Cockroaches in Your Toronto or Scarborough Apartment: A Tenant's Guide

Quick answer: If you’ve seen one cockroach in a Toronto or Scarborough apartment, you have a building problem, not a unit problem. German cockroaches travel between units through shared walls, plumbing chases and hallways, so treating a single apartment while the neighbours go untreated almost always fails. Report it to your landlord in writing, prepare your unit properly for treatment, and push for a building-wide inspection. Sani IQ handles multi-unit cockroach programs across the GTA — (705) 302-1887.

Finding a cockroach in your apartment is unsettling, and the advice you get is usually contradictory. Some people tell you to bomb the place. Some tell you it’s the landlord’s problem and you should do nothing. Some tell you to move.

This guide is the practical version: how to confirm what you’re dealing with, what happens next, and what you can actually do that makes a difference. If your question is specifically about who has to pay, we’ve covered the legal side separately in who pays for pest control: landlord or tenant in Ontario — this piece is about the pest itself and the treatment.

Almost certainly, it’s a German cockroach

Ontario has several cockroach species, but in apartments it’s overwhelmingly one: the German cockroach. Knowing that matters, because it explains everything about why these infestations behave the way they do.

What it looks like. Small — 12 to 16 mm as an adult, roughly the length of your thumbnail. Light tan to brown, with two dark parallel stripes running lengthwise down the shield behind the head. Nymphs are much smaller and nearly black with a pale stripe, and they’re often mistaken for a different insect entirely.

Why it’s the hard one. German cockroaches are the fastest-breeding cockroach in Ontario homes. A single female carries her egg case until just before hatching — which protects it from most sprays — and each case holds roughly 30 to 40 eggs. In a heated apartment there’s no seasonal slowdown. That’s why an infestation that was invisible in April can be obvious by August. Full identification details are in our German cockroach guide, and our complete Ontario cockroach field guide covers the other species you might be looking at.

The signs, in the order you’ll notice them

A cockroach in daylight. German cockroaches are nocturnal and hide by preference. Seeing one during the day means the harbourages are crowded — a population indicator, not a chance encounter. This is the single most important sign in this list.

Droppings. Look like coarse black pepper or coffee grounds, accumulating in corners of cupboards, along the tops of doorframes, behind the kitchen sink, and in the hinge recesses of cabinet doors. In heavier infestations you’ll see dark smear marks in humid areas.

Egg cases. Small, tan, ridged capsules about 8 mm long, purse-shaped. Found in cracks, behind drawers, under sinks.

Shed skins. Cockroaches moult several times as they grow, leaving pale, hollow, papery casings that look like a translucent cockroach.

A smell. Established infestations produce a distinctive musty, oily odour. If you can smell it, the population is substantial.

Where to look. Take a flashlight and check: under and behind the kitchen sink, the motor compartment and door gasket of the fridge, inside and under the dishwasher, the gap between counter and wall, cabinet hinge recesses and corners, around and behind the stove, the bathroom vanity and around plumbing penetrations. German cockroaches want warmth, moisture and a tight crack — the kitchen and bathroom are where they will be.

Why one-unit spraying doesn’t work

This is the part that frustrates tenants most, and the reason is structural.

German cockroaches move between apartments continuously. Shared wall voids, plumbing chases around stacked kitchens and bathrooms, electrical conduit, and gaps around baseboards and under doors all function as highways. A unit that gets treated while the units above, below and beside it don’t is simply re-invaded within weeks. The tenant concludes the exterminator was useless. The exterminator did their job; the scope was wrong.

Worse, over-the-counter aerosol foggers actively make things worse in a multi-unit building. Foggers don’t reach into the cracks where cockroaches live, but they do repel — the population disperses deeper into wall voids and into neighbouring units, turning one unit’s problem into three. If there is one thing to take from this guide: do not use a bug bomb in an apartment.

What does work in multi-residential settings is a coordinated program: inspection of the affected unit and every adjacent one (beside, above and below at minimum), gel bait applied into harbourage points rather than sprayed across surfaces, follow-up visits timed to catch the nymphs hatching from egg cases that survived the first round, and monitoring to confirm the population has actually collapsed rather than moved. We wrote about the same dynamic in townhomes and condos in our Markham German cockroach guide.

How to prepare your unit for treatment

Preparation is the part tenants control, and it materially changes the outcome. Most failed treatments in apartments involve a unit that wasn’t prepped.

Do this before the technician arrives:

• Empty kitchen cabinets and drawers where activity has been seen, and wipe out droppings and debris. Bag contents and set them in the middle of the room.
• Clean thoroughly under and behind the stove and fridge — pull them out if you can. Grease and crumbs behind appliances are the main food source.
• Clear the space under both sinks completely.
• Fix or report dripping taps and leaks. Cockroaches can survive weeks without food but not without water, and a slow leak under a sink will sustain a population through any bait program.
• Remove cardboard. Cardboard boxes and paper bags stored in the kitchen are ideal harbourage and a common source of the original introduction.
• Do not spray anything yourself in the days before treatment. Residual retail insecticide on surfaces repels cockroaches away from the gel bait the technician places, which is exactly what you don’t want.

After treatment:

• Do not wash down the areas where bait was placed. Bait needs to stay available for weeks.
• Expect to see more cockroaches for the first several days, including in the open. That’s the bait working and the population being flushed out of harbourage — it is not a sign of failure.
• Keep every follow-up appointment. Egg cases that were shielded during the first visit hatch on their own schedule, and the follow-up is what catches that generation. Skipping it is the most common way a program that was working gets abandoned halfway.

Reporting it: put it in writing

Even setting the legal detail aside, a written record changes how these situations resolve. Email or message your landlord or property manager rather than mentioning it in person, and include the date you first saw activity, where in the unit, roughly how many and whether any were in daylight, and photos if you have them. Ask directly whether neighbouring units are being inspected — that single question is often what converts a one-unit callout into a proper building-wide response.

Keep copies of everything. If the response stalls, that record is what you’ll need.

For property managers and building owners

If you manage buildings in Toronto, Scarborough or Etobicoke, the arithmetic on German cockroaches is straightforward and it does not favour reactive, unit-by-unit response.

Treating complaints one unit at a time means paying for repeated callouts on a population that is never actually eliminated, while it spreads laterally through the stack. It also generates the paper trail that leads to municipal enforcement — Toronto’s apartment building standards program has timelines attached, and a pattern of unresolved unit-by-unit complaints in one building draws attention.

A block program — inspecting and treating an affected unit together with its neighbours in the same stack, on a scheduled follow-up cycle — costs less per unit than the callout treadmill and actually ends the infestation. Our commercial pest elimination service covers multi-unit residential, and we’ll scope a building rather than a door. For a sense of what cockroach work costs in this market, our Toronto cockroach exterminator cost guide breaks it down, and the cockroach exterminator Toronto page covers same-day service.

Call (705) 302-1887 for a building assessment.

Frequently asked questions

I’ve only seen one cockroach. Is that really an infestation? Almost always, yes — particularly if you saw it during the day. German cockroaches are nocturnal and hide by preference, so a visible one implies a population large enough that harbourages are crowded. The reproductive maths compounds it: a single female’s egg case holds 30 to 40 eggs, and in a heated apartment breeding doesn’t pause seasonally.

Should I use a bug bomb or fogger while I wait? No. Foggers don’t penetrate the cracks where German cockroaches actually live, but they do repel — the population scatters deeper into wall voids and into neighbouring units. You end up with a larger, more dispersed problem and a unit contaminated with residual repellent that will interfere with the gel bait a technician needs to place.

Does having cockroaches mean my apartment is dirty? No. In multi-unit buildings, cockroaches arrive through shared walls, plumbing chases and hallways, or in delivered packaging, entirely independently of how a unit is kept. A spotless apartment beside an infested one gets cockroaches. Cleanliness affects how fast a population grows once it’s there, not whether it arrives.

How long does treatment take to work? Expect a program of several weeks with multiple visits rather than a single treatment. Gel bait works through the population over days, and follow-ups are timed to catch nymphs hatching from egg cases that survived the first round. Activity typically increases for the first few days, then drops sharply.

Can cockroaches make you sick? They’re a recognised trigger for asthma and allergic reactions, particularly in children — the allergens come from droppings, shed skins and body fragments accumulating in dust. They also mechanically carry bacteria across surfaces from the areas they forage in. This is the main reason apartment infestations shouldn’t be left to run.

My landlord treated my unit twice and they came back. What now? That pattern is the signature of a scope problem, not a treatment problem. Ask in writing whether the units beside, above and below yours have been inspected and treated on the same schedule. Until adjacent units are handled together, your unit will keep being re-invaded no matter how many times it’s treated on its own.