A groundhog living under your deck is more than a nuisance. A single groundhog can excavate up to 700 pounds of dirt while building its burrow system, and that displaced soil weakens the footings and foundation your deck relies on. The good news: you can evict the animal humanely and seal the space so it doesn’t come back.
Why Groundhogs Choose Decks
Decks offer exactly what groundhogs look for in a den site: overhead cover from predators, dry soil that’s easy to dig, and proximity to food sources like gardens and lawns. The gap between the ground and the deck’s framing gives them a ready-made entrance, so they can start tunneling immediately rather than digging from scratch in an open field. Once established, a groundhog will treat the space as a permanent home, expanding the burrow over months and returning to it year after year.
How to Confirm It’s a Groundhog
Groundhog entrance holes are 10 to 12 inches in diameter, noticeably larger than what skunks or rabbits leave behind. Look for a mound of loose dirt and small rocks piled near the opening, often fan-shaped. A single burrow system can have up to five holes: one main entrance and as many as four secondary exits, so check the full perimeter of your deck and any nearby structures.
You may also notice wide, flattened trails in the grass leading to and from the holes. Groundhogs are diurnal, meaning they’re active during the day, so you’ll likely spot the animal itself in the morning or late afternoon feeding on clover, dandelions, or garden vegetables.
Structural Damage to Watch For
The primary risk is soil displacement. When a groundhog removes hundreds of pounds of earth from under your deck, it creates voids beneath footings and support posts. Over time, those supports can shift or settle unevenly, leading to a deck that feels spongy, slopes to one side, or pulls away from the house.
The tunnels also redirect water. Rain and snowmelt that would normally drain away from your home can follow the burrow channels instead, pooling under the deck or seeping into a crawl space or basement. This creates long-term moisture problems, including mold and further erosion of the soil supporting your structure. If electrical wires or irrigation lines run through the area, groundhogs can chew through them with their powerful incisors, adding the risk of short circuits or water damage from broken pipes.
Collapsed tunnels are another concern. The loosened dirt above a burrow can cave in under the weight of a person walking across the lawn, creating ankle-twisting sinkholes near the deck.
Timing Matters: When to Evict
Groundhogs breed shortly after emerging from hibernation in March, and females give birth about a month later. The young stay in the burrow for roughly two months before leaving to establish their own territories. That means from April through June, there’s a real chance baby groundhogs are inside the burrow. Evicting or sealing the entrance during this window can trap dependent juveniles underground, where they’ll die.
The safest time to evict is mid-July through September, after the young have dispersed but before the animals enter hibernation. Avoid winter eviction too. Groundhogs hibernate from roughly October through February, and sealing a burrow during this period traps a dormant animal inside.
How to Get Them Out
One-Way Exclusion Doors
A one-way door is a short tunnel or flap mounted over the burrow entrance that lets the groundhog leave but prevents it from re-entering. This is the most reliable DIY method, but it only works if you seal every other opening at the same time. If you install the door on the main entrance but leave a secondary exit open, the groundhog simply walks back in through the other hole.
After installation, the groundhog will try to dig back in once it realizes it’s locked out. Professionals bend their underground barrier material into an L-shape at the base to block this digging. Expect the groundhog to test the barrier for one to three days before giving up and relocating. Once you’re confident the animal is gone (no new digging, no fresh dirt at the entrances), remove the one-way door and permanently seal that last opening.
Live Trapping
In many states, landowners can live-trap and relocate groundhogs with permission from the landowner of the release site. Ohio, for example, allows trapping year-round but requires each trap to be labeled with your name and address and checked every 24 hours. Rules vary significantly by state and municipality. If you’re trapping within city limits, check local ordinances first, as some towns restrict or prohibit trapping entirely.
Place a large cage trap (at least 12 by 12 by 36 inches) near the main burrow entrance, baited with apple slices, cantaloupe, or fresh broccoli. Partially cover the trap with a dark cloth to make it feel more like a tunnel. Once you catch the animal, relocate it promptly to a wooded area with good ground cover, at least five miles away, to reduce the chance it returns.
Sealing the Deck Permanently
Eviction without exclusion is temporary. Another groundhog, skunk, or raccoon will eventually discover the same space. The permanent fix is installing hardware cloth or welded wire mesh around the entire perimeter of your deck, buried underground with an L-shaped footer to prevent digging.
Here’s what works:
- Trench depth: Dig at least 12 inches down along the deck’s edge. In sandy or loose soil, go 18 inches.
- L-footer: Bend the bottom of the mesh outward at a 90-degree angle so it extends 12 to 18 inches horizontally underground, forming an L. This stops animals from digging straight down next to the barrier.
- Wire gauge: Use heavy-duty welded wire, ideally 6-gauge (about 5 mm thick) with galvanized coating. Thinner gauges like 19 or 20 will corrode underground within a few years and won’t resist chewing.
- Mesh opening: No larger than 2 by 2 inches. Groundhogs won’t fit through this, and it also excludes skunks and rabbits.
Attach the above-ground portion of the mesh to the deck frame with screws and washers, then backfill the trench firmly. The L-footer is the critical detail most people skip. Without it, a determined groundhog can dig under a straight vertical barrier in a single night.
Deterrents That Help (and Don’t)
Ammonia-soaked rags, predator urine, and commercial repellent granules are commonly recommended, but their effectiveness is limited and temporary. A groundhog with an established burrow is unlikely to abandon it because of a bad smell. These products work best as a supplementary measure after eviction, discouraging a new animal from investigating while you finish installing permanent barriers.
Vibration stakes (solar-powered devices that pulse into the ground) have some anecdotal support but no strong evidence behind them. If you want to try non-lethal deterrents before committing to exclusion work, combining strong scent deterrents with vibration devices near the entrance gives you the best shot. Just don’t rely on them as a long-term solution.
Repairing the Damage
Once the groundhog is gone, inspect the area under your deck before sealing it up. Fill collapsed tunnels with a mix of gravel and compacted soil to restore support under footings. If any deck posts have visibly shifted or settled, you may need to jack them back to level and pour new concrete footings. Check for chewed wires or damaged irrigation lines, and look for signs of water channeling toward your foundation. Redirecting downspouts and regrading the soil around the deck can prevent the drainage problems that groundhog tunnels often create.