Almost every cockroach problem we are called to has the same shape: a spray from the supermarket kills the ones you can see, and two weeks later the kitchen is busy again. That happens because the insects you see are a small fraction of the population — the rest are behind the slab, inside the hinge cavity of the modular kitchen, under the sink and in the motor housing of the fridge.
Getting rid of them means treating where they live and breed, not where they walk. That is the difference between a surface spray and a gel bait programme.
Where cockroaches actually hide
- Hinge cavities and corner joints of modular kitchen units
- Behind and underneath the sink, especially around the waste pipe
- The warm motor housing at the back and base of the refrigerator
- Gaps behind the gas platform, chimney duct and microwave shelf
- Bathroom floor traps, pipe sleeves and the cavity behind WC cisterns
- Cardboard cartons and paper bags stored under the sink or in lofts
Why sprays fail and gel baiting works
A contact spray only kills the insects it lands on, and it leaves a residue that live cockroaches then avoid — so the surviving population moves deeper into the cavity and keeps breeding. Fumes also mean you have to vacate the kitchen.
Gel bait works the other way around. A pea-sized dot placed inside the harbourage is eaten and carried back into the colony, so the insects that never come out are still affected. It is odourless, applied inside cabinets rather than on open surfaces, and the kitchen stays usable the same day.
What you can do before the technician arrives
- Empty and wipe the under-sink cabinet so bait can be placed inside it
- Take out cardboard cartons, old newspapers and paper bags
- Fix a dripping tap or leaking waste pipe — cockroaches need water more than food
- Cover the kitchen bin and empty it at night rather than in the morning
- Do not spray anything in the week before treatment; it pushes the insects out of reach of the bait
How long a proper treatment takes to work
Activity usually rises for the first two or three days as insects leave the harbourage to feed on the bait, then drops sharply through the first week. A heavy German cockroach infestation in a restaurant or a shared building shaft normally needs a follow-up visit two to three weeks later to catch the generation that hatched after the first round.
If the building has a common garbage chute or a neighbouring flat with the same problem, expect re-entry through the shaft and plan a periodic schedule rather than a one-off visit.
Frequently asked questions
Do we have to empty the entire kitchen?
No. Gel baiting only needs the under-sink cabinet and any cluttered drawer cleared. Utensils, groceries and appliances can stay where they are.
Is cockroach gel safe around children and pets?
The gel is placed as small dots inside cabinet cavities, hinge gaps and pipe sleeves — not on open surfaces or the floor — so it stays out of reach. Tell the technician if you have a crawling baby or a cat so placement can be adjusted.
Why did cockroaches come back after two months?
Usually re-entry rather than treatment failure: a shared drainage shaft, a common garbage chute or an untreated neighbouring flat. In buildings like that a periodic schedule works better than a single visit.