How to get rid of cockroaches in a flat
Cockroaches are one of the few pests where the wrong response genuinely makes things worse. So it is worth being clear about what to do and, more importantly, what not to do.
What not to do
- Do not spray aerosols. This is the most common first step and the most damaging one. The aerosol kills the cockroaches you can see and scatters the rest: they flee deeper into the structure and into neighbouring flats. A few weeks later they come back, and the problem is now larger than it was.
- Do not rely on chalk and traps. Traps tell you that cockroaches are present and roughly how many, which is useful. They do not eliminate a colony.
- Do not put it off. Cockroach populations grow exponentially: one egg case holds 20-40 eggs and a female produces them regularly. A month of hesitation is a materially bigger problem.
What genuinely helps
- 1
Remove the water sources
Cockroaches do not survive long without water — far less long than without food. Fix dripping taps, wipe the sink and bath dry before bed, and do not leave water in the saucers under plant pots.
- 2
Reduce the food base
Food in airtight containers, crumbs out of cupboard corners, no dirty dishes left overnight, rubbish in a closed bin. This does not kill cockroaches, but it makes the bait far more attractive by comparison, which matters more than it sounds.
- 3
Seal the gaps
Around pipes, behind cupboards, at the ventilation openings. These are the routes from the neighbours.
- 4
Gel bait
The only method that acts on the whole colony, including individuals that never touch the bait themselves. See gel baits.
Why gel bait works and spraying does not
The mechanism is worth understanding, because it explains the whole approach.
A cockroach that eats gel bait returns to the harbourage before it dies. Other cockroaches feed on its droppings and its body, and pass the active substance on again. This cascade reaches individuals deep inside the structure that would never walk across a sprayed surface, including the nymphs that stay hidden in the harbourage entirely.
Spraying does the opposite. It creates a surface the cockroaches detect and avoid, so instead of concentrating them at a bait point it pushes them outward — into wall voids, up the riser, into the flat above. The colony is dispersed rather than reduced.
This is also why the two must not be combined carelessly. Spraying near bait placements contaminates them and the cockroaches stop feeding.
Why they come back in a block of flats
In Riga's Soviet-era system-built blocks cockroaches move freely between flats through the ventilation and pipe shafts. Treat one flat and the colony next door survives, and after a few weeks they are back.
This is also why cockroaches often appear immediately after the neighbours have had a treatment. They are not new arrivals from outside. They have simply relocated.
A durable solution is coordinated treatment of several flats and the shared areas, arranged through the apsaimniekotajs (the building manager) — see pest control for property managers. Per flat it usually costs less than repeated individual treatments, because the problem is solved once instead of being pushed around the building.
Realistic timings
With the gel method the number of cockroaches you see usually drops sharply within 3-7 days. Full elimination of the colony, including individuals hatching from egg cases, takes 2-4 weeks.
In the first days you may see more cockroaches than usual, including in daylight. They are coming out to the bait. It is a favourable sign, not a failure, and the worst thing you can do at that point is reach for a spray.
A treatment in a flat starts from €55 for one room, €60 for two and €65 for three. Gel bait needs no cupboards emptied and no leaving the flat, which is one of its main practical advantages.
Why they return after an apparently successful treatment
The situation where cockroaches disappear for a month and then come back almost always means one of three things, and none of them is the quality of the treatment.
- Continuous reinfestation from a neighbour. The colony next door was never touched and is topping yours up through the shaft. The pattern is a steady trickle rather than a sudden mass.
- A harbourage outside the treated zone. Most often the basement, the rubbish room or the stairwell — shared areas that are the building manager's responsibility, not yours.
- Reintroduction with goods. Cardboard boxes from a shop or a warehouse are a classic route, particularly for people who order a lot of deliveries.
Telling them apart matters, because the remedy differs. Fill in the form and describe the pattern: when they vanished, when they came back, and where you see them first. See also pests from neighbours.
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