Snakes get into houses through surprisingly small openings, most of which homeowners never notice. A snake can squeeze through any gap as small as half an inch, and baby rattlesnakes can fit through spaces as narrow as a third of an inch. If you can see daylight around a pipe, door frame, or foundation crack, a snake can likely use it as an entrance.
The Most Common Entry Points
The typical house has dozens of potential snake entry points. The most frequent ones are gaps under doors, cracks in the foundation, and spaces around garage doors that don’t seal flush with the ground. Broken window screens, pet doors, and dryer vents mounted on exterior walls are also common culprits. Even the gaps where utility pipes and wires pass through the foundation often leave enough room for a snake to slip inside.
Brick homes have a specific vulnerability: weep holes. These are the evenly spaced, unmortared gaps in the lower rows of brick that allow moisture to drain from behind the wall. They’re intentional and serve an important purpose, but they’re also open invitations for snakes, rodents, and lizards. Homeowners frequently discover snakes entering and exiting through these holes. Specialty vent covers designed for weep holes can block wildlife while still allowing airflow and drainage.
Rooflines and attics are less obvious but well-documented routes. Snakes are capable climbers and can follow tree branches to a rooftop, then enter through gaps in soffit vents or where the roof meets the wall. Rat snakes, which can grow to over four feet long, are especially adept at climbing vertical surfaces and frequently end up in attics while following rodent trails.
Yes, They Can Come Through Plumbing
It sounds like an urban legend, but snakes do occasionally enter homes through the plumbing system. Every toilet, shower, and sink connects to a network of drain pipes that eventually leads to the sewer line or septic tank. If there’s a crack in a sewer line, a loose septic tank cover, or a gap where the toilet meets the floor, a snake can enter the drainage system and work its way indoors.
There’s also the vent stack, a vertical pipe that extends from your plumbing system through the roof to release sewer gases. A snake on the roof can drop into this open pipe and travel downward through the system, eventually emerging in a toilet bowl. The S-trap or P-trap (the curved section of pipe that holds standing water under every drain) usually acts as a barrier, but a determined snake can push through it. These incidents are uncommon, but they happen often enough that plumbers and wildlife removal services consider it a known entry route.
What Draws Snakes Inside
Snakes don’t enter homes randomly. They’re following food, seeking shelter from temperature extremes, or both. Because snakes can’t regulate their own body temperature internally, they constantly move between warmer and cooler spots in their environment. In early spring, they gravitate toward warm surfaces like sun-heated foundations, stone patios, and metal structures. In summer, they seek cool, damp, sheltered spaces, which describes most basements and crawl spaces perfectly.
The single biggest attractant is a rodent population. Snakes are predators, and if mice or rats are living in or around your home, the snakes that feed on them will follow. Bird feeders that scatter seed on the ground, pet food left outdoors, and unsealed garbage all attract rodents, which in turn attract snakes. Stacks of firewood, brush piles, and dense ground cover near the house create the kind of sheltered habitat where both rodents and snakes thrive. Clearing these away from your foundation removes the food chain that brings snakes to your doorstep in the first place.
Which Snakes Show Up Indoors
The species you’re most likely to find inside your house are the ones that already live comfortably around humans. Rat snakes (often called “black snakes”) are the most common home invaders in much of the eastern United States. They’re excellent climbers, strong constrictors, and they follow rodents into attics, walls, and basements. Adults can reach three to over eight feet long, which makes for a startling discovery, but they’re harmless to people.
Milksnakes are another frequent indoor visitor, and they’re regularly mistaken for copperheads because of their similar brownish coloring and banded pattern. In Pennsylvania alone, the milksnake is killed more often than any other species due to this misidentification, despite being one of the state’s most beneficial snakes. Black racers, garter snakes, and ring-necked snakes also turn up indoors regularly.
Venomous species can enter homes too, though it’s less common. In the eastern U.S., copperheads are the venomous snake most likely to be found near houses. You can distinguish venomous pit vipers from harmless species by their eye shape: venomous species in North America have vertical, cat-like pupils, while non-venomous species have round pupils. Venomous pit vipers also have a visible heat-sensing pit between the eye and nostril. That said, trying to get close enough to check a snake’s pupils isn’t a great safety strategy. If you can’t identify it from a distance, treat it as potentially dangerous.
How to Seal Your Home Against Snakes
Effective snake exclusion comes down to eliminating every gap larger than a quarter inch around your home’s exterior. That’s a more demanding standard than most people expect, but baby snakes are remarkably thin. Metal hardware cloth or galvanized steel mesh with gaps no larger than a quarter inch is the recommended material for covering vents, weep holes, and other openings that need to remain functional. Chicken wire and plastic mesh break down quickly and aren’t available in a small enough mesh size to stop snakes.
Start with a methodical walk around your home’s exterior, checking these areas:
- Foundation and slab edges: Look for cracks, gaps where a patio or stoop meets the house, and any spots where pipes or wires penetrate the wall.
- Garage doors: The rubber seal along the bottom degrades over time and often leaves gaps at the corners.
- Door sweeps: Any door with visible light underneath has enough clearance for a snake.
- Dryer vents and exhaust fans: Cover with fine metal mesh if the existing flap doesn’t close tightly.
- Weep holes: Install purpose-built weep hole covers that allow drainage while blocking wildlife.
- Roof vents and soffit gaps: Screen with quarter-inch hardware cloth.
Use concrete patch, expanding foam, or mortar for permanent foundation cracks. For gaps around pipes and wires, steel wool packed into the opening and sealed with caulk works well, since snakes (and rodents) won’t push through steel wool easily.
What to Do If a Snake Is Already Inside
If you find a snake in your house, back away slowly. Sudden movements are more likely to make it flee into a wall void or under furniture, which makes removal much harder. If the snake is in a room with a door, close the door and stuff a towel along the gap underneath to contain it. This keeps the snake in one place and buys you time.
Call a local wildlife removal service or animal control. Professional snake handlers have the tools and experience to capture and relocate the animal safely. Attempting to catch or kill a snake yourself increases the risk of a bite, and in many areas killing certain species is illegal. If you can safely photograph the snake from a distance, that photo will help the removal service identify the species before they arrive.
Once the snake is out, inspect your home for the entry point it used. A snake inside the house almost always means there’s an unsealed gap somewhere. Finding and closing that gap is the only reliable way to prevent it from happening again.