A groundhog is a large rodent that creates extensive burrow systems, which can pose a significant problem when excavated beneath human structures. They are drawn to the space under a deck because it offers sheltered protection from predators and weather, combined with soil that is often easier to dig than compacted open ground. A single groundhog can displace hundreds of pounds of soil, compromising the stability of deck footings and potentially creating trip hazards. Addressing this issue requires a phased approach: first encouraging the animal to leave, then safely excluding it, and finally implementing structural modifications to prevent future occupation.
Immediate Non-Invasive Deterrents
The initial approach involves making the area beneath the deck uncomfortable for the groundhog, encouraging it to relocate without physical intervention. Groundhogs rely heavily on their sense of smell to feel secure, so introducing strong, unpleasant odors can disrupt their sense of safety. Placing cotton rags soaked in ammonia, or commercial predator urine granules, near the burrow entrance can signal danger, suggesting the presence of a threat like a fox or coyote.
Another method involves using intense spices, as groundhogs dislike the irritating nature of capsaicin. Spreading a mixture of cayenne pepper or garlic powder around the burrow entrance and surrounding deck perimeter may deter the animal. These sensory deterrents should be reapplied frequently, especially after rain, to maintain a consistent level of discomfort.
Visual and auditory disturbances can also prompt a groundhog to seek a quieter location. Motion-activated lights or sprinklers near the den entrance can startle the animal. A battery-powered radio placed beneath the deck and tuned to a talk station creates a constant, unpredictable noise. The goal is to make the environment unpredictable and unwelcoming, leading the diurnal groundhog to abandon the site during its active hours.
Safe Removal and Burrow Exclusion
Once non-invasive methods have been attempted, the next step is to ensure the groundhog has permanently vacated the burrow before any sealing occurs. A simple method to confirm the animal’s absence is the “flour test,” which involves dusting a layer of flour or placing loosely wadded paper in the burrow entrance. If the flour or paper remains undisturbed for 24 to 48 hours during the groundhog’s active daytime period, the animal is likely gone.
If the animal is still present, a one-way exclusion door can be installed over the main entrance. This device, typically constructed from sturdy wire mesh like galvanized hardware cloth, acts as a temporary funnel. It allows the groundhog to push its way out but prevents re-entry. It is important to cover all other known secondary entrances before installing the exclusion device, forcing the animal to use the one-way exit.
The use of one-way funnels requires caution, particularly during late spring and early summer, which is the groundhog’s birthing season. Sealing a nursing female out of the burrow will result in the starvation of her kits, so it is necessary to confirm the young are independent before exclusion. Following a confirmed absence, the entrance should be permanently sealed using a durable material like concrete or heavy-gauge hardware cloth that extends several feet into the soil.
Long-Term Structural Prevention
The most effective strategy for preventing future groundhog infestations involves installing a robust, permanent barrier around the entire perimeter of the deck. This is accomplished using a technique known as an “L-footer” exclusion barrier. This method requires digging a trench at least 12 inches deep and extending outward from the deck’s edge by 12 inches. Heavy-duty galvanized wire mesh, often referred to as hardware cloth, is secured to the underside of the deck framing and lowered into this trench. The bottom portion of the mesh is then bent outward at a 90-degree angle, creating the ‘L’ shape. When the trench is backfilled, any groundhog attempting to dig beneath the deck will encounter the outward-facing wire apron, which physically prevents them from tunneling deeper toward the structure.
In addition to the physical barrier, modifying the surrounding environment makes the area less appealing to burrowing animals. Groundhogs are herbivores, so removing potential food sources like fallen fruit or low-hanging garden vegetables near the deck can reduce the attraction. Clearing dense, low-lying vegetation or piles of debris eliminates the natural cover groundhogs prefer for shelter and concealment. Regular inspection of the wire barrier is recommended to ensure that rust, shifting soil, or animal gnawing has not created a new vulnerability in the perimeter defense.