The rat problem people describe on WhatsApp is almost always “there is a rat”. The rat problem we find is almost always a gap under a kitchen door, a bag of rice on the floor, and a drain running to a food shop two doors down. Getting rid of tikus is less about killing the animal in your house tonight and more about closing the route it used and removing the reason it came. Do it in the wrong order and you get the worst possible outcome: a dead rat sealed inside a ceiling you cannot open. This guide covers what actually works, in what order, and which of the popular fixes are a waste of your money.

Why one rat is never one rat

The arithmetic is the reason this is not a problem you get to postpone.

Gestation is about 22 days. A litter is commonly 5 to 8 pups. The young are breeding themselves at 3 to 5 months old, and in our climate there is no cold season to interrupt any of it — a female can produce up to about five litters in a year, and comes back into heat every few days. The three rats in Malaysian buildings are the Norway rat (Rattus norvegicus) in drains and at ground level, the roof rat (Rattus rattus) in ceilings, and the Asian house rat (Rattus tanezumi), which is extremely common indoors and routinely mistaken for the other two.

What that means in practice: a single sighting in January that nobody acts on is a family by March and a resident population with established routes by May. It also means the “just one rat, I’ll deal with it later” assessment is usually wrong at the moment it is made, because rats are neophobic — wary of new things — and you tend to see them only once the population is large enough that the confident ones are being pushed into the open.

The tell people miss. Droppings in more than one room means routes, not a wanderer. One rat produces a lot of droppings, but it produces them along its run. Droppings in the kitchen and the store room and the upstairs hallway is a different report entirely.

What works, in the order it works

Sequence matters more than product choice, and getting it backwards is what produces the smell in the ceiling.

1. Remove the food. Rice and pet food into sealed containers, bins closed, nothing left on the counter overnight, fruit off the table. This alone will not clear an infestation, but nothing else works properly while there is a buffet.
2. Trap and bait — indoors trap, outdoors bait. Snap traps set flush against walls where the droppings are, because rats run along edges rather than across open floor. Toxic bait in locked, numbered stations outside only.
3. Then seal. Only once activity has stopped. Sealing first is how you trap animals inside the structure.
4. Then monitor. Non-toxic blocks or monitors indoors, checked over a few weeks. A quiet fortnight is evidence; a quiet fortnight after sealing is proof.

People invert steps 2 and 3 constantly. It is an understandable instinct — the hole is the visible problem, so close the hole. But a rat that is inside when you close it does not leave; it dies somewhere unreachable, or it chews a new opening, which in a plaster ceiling takes it about an evening.

Why we never put poison in your ceiling

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Because of the delay. Anticoagulant rodenticides do not kill on contact or on the spot — they take roughly 4 days to 2 weeks of feeding to work, and in that time the rat carries on living its normal life. It dies where it feels safest, which is the deepest, warmest, most inaccessible part of its territory. In a Malaysian house that is the ceiling void, the wall cavity behind a built-in wardrobe, or the space above a plaster bulkhead.

Then you have a decomposition problem in tropical heat. The smell peaks over about a week and can take one to three weeks to fade, blowflies arrive and breed in the carcass, and the only reliable fix is finding it — which means cutting the ceiling open and paying someone to patch it afterwards. We have taken a genuine number of calls that started as “can you get rid of a smell” and ended as a carpentry job.

So the rule we work to, and the one you should ask any contractor about:

• Outside: toxic bait, in locked and numbered stations, tamper-resistant, positioned along runs and against the building.
• Inside: snap traps and non-toxic monitoring blocks. Traps hold the carcass where you can find it; monitors tell you whether anything is still moving through.

The loose blue pellets scattered in a roof space, which is what half the market still does, are the fastest way to convert a rat problem into a smell problem plus a rat problem.

Is rat poison dangerous to pets and wildlife?

Yes, and in two separate ways that are worth separating.

Direct. A dog that finds loose pellets eats them, because rodenticide is formulated to be attractive to a mammal. This is the argument for locked stations rather than trays, even outdoors.

Secondary. A cat, a monitor lizard or a bird of prey that eats a poisoned rat also takes in the anticoagulant, and it accumulates. Malaysian research on rodenticide use against the wood rat Rattus tiomanicus has examined exactly this risk to the barn owl, Tyto javanica javanica — a bird that Malaysian oil palm estates deliberately encourage with nest boxes precisely because it controls rodents for free. Poisoning the local owls to catch the rats they were already eating for you is a poor trade in a garden as well as a plantation.

None of this makes rodenticide unusable. It makes placement, containment and station discipline the difference between a professional job and a hazard.

What doesn’t work: ultrasonic, glue boards, cats

Ultrasonic plug-ins. Rodents hear ultrasound perfectly well and habituate to it within days, then carry on using the same routes with the device glowing in the socket. This is not a fringe opinion — the US Federal Trade Commission has brought enforcement actions against sellers of these devices and warned dozens of manufacturers that efficacy claims need scientific support. The plug-in also does nothing about the gap under the door, which is the actual variable.

Glue boards. They work reasonably on mice and badly on rats, which frequently pull free — leaving fur and skin on the board — or drag the whole thing somewhere you cannot reach. They are also indiscriminate: in a Malaysian house they catch cicak, the occasional bird, and sometimes a neighbour’s kitten. We do not use them as a primary method, and if a contractor’s entire plan is glue boards along a wall, that is a plan built around being cheap to deploy rather than likely to work.

The cat. A good mouser genuinely suppresses mice. Against a colony of Rattus tanezumi living in a ceiling void, an average house cat is a spectator with strong opinions. Some cats will not engage a full-grown rat at all, and the ones that do tend to bring the evidence to your pillow.

Peppermint oil, mothballs and chilli powder. Strong smells around a food source that a hungry animal has already committed to. At best they shift a route by a metre.

How do you actually seal a house against rats?

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By assuming the gap is smaller than you think it needs to be. A rat gets through roughly 20mm — about the width of a 50 sen coin — and a young one through less. It does not need to find a hole; it needs to find a weak edge it can widen, and rat incisors grow continuously and cut through plaster, timber, foam sealant and soft plastic without difficulty.

The gaps worth checking tonight:

• The gap under an external door, especially a kitchen or utility yard door with a worn threshold.
• Where water pipes, gas lines and air-conditioner drain lines pass through walls.
• Unscreened roof eaves and the joint where the roof meets the wall — the standard route for roof rats.
• Floor traps and drain outlets without a functioning grating.
• Air-well and utility yard openings, and the space behind a water heater or a built-in cabinet against an external wall.

What actually holds: steel wool packed into the gap and then sealed over, hardware cloth or fine metal mesh, cement mortar, and metal door sweeps. What does not: expanding foam on its own, silicone alone, cardboard, tape, and a plastic drain cover with a missing corner. Full detail on the routes is in how rats get into Malaysian houses.

A terrace house in Kepong called us about noise in the ceiling, and the owner had already put pellets in the roof space twice. There was no smell yet, which was luck rather than judgement. We took the pellets out, set traps along the run in the roof void, put two locked stations outside along the back drain, and told them not to seal anything for a fortnight. Caught three in the first week, nothing after that. The route turned out to be the eave above the kitchen extension — a 30mm gap where the new roof met the old wall. Mesh, mortar, done. The pellets had never been the problem or the solution; they were just a smell that had not happened yet.

— Job notes, Nomobug field team

What does a professional programme look like?

Unglamorous and mostly about record-keeping.

• A survey that maps the runs — droppings, smear marks along skirtings and pipes, gnaw damage, and the direction of travel. Smear marks are grease from the fur and they tell you which routes are in daily use.
• Numbered external stations, locked, positioned along the building line and the drain, mapped so every visit checks the same points.
• Internal traps and non-toxic monitors, placed on the runs rather than in the middle of rooms.
• Follow-up visits to check, reset and record. A rodent job without a second visit is a guess.
• Proofing recommendations in writing, priced separately, because the gaps belong to the building rather than to the treatment.
• A dated report per visit — essential for a business, and useful for a homeowner who wants to know whether activity is actually falling.

Two to four weeks is a realistic clearance window for a household infestation caught early. Where the food source is external and permanent — a restaurant row, a wet market, a construction site next door — the external stations stay in place as maintenance, because you are managing pressure from outside rather than eliminating a resident population.

What does it cost?