What attracts cockroaches to a house

Warmth comes first

This is the one people underestimate. Cockroaches want somewhere warm to harbour, and modern kitchens are full of appliances producing steady low heat in enclosed spaces - the fridge motor housing, behind the dishwasher, under the oven.

That's why they establish in kitchens that are otherwise spotless. The cleaning happens on the surfaces; the harbourage is in the voids.

Then moisture

Cockroaches need water more urgently than food and can survive far longer without eating than without drinking. A leaking trap under a sink, condensation behind an appliance, or a floor drain that never fully dries will hold a population on its own.

Then food, and less of it than you'd think

The amount required is small. Crumbs under an appliance, grease behind a cooker, a pet bowl left down overnight, or an unsealed bag in a pantry is plenty.

Cardboard is worth calling out separately - it's both food and shelter, and boxes stored in a warm cupboard are close to purpose-built cockroach housing.

What to change

• Pull the fridge out and clean underneath and behind it - the single highest-value thing on this list
• Fix any leak under a sink, however minor
• Lift pet bowls overnight
• Move dry goods into sealed containers rather than original packaging
• Get cardboard storage out of warm cupboards
• Run kitchen and bathroom extraction properly

Where they come from in the first place

Often they arrive rather than appear. Deliveries, cardboard boxes, second-hand appliances and shared walls in flats are the usual routes. In a multi-unit building they move between units through service risers regardless of what any one household does.