Why your condo isn't safe just because it's on the 20th floor
The most common thing we hear on a first visit: "But I'm on a high floor — how did they get in?" The answer is that in a Bangkok high-rise, cockroaches don't come through the window. They come through the building.
- Pipe shafts and risers connect every unit in the stack. A neighbor's infestation three floors down is your problem next month.
- Garbage rooms on each floor are a breeding reservoir — the roaches you see at night often commute from there.
- Deliveries and cardboard boxes carry egg cases straight past your front door's defenses.
- Drains — especially rarely-used floor drains in bathrooms — are an open highway when the water seal dries out.
The five habits that actually work
1. Keep the water seal in your floor drains
Pour a glass of water into every floor drain once a week. A dry trap is an open door — this one habit stops more roaches than any spray you can buy.
2. Break down boxes outside
Cardboard is both a taxi and a nursery for cockroaches. Break down delivery boxes and get them to the garbage room the same day — don't store them under the sink or on the balcony.
3. Starve the kitchen at night
Cockroaches are nocturnal and need surprisingly little: a few crumbs, a greasy stovetop, a pet bowl left out. Wipe surfaces after dinner, run the dishes, and lift pet food overnight.
4. Seal the gaps that matter
You don't need to caulk the whole unit. The gaps that matter are around pipes under the kitchen and bathroom sinks, and the gap under the front door. A ฿100 door sweep does more than a cabinet full of spray cans.
5. Treat the source, not the sighting
Supermarket spray kills the roach you see and scatters the colony you don't — often making things worse. Professional gel bait works the opposite way: the roach eats it, carries it home, and the colony collapses.
When to call a professional
One roach after a rainy night is Bangkok. Roaches every night, roaches during the day, or small brown German cockroaches in the kitchen mean an established colony — and colonies don't leave on their own.
A general pest treatment with documented gel bait placement typically brings activity to near zero within two weeks, and a quarterly plan keeps the building's pressure from re-establishing.
Frequently asked questions
How do cockroaches get into a condo on a high floor?
Through the building, not the window. Pipe shafts and risers connect every unit in the stack, garbage rooms on each floor act as breeding reservoirs, delivery boxes carry egg cases past your door, and rarely used bathroom floor drains become open highways once the water seal evaporates. A neighbour's infestation three floors down reaches you via these routes.
How often should I pour water down floor drains to keep cockroaches out?
Once a week. A glass of water into every floor drain, including guest bathrooms and the drain under the washing machine, keeps the U-trap water seal intact. In an air-conditioned Bangkok condo a trap can dry out within days of disuse and become an open door to the drain stack. This single habit stops more roaches than any spray.
Does supermarket cockroach spray make the problem worse?
Often, yes. Spray kills the roach you see and scatters the hidden colony into new harbourages, making the infestation harder to treat. Professional gel bait works the opposite way: the roach eats it, carries it back to the colony, and the colony collapses. Documented gel bait placement typically brings activity to near zero within two weeks.
When should I call pest control for cockroaches in my condo?
One large roach after a rainy night is normal Bangkok life. Roaches every night, roaches seen during the day, or small brown German cockroaches in the kitchen mean an established colony that will not leave on its own. PestsRova treats any pest at one flat price by unit size from ฿1,590 for a studio, with identification included free and 15% off the first visit.
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Written by the PestsRova Team
We're Bangkok's documented pest control crew — everything we write comes from real treatment visits across homes, condos and short-stay rentals.
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