07/10/2026
The biro pen test for mice 👇
How small is the gap a mouse needs to enter your home?
A young mouse can squeeze through an opening just 6mm wide. That is roughly the width of a standard biro pen.
As the weather starts to cool, mice (and rats) will seek warmth, shelter and access to food and water. Small gaps around your property act as open doors.
Check your air bricks, as unprotected air vents are one of the most common entry points into floor voids.
Do you have any small gaps where outdoor taps, boiler pipes, or waste lines pass through brickwork? They are also common access points.
When it comes to front, back, or garage doors, any worn rubber seals or gaps under timber can also be used by rodents.
Prevention is always better than cure, for more information email [email protected]