How to Get Rid of Groundhogs Under Shed: Trenching and Exclusion

Groundhogs (Marmota monax) are prolific excavators capable of moving up to 35 cubic feet of soil to construct a single burrow system. When they tunnel beneath a shed, they compromise the structural integrity of the foundation, create severe tripping hazards, and provide a conduit for secondary pests like skunks and snakes. Eradicating a groundhog presence requires a two-phase approach: humane eviction followed by permanent physical exclusion. Relying solely on repellents or trapping without addressing the subterranean void will result in immediate reinfestation by transient wildlife.

Confirming the Culprit: Groundhog vs. Other Burrowers

Before initiating eviction, verify that a groundhog is the active tenant. Sheds often attract multiple species, and misidentification leads to failed exclusion efforts. According to University of Maryland Extension, groundhog burrows have distinct architectural signatures:

• Entrance Dimensions: Main entrances are 10 to 12 inches in diameter. Smaller 4-inch holes indicate skunks or opossums.
• Soil Displacement: Groundhogs push excavated dirt out in a plow-shaped mound, typically 1 to 3 feet wide, right at the lip of the entrance.
• Secondary Holes: A single groundhog family will maintain 2 to 4 secondary escape holes (plunge holes) located 10 to 30 feet from the main entrance, often hidden under dense brush or directly under the shed's opposite corner.
• Chew Marks: Look for distinct, parallel incisor gouges on the shed's wooden siding or nearby garden hoses, typically 1/8-inch wide.

Phase 1: The One-Way Door Eviction Protocol

You cannot install permanent exclusion fencing while the animal is still inside, or you will trap it beneath your shed, leading to desperate digging, structural damage, and a rotting carcass. Use a one-way exclusion door to allow the groundhog to leave but prevent re-entry.

Step 1: The Newspaper Activity Test

Locate all suspected burrow entrances around the shed perimeter. Loosely plug every hole except the primary entrance with wadded newspaper or dry leaves. Wait 48 hours. If the newspaper at the primary entrance is pushed out, the burrow is active. If the newspaper remains undisturbed but a secondary hole is cleared, the animal is using the secondary hole as its primary exit.

Step 2: Mounting the Exclusion Door

Purchase a 12x12-inch galvanized steel one-way wildlife door (approx. $35-$45). Clear all vegetation and loose soil from a 14-inch radius around the active entrance. Anchor the door frame securely into the soil using 8-inch landscape spikes, ensuring the swinging flap opens outward. Seal the perimeter of the door frame with hardware cloth and dirt so the groundhog cannot squeeze past the edges.

Step 3: Monitoring and Removal

Leave the door in place for 3 to 5 days. Check the flap daily. Once the flap remains closed for three consecutive nights, and the newspaper inside the burrow (placed gently through the door gap with a stick) remains undisturbed, the burrow is empty.

Phase 2: Permanent Exclusion via L-Footer Trenching

Once the shed is confirmed empty, you must seal the perimeter. Groundhogs are powerful diggers but poor climbers. The industry standard for preventing subterranean intrusion is the L-Footer trench, which exploits their instinct to dig straight down when encountering an obstacle.

1. Dig the Trench: Dig a trench 12 inches deep and 6 inches wide around the entire perimeter of the shed. If the shed sits on a concrete slab, dig the trench flush against the concrete edge.
2. Cut the Hardware Cloth: Use 14-gauge, 1-inch hexagonal galvanized hardware cloth. Cut strips that are 36 inches wide.
3. Form the 'L' Shape: Bend the bottom 12 inches of the hardware cloth at a 90-degree angle to create an 'L' profile. The 24-inch vertical section will go into the trench; the 12-inch horizontal section will point outward, away from the shed, resting on the trench floor.
4. Secure and Bury: Attach the top of the vertical wire to the shed's wooden skids or siding using heavy-duty fencing staples or galvanized screws with washers. Backfill the trench, ensuring the outward-facing horizontal wire is buried 12 inches below the soil surface.

When a new groundhog attempts to dig under the shed, it will hit the vertical wire, dig straight down, hit the horizontal outward-facing wire, and eventually abandon the effort rather than backing up and digging further out.

Material Cost Breakdown (10x12 Foot Shed Perimeter)

Deterrent Efficacy Matrix: What Actually Works?

Homeowners frequently attempt chemical or sonic deterrents before resorting to physical exclusion. The Humane Society of the United States notes that habitat modification and physical barriers are the only long-term solutions. Below is an efficacy matrix of common deterrents when applied to shed perimeters.

When to Call a Professional Wildlife Operator

While DIY exclusion is highly effective for standard sheds, certain scenarios require a licensed nuisance wildlife control operator (NWCO). You should hire a professional if:

• Structural Compromise: The shed is sinking or tilting, indicating the burrow system has hollowed out a massive void directly beneath the load-bearing skids. A pro will use hydraulic jacks and specialized trenchless filling compounds.
• Concrete Slab Foundations: If your shed sits on a poured concrete pad, groundhogs will tunnel under the slab, causing it to crack. Pros use ground-penetrating radar to map the void and inject polyurethane foam to stabilize the slab without breaking the concrete.
• Multiple Families: If you count more than 4 active plunge holes around a large shed, you are likely dealing with overlapping territorial claims of multiple families.

Cost Expectations: As of 2026, professional groundhog eviction and basic perimeter trenching for a standard 10x12 shed ranges from $350 to $600. If concrete slab stabilization or structural jacking is required, costs can escalate to $1,200 or more. Always verify that the operator holds a current state wildlife damage permit and carries liability insurance, as improper trapping can result in steep municipal fines for illegal relocation of rabies-vector species.