it’s shifting, there’s a deeper problem that needs to be fixed.
Cracks Are Starting to Form
Hairline cracks may not appear serious, but they’re often the first indication of movement or water pressure behind the wall. If cracks are growing or spreading, it’s best to have our team assess them before they get worse.
Drainage Outlets Are Blocked or Missing
Weep holes or slotted pipes help water escape safely. If you can’t find any, or if they’re covered up, that could mean water is building up behind the wall. This adds extra pressure and increases the chance of failure, especially after rain.
There’s a Sudden Dip or Gap Behind the Wall
If the ground behind your wall appears to be sinking or separating from the top of the wall, that’s a sign that the backfill has washed away. This leaves the wall unsupported and more likely to move.
We’re always happy to come out and take a look. Even if the problem turns out to be small, it’s better to know for sure. And if repairs are needed, we’ll guide you through the best way to address the issue properly and ensure it lasts.
Frequently Asked Questions
It might seem like an easy fix, but sealing the hole could trap water behind the wall, making the problem worse. That hole is likely part of the wall’s drainage system. It’s more important to find out why soil is escaping in the first place.
A properly built retaining wall with correct drainage and backfill can last 20 to 50 years, sometimes longer. The key is using the right materials and building it to suit the site conditions. Most walls that fail early weren’t built to spec from the start.
It depends on the site, but we often recommend concrete sleepers or reinforced block walls for strength and durability. Timber can be effective in some cases, but it has a shorter lifespan and is more susceptible to rot and termite damage if not properly treated.
In many areas, yes — especially if the wall is over a certain height (usually 1 metre) or if it’s supporting a structure or boundary. We can help guide you through the necessary permits and assist with drawings or engineering if required.
The cost depends on the size of the wall, the extent of the damage, and the materials used. Small repairs start from a few hundred dollars, while full rebuilds can range into the thousands. We offer on-site assessments so you get a clear quote before any work begins.
We Can Help Fix It Safely and Permanently
If your retaining wall is leaking soil, showing signs of movement, or doesn’t seem right, it’s worth getting it checked before the situation worsens. These issues rarely resolve themselves, but with the right solution, they can be addressed quickly and effectively.
Our team specialises in building and repairing retaining walls that last. We know what to look for, how to fix it, and how to prevent it from happening again. Whether it’s a small section or a full rebuild, we’ll give you a clear plan and honest advice.
Contact us today for a complimentary site inspection and quote.
We’ll come out, take a look and let you know exactly what’s going on — no pressure, no fuss.
