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Cockroaches In A Flat
Small brown insects running from the light behind the kitchen units, and a musty smell in the cupboards.
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What's happening?
Two species matter in UK homes. German cockroaches are small, pale brown with two dark stripes behind the head, cannot survive outdoors here, and live permanently indoors in warm humid voids — behind fridges, inside kitchen units, around a boiler, in a bin store. Oriental cockroaches are larger, darker and more associated with drains, basements and communal areas. Both are nocturnal, so seeing one in daylight generally means the population is already substantial. The critical fact about flats is that cockroaches do not respect a front door: they move through service voids, riser cupboards, waste pipes and shared walls. Treating one flat while the neighbouring flat and the communal areas are untreated does not clear the block — it just moves the population around.
What usually causes it?
- Warm, humid voids indoors — behind and beneath appliances, in unit runs, around a boiler or riser
- Spread through shared walls, service voids, riser cupboards and waste pipework in a block
- Communal bin stores and refuse chutes acting as a reservoir for the whole building
- Brought in on cardboard, deliveries, second-hand appliances or luggage
- Food debris and grease behind and under appliances and inside unit carcasses
- Dripping pipes and standing water under sinks providing the moisture they need
- Cardboard, paper and clutter stored in warm cupboards, giving harbourage and egg-laying sites
Is it dangerous?
Yes, this is one to act on rather than tolerate. Cockroaches move between drains, refuse and food surfaces and are associated with the spread of organisms causing food poisoning; their droppings and shed skins are also a recognised trigger for asthma and allergic reaction, particularly in children. Insecticide sprayed by an occupant makes things measurably worse — repellent products scatter German cockroaches into adjacent voids and flats, and resistance to some amateur products is well established.
Can I fix it myself?
The conditions, not the treatment. Clean thoroughly behind and beneath the cooker, fridge and units, fix leaks and dry out under-sink cupboards, remove cardboard and clutter from warm cupboards, and store food in sealed containers. Empty bins nightly. Keep any sightings, with dates and locations, because that record is what gets a block-wide treatment organised. Do not use aerosol sprays or foggers on German cockroaches — you will spread them — and do not seal voids before treatment, which traps the population inside.
When should you call a pest controller?
Call a pest controller straight away, and in a flat report it in writing to the landlord or managing agent at the same time. This is a professional treatment: species identification, gel bait and insect growth regulators placed in harbourage, and repeat visits through the life cycle. Tell the agent that adjoining flats and the communal areas need inspecting — and if nothing happens, your council's environmental health team has powers, both over landlords and where a pest problem amounts to a statutory nuisance.
What will the pest controller actually do?
- Identify the species, because German and Oriental cockroaches need different treatment and different search areas
- Inspect harbourage — behind appliances, inside unit carcasses, riser cupboards, drains and bin stores
- Place gel baits and insect growth regulators in harbourage rather than spraying open surfaces
- Set monitors to measure the population and confirm whether the treatment is working
- Return through the life cycle, since eggs are not killed by the initial treatment
- Advise the managing agent on the adjoining flats, service voids and communal areas that must be treated together
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