Cockroaches get into apartments through two main routes: they’re carried in on everyday items like grocery bags, cardboard boxes, and secondhand furniture, or they crawl in through gaps in walls, pipes, doors, and shared infrastructure between units. In apartment buildings specifically, the most common path is migration from a neighboring unit through wall voids, plumbing lines, and wiring channels that connect one apartment to the next.
Understanding which route applies to your situation matters because the fix is different for each one. Here’s how each entry method works and what you can do about it.
Hitchhiking on Everyday Items
The German cockroach, the small tan-brown species most common in apartments, rarely comes in from outdoors. It’s almost always introduced through infested items brought inside. Grocery bags, beverage cartons, and cardboard boxes are classic carriers. The corrugated structure of cardboard creates perfect hiding spaces, and boxes picked up from supermarkets or stores may already be infested before you bring them home.
Secondhand furniture is another major source. Used couches, dressers, and especially kitchen appliances can harbor cockroaches and their egg cases in joints, crevices, and motor housings. Small electronics are surprisingly risky too. Cockroaches are attracted to the warmth generated by coffee makers, toasters, alarm clocks, computers, and gaming consoles. They’ll nest inside these devices and travel with them when you move.
Other commonly overlooked carriers include:
- Shoes and luggage picked up after travel or storage
- Potted plants, where cockroaches hide in the soil, under leaves, or on the pot itself
- Laundry and linens that have been stored in infested spaces
- Deliveries in cardboard packaging, especially from warehouses
This is why a perfectly clean apartment can suddenly have cockroaches. Cleanliness helps prevent them from thriving, but it doesn’t stop them from arriving in the first place.
Migration From Neighboring Units
In multi-unit buildings, cockroaches travel between apartments through shared walls, ceilings, pipes, wires, and other openings that connect units. German cockroaches spend most of their time hidden in cracks and crevices, but they’re highly mobile and routinely move between adjoining apartments using these internal pathways.
This is one of the most frustrating entry routes because it’s largely outside your control. If a neighboring unit has an infestation, cockroaches will spread outward looking for new food and water sources. They move through plumbing chases (the vertical shafts where pipes run between floors), electrical conduit openings, gaps around shared ductwork, and any unsealed penetration in a common wall. A building’s infrastructure is essentially a highway system for cockroaches.
This is also why treating a single apartment often fails to solve the problem in a larger building. The roaches retreat into wall voids or adjacent units during treatment and return once conditions are safe again.
Entry From Outdoors
Larger species like American and Oriental cockroaches typically enter from outside. American cockroaches prefer dark, moist areas and congregate in basements, crawl spaces, floor drains, sump pumps, boiler rooms, and sewer systems. During warmer months, they’re also found outdoors in yards and around trash containers, and they often travel long distances from their nesting sites to find food.
Oriental cockroaches follow a similar pattern but tend to stay at ground level. They live outdoors under stones, debris, and leaf litter, entering buildings through door thresholds, vents, and foundation-level openings. Inside, they settle in cool, damp spots like basement floor drains and cellars.
Both species get in through gaps around windows, doors, vents, utility openings, and even in firewood carried inside. Any crack or gap that leads from the exterior, a basement, or a crawl space into your living area is a potential entry point.
What Keeps Them Once They’re In
Getting inside is only half the equation. Cockroaches stay and reproduce when they find the right combination of warmth, moisture, food, and shelter. German cockroaches are drawn specifically to kitchens and bathrooms because these rooms provide all four. They hide in cracks under sinks and toilets, behind refrigerators and dishwashers, near trash containers, and inside cabinets and pantries. As opportunistic feeders, they’re attracted to crumbs, spills, grease residue, and garbage.
Water matters as much as food. A dripping faucet, condensation under a refrigerator, or standing water in a drain can sustain a cockroach population even in an otherwise clean apartment. They also gravitate toward warm appliances: the motor area behind a refrigerator, the underside of a dishwasher, and the interior of toaster ovens and coffee machines all provide the heat and shelter they prefer.
How to Block Entry Points
Physical exclusion, creating barriers that prevent cockroaches from getting in, is one of the most effective prevention strategies. Cockroaches can flatten their bodies to squeeze through remarkably small gaps, so thoroughness matters.
Start with the spots where pipes and wires enter your walls. Use silicone caulk to seal cracks around baseboards, wall vents, electrical outlets, and plumbing penetrations. Install tight-fitting door sweeps on all exterior doors and replace worn weatherstripping around windows. In an apartment, pay special attention to the wall you share with neighboring units and to areas under sinks where plumbing passes through the wall.
Drain covers on floor drains and sink drains can block sewer-dwelling species from climbing up into your space. If your building has gaps around shared ductwork or large openings where pipes enter from a common chase, mention these to your landlord, as sealing them benefits the entire building.
Combine exclusion with eliminating food and water access. Store food in sealed containers, clean up crumbs and spills promptly, take out garbage regularly, and fix any leaks. Without moisture and food, even cockroaches that make it inside are less likely to establish a colony.
Preventing Hitchhikers When You Move
If you’re moving, especially from a building with a known cockroach problem, take precautions to avoid transporting them to your new place. Launder all clothes and linens before packing. Shake out shoes and inspect electronics. Wash and dry all pots, pans, and cooking utensils, then pack them immediately.
If an infestation was severe, consider discarding small appliances like coffee makers and alarm clocks rather than risking transport. Inspect potted plants carefully, checking the soil for movement and examining leaves, stems, and the pot itself. Use new boxes or plastic bins for packing rather than cardboard from unknown sources. These steps take time but can prevent you from importing a problem into a clean apartment.
Who’s Responsible in a Rental
In most jurisdictions, landlords are responsible for preventing and addressing insect infestations in rental properties. Housing codes generally require landlords to maintain pest-free conditions, and when an infestation occurs, the landlord is typically responsible for extermination unless a specific tenant is found to be causing the problem.
If you discover cockroaches, notify your landlord in writing as you would with any repair issue. In some cities, a housing code inspector can require the landlord to follow a structured extermination program for the building. If the inspector determines that one tenant’s behavior (such as accumulated garbage) is the source, that tenant may be cited instead. The key point is that cockroach problems in apartment buildings are usually a building-wide issue, and effective treatment requires a coordinated response across multiple units, not just your own.