Where can a rat squeeze through? - briefly
Rats can pass through openings as small as a quarter inch, roughly «6 mm», due to their flexible skeleton. Any gap of that size or larger—cracks, holes, vents, or pipe openings—provides a viable passage.
Where can a rat squeeze through? - in detail
Rats exploit gaps that are only a few centimeters wide. An adult Norway rat typically measures 20–25 cm in body length, with a head‑to‑tail length of about 30 cm when fully extended. The skeletal structure allows the skull and shoulders to pass through openings as narrow as 2 cm, while the flexible spine permits further compression.
Key passageways include:
- Wall cracks and mortar joints wider than 2 mm.
- Electrical conduit openings of 1–2 cm diameter.
- Drainage pipes with internal diameters of 3 cm or more, especially when the pipe is not fully filled with water.
- Ventilation grilles that have slats spaced at 1.5 cm or greater.
- Door sweeps and under‑door gaps exceeding 5 mm.
- Floorboard gaps or loose flooring tiles with separations of 2 cm or more.
- Chimney flues and fireplace openings that are not sealed, typically larger than 4 cm.
Structural features that facilitate rat entry:
- Insulation material that can be displaced, creating temporary voids.
- Unsealed utility penetrations where cables or pipes enter a building.
- Damaged or missing weather‑stripping around doors and windows.
- Exterior siding or cladding with loose panels or cracks.
Preventive measures focus on eliminating these apertures. Seal wall cracks with hydraulic cement, install metal mesh over vent openings, use steel wool or copper mesh in pipe gaps, and ensure door sweeps are intact. Regular inspection of the building envelope reduces the likelihood of rat infiltration.