How do rodents get into a house?
A mouse fits through a gap the size of a small coin, a rat through one the size of your thumb. Control starts by closing the route, not by setting the trap.
Most people who call us about rodents ask which poison we use. The more useful question is where they are getting in, because setting traps in a property whose entry points are still open just means swapping one rodent for another every couple of weeks.
How small a gap actually needs to be
A rodent's skeleton is flexible and its skull is narrower than it looks. In practice:
- A mouse passes through a hole around fifteen millimetres across.
- A rat needs roughly double that.
- Both will gnaw wood, plastic and insulation to widen something smaller.
Which is why "there are no holes in my house" is true to the eye and false to a tape measure.
The five most common ways in
- Around pipework. The gap between a drain or water pipe and the wall it passes through, especially under kitchens and bathrooms.
- Under external doors. A two centimetre gap between door and threshold is entirely enough.
- Air conditioning and ventilation openings that have no wire mesh over them.
- Electrical and data entries where a wall was drilled and never sealed around the cable.
- Inspection chambers and drain covers that are cracked or do not seat properly.
What attracts them in the first place
Rodents are not exploring. They want three things: water, food and somewhere warm to nest. Remove any one of them and the property gets much less appealing.
An open rubbish bag behind the door is a standing invitation, however good the treatment was.
Pay particular attention to pet food left out overnight, open bags of rice and flour, and standing water under an air conditioning unit or behind a washing machine.
Signs before you ever see one
- Small dark droppings shaped like a grain of rice, usually behind appliances or inside low cupboards.
- Gnaw marks on the edges of boxes, bags or cabling.
- Dark greasy smears along walls near floor level, because they travel pressed against the wall.
- Scratching or running sounds inside a false ceiling or a wall cavity at night.
Why poison alone is not the answer
Serious control is three steps in this order: seal the entry points, then remove the food and water, then traps and materials placed deliberately and well away from children and pets. Starting at step three is why the problem keeps coming back for most people who treat it themselves.
There is also a practical reason to avoid poison alone indoors: a rodent may die inside a wall or ceiling void, and a rodent problem becomes an odour problem that is very hard to reach.