Rats live under decks because the space gives them overhead cover from predators, close to food and water. The reliable fix is a three-step sequence: confirm and trap the colony, then seal the perimeter with buried hardware cloth so new rats cannot re-dig the same spot.
- Trap before you seal. Sealing a colony in place does not remove it, it just relocates the problem.
- Rats chew through chicken wire. Only 1/4-inch galvanized hardware cloth stops them.
- Avoid poison under a deck. A poisoned rat dies in an inaccessible spot and smells for weeks.
- Remove food and harborage or a new colony moves in behind the old one.
Confirm the Burrows
Norway rats dig burrow entrances two to four inches across with smooth edges and fan-shaped excavated soil. Tunnels run about 18 inches deep with hidden escape holes nearby. Confirm which entrances are active by loosely plugging them with newspaper or grass and rechecking in 24 to 48 hours; displaced plugs mean a live burrow.
Look for rice-shaped droppings, gnaw marks on deck framing and wiring, and a sharp ammonia smell on warm evenings.
Trap the Colony
Rats are neophobic, meaning they avoid new objects, so pre-bait unset snap traps for two to three days before arming them. Place traps along walls, beams, and runways near the burrow entrances, not out in the open. Peanut butter is the most reliable bait.
Skip the poison. A poisoned rat that dies under the deck rots in an inaccessible spot, and the carcass is a secondary-poisoning risk to pets and wildlife. Traps give clean, confirmed removal.
Rats follow edges and familiar routes, so place traps against the deck frame and along runways. Trap first, then seal. If you seal every gap while rats are still inside, they chew a new exit and the problem gets worse.
Seal With a Buried Barrier
Once trapping activity drops, seal the deck perimeter. Dig a trench about 12 inches deep along the deck edge and install 1/4-inch galvanized hardware cloth, bending the buried portion outward into an L-shape so rats cannot dig under it. Secure the top edge tightly to the deck frame.
Chicken wire is not sufficient; rats chew straight through it. Backfilling the trench with loose stone adds another layer of digging discouragement.
Remove the Attractants
Rats stay where food, water, and cover overlap. Move bird feeders away from the deck, bring pet food in at night, secure trash and compost, pick up fallen fruit, and trim the bottom foot of vegetation around the deck. Clear woodpiles and clutter that give rats cover.
Recheck the barrier yearly, especially after freeze-thaw cycles that can shift buried mesh.
When to Call a Professional
Call a professional if the colony is large, if activity persists after two weeks of trapping, or if rats have chewed wiring or structural framing. A pro can identify the species, locate every burrow, and install a proper exclusion barrier. Rat removal with exclusion typically runs $300 to $600. Still deciding whether to handle this yourself? My DIY vs. pro quiz asks five questions and gives you a straight answer.
Frequently Asked Questions
Rats dig under the deck edge or squeeze through gaps at the perimeter. A deck gives them overhead cover from predators, and they stay if food and water are nearby. Any gap the size of a quarter is an entrance.
No. A deck provides shelter, warmth, and cover, so rats have no reason to leave while food is available. You have to trap the colony and then seal the space to prevent re-entry.
No. Poisoned rats often die in inaccessible spots under the deck, creating an odor problem, and the carcass can poison pets and wildlife. Trapping followed by exclusion is the cleaner, more reliable method.
A quarter-inch galvanized hardware cloth, buried 12 inches deep and bent outward in an L-shape. Rats chew through chicken wire and plastic, so the mesh must be galvanized steel.
With pre-baiting and trapping, most of the colony is caught within one to two weeks. Full removal plus sealing the perimeter usually takes a few weeks, depending on the size of the colony.
