Something Keeps Tunneling Under My Garden Shed: What Could It Be and What Should You Do?
Discovering mysterious holes or tunnels under a structure on your property can be both confusing and frustrating. Many homeowners eventually face a situation where they notice fresh dirt piles, small holes, or loose soil appearing around buildings like garden sheds, garages, decks, or patios. When the digging seems to happen overnight and the holes keep reappearing no matter how many times you fill them, it raises an important question: what animal is causing it—and could it damage the structure?
This situation is more common than many people realize. Small animals are constantly searching for food, shelter, or nesting locations, and the space beneath a concrete slab or shed can be a very attractive place for them to dig. The problem is that repeated tunneling may eventually affect the stability of the ground beneath the structure.
If you’ve noticed something digging under your shed every night, understanding the possible causes and the safest ways to deal with it can help you protect your property without harming local wildlife unnecessarily.
Why Animals Dig Under Sheds and Concrete Slabs
Before identifying the culprit, it helps to understand why animals are drawn to these areas in the first place.
The ground beneath sheds, porches, and concrete slabs offers several advantages for small wildlife:
Shelter from weather: The structure above provides protection from rain, wind, and extreme temperatures.
Safety from predators: Animals feel safer when they have a roof or barrier overhead.
Soft soil: The edges of slabs or foundations often have loose soil that is easy to dig through.
Hidden nesting areas: Underground tunnels make excellent places to raise young.
For animals that naturally burrow, a shed foundation can look like the perfect ready-made shelter.
Common Animals That Dig Under Structures
Several types of animals are known for tunneling under buildings and concrete slabs. Identifying which one is responsible can help determine the best solution.
Groundhogs (Woodchucks)
Groundhogs are one of the most common animals responsible for large tunnels near structures.
They dig extensive burrow systems with multiple entrances and chambers. A groundhog tunnel can extend several feet underground and up to 20–30 feet long.
Signs of a groundhog burrow include:
-
a hole about 10–12 inches wide
-
a mound of soil outside the entrance
-
tunnels located near fences, sheds, or decks
Groundhogs prefer areas with nearby vegetation, which they use as food.
Rats
Rats are highly adaptable and may dig burrows near buildings, especially if food sources are nearby.
Rat burrows are typically smaller than groundhog tunnels but still large enough to cause concern.
Common signs include:
-
holes around 2–4 inches wide
-
smooth, packed soil near entrances
-
droppings nearby
Rats are especially attracted to areas where garbage, pet food, or compost is available.
Skunks
Skunks sometimes dig under sheds or decks to create a den. These spaces provide quiet protection while they raise their young.
Skunk holes are often about 4–6 inches in diameter.
You may also notice shallow holes in your lawn because skunks dig for insects and grubs.
Moles
Moles are smaller animals that tunnel underground while searching for insects and worms.
Instead of large holes, they usually leave raised ridges of soil or small mounds in the yard.
While moles are less likely to burrow directly under a slab, their tunnels can sometimes extend toward structures.
Chipmunks
Chipmunks create small burrows with several entrances, often near patios, steps, or foundations.
Their holes are usually about 2 inches wide and may not have a noticeable mound of dirt because chipmunks carry soil away.
While their tunnels are smaller, multiple chipmunk burrows can still undermine soil stability over time.
Why the Hole Keeps Reappearing
If you fill a hole and it comes back the next morning, it usually means the animal still lives inside the burrow.
Animals that build underground homes maintain their tunnels carefully. When the entrance is blocked, they often reopen it quickly.
In some cases, the burrow system may have multiple entrances, meaning the animal simply digs another way out.
This is why filling the hole alone rarely solves the problem permanently.
Could It Damage the Shed Foundation?
In most cases, a single small tunnel won’t immediately cause structural damage. However, long-term burrowing can weaken the soil beneath the slab or foundation.
Over time, repeated digging may cause:
-
soil erosion under the slab
-
shifting or settling of the structure
-
cracks in concrete or supports
Large animals like groundhogs pose the greatest risk because their tunnels can extend far beneath the structure.
Addressing the issue early helps prevent more serious problems later.
How to Identify the Animal Responsible
To determine what’s digging under your shed, observe a few details.
Check the Size of the Hole
The width of the entrance often gives the first clue.
Small holes (1–2 inches) usually indicate chipmunks or small rodents.
Medium holes (3–5 inches) may suggest rats or skunks.
Large holes (8–12 inches) often belong to groundhogs.
Look for Tracks or Droppings
Animal tracks in soft soil or droppings near the entrance can help confirm the species.
Early morning observations are especially useful because many animals are active at night.
Use a Camera
A simple motion-activated wildlife camera can quickly reveal which animal is visiting the burrow at night.
This method avoids guesswork and helps choose the right solution.
Humane Ways to Address the Problem
Once the animal is identified, there are several humane approaches to discourage tunneling.
Eliminate Food Sources
Wild animals often stay near places where food is available.
Remove or secure:
-
pet food left outdoors
-
garbage bins
-
compost piles
-
fallen fruit from trees
Reducing food availability encourages animals to move elsewhere.
Use Natural Deterrents
Certain smells and substances may discourage animals from digging.
Common deterrents include:
-
vinegar
-
castor oil-based repellents
-
commercial animal repellents
These products should be reapplied regularly for effectiveness.
Install Underground Barriers
One of the most effective long-term solutions is installing hardware cloth or wire mesh around the base of the shed.
The mesh should extend at least 12 inches underground and outward to prevent animals from digging underneath.
This barrier blocks future tunneling attempts.
Live Trapping
In some cases, humane live traps can capture animals so they can be relocated safely.
However, local wildlife regulations may apply, so it’s important to check local laws or contact wildlife professionals before relocating animals.
Professional Wildlife Removal
If the problem continues or involves larger animals like groundhogs, contacting a wildlife control expert may be the safest option.
Professionals can:
-
identify the species
-
safely remove the animal
-
secure the structure against future burrowing
Preventing Future Tunneling
Once the animal has moved on, preventing future visitors is essential.
Reinforce the Shed Base
Adding gravel, concrete edging, or buried mesh around the foundation discourages digging.
Maintain the Yard
Keep grass trimmed and remove dense vegetation near structures. Animals prefer hidden locations.
Seal Openings
Close any gaps or spaces around the shed where animals might enter.
The Importance of Acting Early
Burrowing animals often begin with a single small hole. Over time, that tunnel can expand into a complex underground network.
Addressing the issue early prevents the burrow from becoming large enough to cause structural concerns.
Even simple steps like installing barriers or removing food sources can stop the problem before it grows.
When to Seek Professional Help
If you notice any of the following signs, it may be time to call a professional:
-
multiple large tunnels
-
visible sinking or cracking near the foundation
-
strong animal odors near the structure
-
aggressive wildlife activity
Wildlife experts have the tools and experience to solve these situations safely and effectively.
Final Thoughts
Finding mysterious tunnels under your garden shed can feel frustrating, especially when the holes keep reappearing after you fill them in. However, this situation is usually the result of common wildlife behavior rather than a serious structural problem.
Animals such as groundhogs, skunks, chipmunks, rats, and moles often dig near buildings because the area provides shelter and protection.
By identifying the animal responsible and using humane deterrents, barriers, or professional help if necessary, you can protect your shed and encourage wildlife to move somewhere more appropriate.
With a little patience and the right approach, it’s possible to solve the problem while keeping both your property and the local wildlife safe.
