Cockroaches don’t climb 15 storeys of bare wall to reach your kitchen. They ride the building’s own plumbing and rubbish chutes. The single most important thing to understand about a high-floor condo is this: a German cockroach colony can spread from one unit to the units directly above and below within a few weeks through a shared plumbing riser — which means your floor number gives you almost no protection. People assume the 18th floor is too high for lipas. The lipas were never coming from the ground.

How They Actually Reach a High-Floor Unit

There’s a comfortable myth that high-rise living puts you above the pest problem. It doesn’t. A 30-storey tower is not 30 separate houses stacked up — it’s one structure threaded top to bottom with continuous vertical channels, and every one of those channels is a corridor a cockroach can walk.

Think about what runs the full height of your building without a break: the kitchen and bathroom plumbing stacks, the electrical and data risers, and the rubbish chute. All of them are dark, warm, slightly humid, and in the case of the chute, smell permanently of food. That is close to a cockroach’s idea of a perfect highway. They move up and down it and slip into individual units through the gaps where pipes and cables pass through the wall.

And then there’s the shortcut almost nobody counts: the lift, the staircase, and your own grocery bags. A German cockroach hitchhiking in a cardboard box from the supermarket doesn’t care that you live on the 22nd floor. It rode the lift up with you.

Two Species, Two Very Different Routes

Which cockroach you’re seeing tells you exactly how it got in. Two species turn up in KL apartments, and they take completely different roads.

• The German cockroach — small, light tan, about the length of your thumbnail, the ones that scatter when you switch the kitchen light on. This species lives indoors and breeds indoors. It rarely comes up from the drain. It arrives inside something — a grocery box, a used microwave, a delivered parcel — or it walks across from a neighbouring unit through the shared kitchen wall. One female carries an egg case holding 30 to 40 young, so a couple of hitchhikers become a cabinet full in a month or two.
• The American cockroach — big, reddish-brown, the one that occasionally flies and makes everyone in the room stand on a chair. This one comes up from the wet world: storm drains, sewer lines, the bathroom floor trap. In a high-rise it travels up the plumbing stack and emerges through a floor trap whose water seal has dried out.

This matters because the fix is different for each. If you’re not sure which one you have, the German vs American cockroach guide has a 30-second test. One important biology note while we’re here: cockroaches have no queen and no organised nest the way ants or termites do. They simply gather wherever it’s warm, dark and tight — behind a cabinet hinge, under the fridge motor — which is why you treat the harbourage, not a single central point.

The Building Itself Works Against You

Here are the parts of a condo that quietly help cockroaches, none of which you’ll find on the floor plan the developer showed you:

• Boxed-in plumbing risers. The pipework behind your kitchen and bathroom cabinets is shared with the unit above and below. The gaps where it passes through the slab are rarely sealed. A German cockroach flattens to pass through a gap about 1.5mm wide — the edge of a coin — so those gaps are open doors.
• The rubbish chute. A vertical food-scented tunnel running the height of the block, with a hopper door on every floor. If the doors don’t seal or the chute isn’t cleaned, it breeds and distributes cockroaches to every level at once.
• False ceilings and service ducts. The void above your bathroom ceiling often connects to the common corridor and the next unit. Cockroaches travel it unseen.
• Bin rooms and the basement. Ground-level rubbish collection and wet basement car parks are where American cockroaches breed before heading up the stacks.

The point isn’t that your building is badly built. Most aren’t. It’s that an apartment is a connected system, and a pest problem in a connected system is never fully a single-unit problem. The German cockroach allergens these colonies produce are also a known asthma trigger, which the Ministry of Health flags in its environmental health guidance — one more reason not to let a chute-fed colony settle in.

Why Treating Only Your Unit Doesn’t Hold

This is the part most people learn the expensive way. You bait your unit, it goes quiet for two or three weeks, and then they’re back — and you assume the treatment failed. It didn’t. The colony in the shared riser or the untreated unit next door simply pushed new arrivals through once the first wave was gone.

A clean, well-kept unit sitting next to a problem unit will keep getting visitors no matter what you do inside your own four walls. That’s not a knock on your housekeeping. It’s just plumbing.

“I rented an apartment beside waste chamber, for 2 years being spraying consistently but to no avail. But this service clear the root problem by give bait to main points around the house so that even the little ones baited.”

— Afiq Zamanhuri. Two years of spraying an apartment next to the waste chamber, no result. The location was the problem, not the cleaning — and baiting the right points is what finally settled it.

A recent job in a Cheras condo — 12th floor, customer had been told for years that high floors don’t get lipas. Small German cockroaches behind the kitchen cabinet, getting worse every month. We traced it to an unsealed gap around the sink waste pipe shared with the stack. Baited the harbourage, sealed the pipe gap, and flagged it for the management because two units below had the same thing. Their floor never mattered. The riser did.

— Job notes, Nomobug field team

This is also why cockroaches keep coming back after spraying in apartments specifically — spray clears the surface you can see and never touches the source feeding the unit. And it’s the same reason a spotless condo can still have a cockroach problem: the variables that matter are mostly outside your unit.

What Actually Keeps Them Out

You can’t reseal the whole building, but you can shut your unit’s doors and treat what’s inside. The order matters.

Seal your side of the shared paths

• Pack steel wool or sealant into the gaps where pipes and cables pass through the wall under the kitchen sink and behind the cabinets.
• Screen every floor trap with a stainless mesh cover — about RM10 each, and it blocks most American cockroach visits from the stack.
• Run water down every drain weekly, especially in a guest bathroom or laundry area you rarely use. A dry U-bend is an open pipe straight from the riser.
• Check the seal on your rubbish chute hopper door if your unit has one on the wall.

Treat what’s already inside

• Provecta gel bait (BASF’s professional, family-safe range) placed as pea-sized dots in the harbourage — inside cabinet hinges, behind the fridge, under the stove. No spray near the bait; the smell ruins it and just scatters the colony.
• Three short visits over 14 days — day 0, day 7, day 14 — to catch new young as they hatch. No need to move out for any of it.

One thing after treatment: don’t mop or wash along the wall edges for a couple of weeks. That strip is exactly where the residual sits, on the insect travel paths, and mopping it off resets the job. Specifically, leave these three zones alone: the floor along the inside of walls, the kitchen floor strip closest to the walls, and the floor along the outside walls. The middle of the room is fine to mop as normal — only the wall-adjacent edge is off-limits.

For a condo where several units are affected, the only durable fix is a building-wide treatment co-ordinated through management — every unit on the stack on the same day, so there’s no untreated neighbour left to restart it. Nomobug’s general pest control runs the 3x plan at RM499 with a written warranty, and we’ll talk to your JMB or building manager if a block-wide job makes more sense than one unit at a time.