Updated
Living in attached housing changes how a cockroach problem behaves. In an apartment building or a row of houses, the roaches in your kitchen may not have started there, and the ones you treat may not be the end of it.
That is why a unit can be spotless and still have roaches, and why treatment in one home sometimes works for a few weeks and then seems to stop. Here is how roaches move through shared walls, what tenants, landlords and rowhouse owners can each do, and how professional roach control fits into a building rather than a single unit.
How roaches move between attached homes
Much of Pittsburgh’s older housing is attached. Rows of brick houses on the South Side, in Lawrenceville, Bloomfield and Polish Hill share a party wall with the house on either side, and many older buildings have been divided into apartments stacked above and below each other.
To a German cockroach, those walls are not barriers. They are highways. Roaches travel through:
- Gaps around pipes where plumbing passes through walls and floors
- Electrical runs, including the space around outlets, switch boxes and wiring holes
- The void inside a shared wall, especially in older plaster and lath construction that has settled and cracked
- Gaps along baseboards and ceilings where a party wall meets the floor or ceiling framing
- Shared basements and utility areas in buildings where these are common
Attached brick rowhouses on the South Side share walls on both sides, so what happens in one home can reach the next.
Plumbing chases are the main route
The most heavily used path in most buildings is the plumbing. Kitchens and bathrooms in stacked apartments are usually lined up vertically so they can share drain and supply lines, and the chase those pipes run through connects every kitchen or bathroom in the stack.
That chase gives roaches everything they want: warmth, moisture from pipes and condensation, darkness, and direct access to the rooms where food and water are easiest to find. Older buildings with steam or hot water heat add radiator pipes that pass through floors and walls as well.
So the places to watch most closely are:
- The cabinet under the kitchen sink, especially around the pipe openings in the back wall
- The space behind and under the refrigerator and stove
- The bathroom vanity and the area behind the toilet
- Where radiator or heating pipes come up through the floor
- Any opening around a dishwasher or washing machine line
Why treating one unit often fails
When one apartment or one rowhouse is treated on its own, three things tend to happen.
The source keeps feeding it
If the unit next door, above or below has an established population, roaches keep arriving through the same routes. Your treatment kills them, but the supply does not stop, so the problem looks like it never goes away.
Roaches get pushed next door and come back
Repellent sprays, especially retail aerosols, drive roaches away from treated areas and into wall voids and neighboring units. When the product wears off, they return.
The population survives in the walls
Treatment placed inside one unit may never reach roaches living in the shared void or in the chase between floors. Those survivors repopulate both sides.
None of that means the treatment in your unit was done wrong. It means the problem belongs to more than one home.
In attached housing, a cockroach problem usually belongs to the building, not just the unit where it was noticed. Treatment works best when the units on every side of the problem, including above and below, are inspected and treated around the same time.
Rowhouses work the same way, without a landlord
Owner occupied rowhouses have the same shared walls as an apartment building, but there is no landlord to coordinate anything. Each owner deals with pests separately unless the neighbors talk to each other.
A middle house in a row shares walls on both sides, while an end house shares only one. Both can receive roaches from next door, and both can pass them along.
If you own a rowhouse and roaches keep returning after treatment, a friendly conversation with the neighbors is worth having. They may already know they have a problem, or they may not have noticed yet. Treating both houses around the same time gives each one a much better chance of staying clear. Roaches do not know where the property line is.
Rowhouses along 22nd Street on the South Side sit wall to wall, which is why a roach problem in one can show up in its neighbors.
How to tell if roaches are coming from next door
It is not always possible to be certain, but certain patterns point to a neighboring source rather than one that started in your home.
- Activity is concentrated along the shared wall or under the sink that backs onto the neighbor’s kitchen
- Roaches appear near pipe openings, outlets or radiator pipes rather than near food
- They come back soon after treatment even though the kitchen is clean, food is sealed and leaks are fixed
- You see them in rooms with little food, such as a bathroom, in numbers that do not match the conditions
- A neighbor mentions roaches, or the building has had problems before
- Small nymphs keep appearing long after the first treatment should have stopped breeding in your unit
For more on reading the evidence, signs of a hidden cockroach problem covers droppings, odor and egg cases in detail.
Knowing which roach you have
Identification matters because different cockroaches behave differently in a building.
German cockroaches are small and light brown, and they live entirely indoors. They are the species most likely to spread from unit to unit through walls and plumbing, and the one most likely to need coordinated treatment.
Larger roaches, such as American and Oriental cockroaches, are more often found in basements, floor drains and damp lower levels. In a building they may point to a drain or basement issue rather than a neighbor’s kitchen.
A sticky trap placed under the sink for a few nights, or a clear photo of one roach, is often enough for a technician to tell which you are dealing with.
A close view of a German cockroach head and antennae. Knowing the species tells you whether the problem is likely to move through the building.
What tenants should do
- Report it to the landlord or building manager in writing, and keep a copy. A text or email with a date is better than a hallway conversation.
- Check your lease for anything it says about pest control, reporting, and access for treatment.
- Do not reach for retail sprays. They scatter roaches into the walls and into your neighbors’ units, which makes the building’s problem harder to fix.
- Reduce what roaches can use. Keep food sealed, take out trash nightly, wipe up grease, avoid leaving pet food out overnight, and report any leaks.
- Cooperate with treatment. Empty the cabinets under the sinks when asked, give access to the kitchen and bathroom, and leave bait placements alone.
What to tell the landlord
A clear report gets a faster, better response. Include:
- When and where you have seen roaches, including the rooms and the time of day
- Roughly how many, and whether any were small nymphs
- Any droppings, egg cases or odor you have noticed
- Photos, if you can get them
- Anything you have already done, such as fixing a leak or setting traps
- A request that the units next to, above and below yours be inspected as well
What landlords and building owners should do
For an owner, the goal is to treat the building’s problem rather than chase it from one unit to the next.
- Inspect beyond the complaint. Check the units on either side, above and below, along with shared basements, trash areas and laundry rooms.
- Treat connected units around the same time so roaches cannot simply move next door and wait.
- Tell tenants what to expect, including how to prepare and why they should not spray between visits.
- Fix the conditions. Repair plumbing leaks, deal with condensation, and close gaps around pipes under sinks and behind appliances.
- Keep records of complaints, inspections and treatments, which makes it easier to see whether a problem is spreading or shrinking.
If treatment is already underway and you are seeing small roaches again a week or two later, why German cockroach control takes more than one visit explains what is happening.
Stewart Termite & Pest Control has handled cockroach problems in Pittsburgh homes and apartments since 1987. Roach inspections are free and roach service carries a 90 day warranty. Call 412-822-7610 or request an inspection online.
Frequently Asked Questions
Can cockroaches come through the walls from the next apartment?
Yes. German cockroaches travel through gaps around pipes, wiring and outlets, and through the voids inside shared walls and plumbing chases that connect stacked units.
Why do roaches keep coming back after my apartment was treated?
The most common reason is a neighboring unit with its own population. Roaches keep arriving through shared walls and plumbing, so treatment works best when connected units are treated around the same time.
Who is responsible for treating roaches in a rental?
Check your lease for what it says about pest control and reporting. Either way, report the problem to your landlord in writing, keep a copy, and ask that neighboring units be inspected too.
I own a rowhouse. Should I tell my neighbors about roaches?
It is worth it. Rowhouses share walls, so a problem in one house can reach the next. Treating both homes around the same time gives each a better chance of staying clear.