Groundhogs (Marmota monax) are common in many suburban and rural environments across North America. Their natural instinct to burrow creates a major problem when they choose the area beneath a house or foundation for their home. These robust rodents are powerful excavators, capable of digging extensive tunnel systems up to 50 feet long and six feet deep. When these burrows are constructed beneath structural supports, porches, or foundations, the resulting soil displacement can compromise the structure’s integrity, leading to costly damage. Addressing an infestation requires accurate identification, safe eviction, and the installation of permanent physical barriers.
Confirming the Target and Entry Points
Effective groundhog management begins with correctly identifying the animal responsible for the damage. A groundhog hole is typically large, measuring eight to 12 inches in diameter, and is marked by a visible, fan-shaped mound of excavated dirt at the primary entrance. This differs from the smaller holes created by skunks or the volcano-shaped mounds left by moles.
Groundhog burrows usually feature one obvious main entrance and several secondary, less visible escape holes. Before attempting exclusion, locate all active openings to ensure the animal does not become trapped inside. To confirm if a hole is active, loosely pack the entrance with crumpled newspaper or light soil and check it the following day. If the blockage has been pushed out, the burrow is currently in use. This confirmation is necessary before installing any exclusion device, such as a temporary one-way exit door, to ensure the animal can be forced to leave before permanent sealing.
Physical Exclusion: Installing Structural Barriers
The only reliable, long-term solution to prevent groundhogs from digging under a house is the installation of a specialized structural barrier known as an “L-foot” or “L-apron.” This method physically blocks the animal’s ability to tunnel beneath the foundation or slab by creating a perimeter defense that extends both vertically into the ground and horizontally away from the structure.
A trench must be dug around the entire perimeter of the protected area, such as a deck or foundation, aiming for a depth of at least 12 inches. The barrier material must be heavy-gauge, galvanized wire mesh, often 1/4-inch or 1/2-inch hardware cloth, as chicken wire is too weak and should be avoided.
The wire mesh is secured directly to the side of the structure. The bottom section is bent outward at a 90-degree angle, creating the “L” shape that extends horizontally for 6 to 12 inches away from the foundation. This horizontal apron acts as a subterranean false floor, deterring the groundhog when it attempts to dig down and encounter the mesh.
Once the L-apron is positioned, the excavated soil is backfilled and compacted over the horizontal wire section. This process ensures the groundhog cannot dig straight down or push the barrier away. The focus remains on the buried apron to block entry beneath the structure.
Safe and Legal Eviction Methods
If a groundhog is confirmed to be living under a structure, it must be safely evicted before structural barriers are installed. One common method uses live cage traps, typically placed five to ten feet from the active burrow entrance. Because groundhogs are wary, wearing gloves when handling the trap helps avoid transferring human scent, significantly increasing the likelihood of a catch.
Effective bait includes fresh garden produce like cantaloupe, sweet corn, or peas. Once an animal is trapped, the immediate concern is the legal requirement for its disposition, as regulations vary significantly by state and municipality. Relocating a trapped groundhog is often illegal or strictly regulated, requiring the animal to be released on site or humanely euthanized.
An alternative is installing a one-way exclusion door directly over the main burrow entrance. This simple metal flap allows the groundhog to push its way out but prevents re-entry. After confirming the animal has exited, the door is removed, and the permanent structural barrier is installed. Remember that cornered wildlife can be defensive, so use appropriate safety precautions.
Discouraging Future Digging
Once the structural barrier is in place and existing groundhogs have been evicted, long-term prevention focuses on making the area less attractive to new animals. Groundhogs are drawn to locations that offer easy access to food and adequate cover.
Habitat modification involves eliminating dense vegetation, overgrown bushes, or wood and rock piles near the foundation to remove potential hiding spots. Food sources must also be managed by promptly removing fallen fruit and protecting garden vegetables with separate fencing.
Sensory deterrents, such as cayenne pepper, garlic, or commercial granular repellents, can be applied near the perimeter to create an unpleasant environment, as groundhogs are sensitive to strong odors. Motion-activated sprinklers can also startle them.
However, these deterrents are temporary and not a substitute for physical exclusion, as their effectiveness diminishes quickly due to rain or evaporation. The most effective long-term deterrent remains the combination of habitat modification and a robust, permanent L-foot barrier around all vulnerable structures.