How Exterminators Know if Roaches Are in Walls

Your instinct is getting you to want to know if roaches are in walls. Fortunately, it’s even easier to identify evidence of a roach, compared to finding the insect itself.

Cockroaches are nocturnal—they operate at night but during the day, they stay hidden in cracks and crevices.

Of course, the roaches are attracted to every food and chunk in your home or workspace. The average cockroach eats anything from paper, food, fabric, and plastics, to name a few. If you think there are roaches in the walls, this publication covers every exterminator’s tips to tell if there are cockroaches in there.

How to Know if Roaches Are in Walls

How to Know if Roaches Are in Walls

Look for the following signs to know if there are cockroaches in your walls:

1. Smear marks

Roaches usually produce dark, irregular-shaped smear marks in moist areas of walls as they crawl along or while resting. The marks can be spotted at your wall-floor junctions and horizontal surfaces where the roaches are present.

The point is that roaches will produce brown and irregularly shaped smear marks if the area around the wall is excessively moist.

2. Roach droppings

If roaches are in walls, you should find black droppings, typically less than 1mm wide and of varying lengths and sizes. The droppings are similar to ground coffee or black pepper.

If you find the droppings, you need to cautiously clean them up. The droppings contain certain proteins known as allergens, present in roach feces, saliva, and body parts, according to the National Pest Management Association. This can cause allergic reactions or trigger asthma symptoms, especially in children, and can easily spread through physical contact.

3. Shed skin

If you find any evidence of shed skin on walls, roaches could be sheltering there. Roaches typically shed nymphal skins about 5-8 times as they grow In size through different lifecycle stages into adulthood. The shed skins vary in size, so look for them on walls.

4. Physical damage

Any unusual sign of tiny damage around the wall could be a sign to know there are roaches lurking around. Apart from food packaging, a roach will also eat organic goods such as books and leather.

5. Oily, musty smell

If there are roaches on your wall, you should perceive a lingering, unpleasant and oily, musty smell.

Roaches tend to leave feces behind where they nest. The droppings will produce a pheromone, which attracts more roaches to the area. The pheromone does not only linger as cockroach infestation grows but will also taint walls and lure in more roaches.

6. Egg capsules

A cockroach lays eggs in a capsule, also called oothecae, which contains multiple eggs, and this capsule is unique according to the cockroach specie. For example, a German cockroach ootheca contains up to 18 segments, while a brown-banded cockroach only has about 8 segments. However, American and Oriental, and American cockroach oothecae feature no clear segmentation but have circular, raised areas beneath the keel.

Read also: will stepping on a roach kill it?

Some roach species leave the ootheca behind immediately. However, the German cockroach moves around with it until it is closer to hatching. After hatching, about 30 tiny nymphs are released.

How to remove roaches from walls

If you have a cockroach infestation in the walls, follow the steps below to properly exterminate them:

a) Get rid of their water sources

Start the elimination process by cutting off water sources to the walls. Cockroaches can survive for about 2 months without food but they frequently need water to survive. This is the reason you need to repair pipe leaks and clean up standing water pools to cut off the moisture in the wall roaches rely on to infest.

b) Eliminate food sources

You want to remove all food sources in the wall and your home as a whole. Consider the following:

  • Do not leave dirty dishes in your sink.
  • Remove food or crumbs on countertops.
  • Sweep or vacuum after cooking.
  • Store leftover food in airtight containers.

These basic practices block the food sources the roaches depend on to feed and nest in walls.

c) Declutter your home or workspace

Declutter around the house. Take out unused plastic/paper bags, newspaper piles, empty boxes, and other messy piles. Disposing of the clutter does not only eliminate roach hideouts near walls but also makes your space neater and spacious.

d) Block possible openings leading inside

You need to deny roaches further access to the house by sealing pipe gaps with flexible caulk. Patch all wall cracks and crevices as well to prevent roaches from squirming through them inside the house.

e) Get an insecticide

There are various long-term cockroach insecticides you can buy from your local or online store. A spray insecticide will only kill the cockroaches you see, and not the ones still hiding in walls. Spray insecticides will not control a full-blown roach infestation, so there’ll still be a number of them lurking around.

Read also: there could be more if you found one bed bug

To fully control cockroaches in walls, get an insecticide that targets roaches at their source. Roaches will readily ingest the baits and gels, and take them to their wall hideouts, where the poison spreads to the rest of the nest through their sputum, feces, and carcasses.

Where cockroaches live apart from just walls

The location of a cockroach infestation depends greatly on the species in your home. While some prefer cooler conditions, others tolerate warm and humid areas. Look for roaches in the following places:


The kitchen is home to roaches, especially inside cracks. If you have chunks and dirty dishes in your kitchen, roaches will pay you a visit.

However, you should find them lurking around in cupboards and cabinets. Roaches prefer the darkness, especially when there are pipes in the cabinet.

Loom out for roaches in your appliances such as dishwasher and cooker where cockroaches may nest for warmth.


Roaches can nest in the walls of the bathroom. Look at the back cabinet joints where roaches could be snacking on toilet paper, soap residue, and tissues.

The plumbing behind sinks, showers, toilets, and bathtubs are sheltered dark spaces with water access, creating the needed moisture for roaches.

Laundry rooms

Inspect your cabinets for cockroach infestation. Any form of moisture will attract roaches.

Your washer/dryer is another place in the laundry room to find roaches. The motor creates the needed warmth attracting cockroaches.


Your cracked pipe ducts leave enough room for roaches to get inside.

Also, check your drain covers for damage.  Roaches fit through small spaces, thus an insignificant defect is enough for roaches to leverage their way into the house.


Cockroaches hide in small areas such as cracks or gaps in baseboards. Make sure to also check your wall bases and corner joints for small holes providing free entry for roaches. Stored cardboard or paper can also serve as a roach nest—they can eat and hide in these materials.


Knowing if roaches are in walls is one thing but eradicating them is another. If cockroaches get a foothold in your walls, it can be challenging to remove them but not impossible.

If you have a large roach infestation, you may need professional cockroach control. Remember, apart from appearing eerie, roaches also spread illness and exacerbate asthma issues. Contact an exterminator specialist to treat the roach infestation source and prevent them from returning.

Exclusive: bay leaves as roach repellent explained

Leave a Reply