Cockroaches in a Belgian home aren't a sign of poor hygiene. The insect travels in packaging, second-hand appliances, and between adjoining flats through the plumbing. How fast you react changes everything: a colony doubles every 6 to 12 weeks.
The species that dominates in Belgium
The German cockroach (Blattella germanica) is the most common species in Belgian homes. Small (10–15 mm), it prefers warm (25–30°C), humid environments: kitchens, electrical meter boxes, heated false ceilings, shower drains.
The Oriental cockroach (Blatta orientalis) is larger (20–25 mm) and tolerates cold and damp better. Found in cellars, crawl spaces and drains, more rarely in flats but common in older buildings and basements.
Identifying the species before treating isn't a formality: insecticides effective on the German cockroach don't work the same way on the Oriental cockroach, and their target habitats differ.
Understanding the reproduction rate
A female German cockroach produces 4 to 8 egg cases over her lifetime. Each egg case holds 30 to 40 eggs. Under favourable conditions, a single female can theoretically generate up to 320 direct offspring.
The full cycle, from egg to a reproducing adult, takes 6 to 12 weeks depending on temperature. A flat at 25°C (central heating) creates ideal conditions for closely spaced generations.
An adult survives 1 month without food and withstands high levels of environmental stress. Seeing cockroaches in broad daylight is a clear sign of a massive infestation: the colony then often exceeds 50 individuals, and the available hiding spots are no longer enough.
The insecticide resistance problem
The German cockroach has developed resistance to common insecticides from the pyrethroid family, the same molecules found in supermarket aerosol sprays. A DIY treatment with these products scatters the colony to other rooms or to the neighbours, without eliminating it.
Urban populations are particularly resistant due to accumulated selection pressure. An effective professional treatment combines different active products with targeted application in hiding spots, the opposite of a surface spray that scatters the colony instead of treating it.
Documented health risks
Cockroaches are mechanical vectors: they carry bacteria picked up in drains and waste on their legs and cuticle, including Salmonella, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa, as well as intestinal parasite eggs. Their shed skins and droppings are also recognised allergens, implicated in asthma and rhinitis in infested homes.
For food businesses, HORECA and food retail in Belgium, a cockroach presence risks immediate closure by the FASFC. The HACCP protocol requires a documented pest control plan: the professional intervention report is a mandatory document during an inspection.
In a building, cockroaches move between flats through plumbing risers and false ceilings. An untreated infestation eventually reaches neighbouring homes: that's why an isolated treatment rarely gives lasting results in a multi-unit building.
What we actually do
Professional treatment always starts with an inspection: identifying the species, locating the main hotspots and assessing the infestation level. This step shapes everything that follows.
Next comes targeted treatment in the identified hiding spots, followed by a check to confirm the population isn't rebounding. In an adjoining building, coordinated treatment of the whole plumbing riser prevents reinfestation from neighbours.
You don't need to prepare a protocol or identify the species yourself: the technician handles that on site and explains what they're doing before starting.
Frequently asked questions
Do I need to leave my flat during treatment?
Generally not for a standard treatment: products are applied at targeted points, with no airborne diffusion. The technician tells you if a short absence is needed depending on the method used.
Why do cockroaches come back after treatment?
Two main causes: eggs not yet hatched at the first visit (hence the follow-up check) and reinfestation from neighbouring flats. In a building, treating a single unit often fails if the neighbours don't treat at the same time.
How long does it take to get rid of cockroaches?
Results are judged over a few weeks, the time it takes for treatment to work through the whole colony. A follow-up check confirms activity has genuinely stopped.