How Big of a Hole Can a Rat Get Through?

Rats are surprisingly good at squeezing through tight spaces. A gap beneath a door, an opening around a waste pipe or a damaged air brick may be all they need to find their way into a property.

One of the most common questions homeowners ask is just how small an opening needs to be before a rat can get through. The answer depends on the size of the rat, but the gap can be considerably smaller than you might expect.

How Small a Hole Can a Rat Squeeze Through?

An adult rat may be able to squeeze through an opening approximately 20 mm (about three-quarters of an inch) wide, although larger rats may need more room. Young rats can sometimes pass through smaller gaps.

Rats have flexible bodies, but their skulls cannot compress in the same way. If the head can fit through an opening, the rest of the body may be able to follow.

This is why even relatively small gaps around pipes, doors and damaged brickwork deserve attention. Rats can also gnaw at certain materials to enlarge an existing opening.

How Big Are Rat Burrow Holes?

Rat burrows are usually much larger than the gaps rats use to enter buildings. A typical rat burrow entrance is approximately 5–10 cm (2–4 inches) across, although the size can vary.

Burrows are commonly found beneath sheds, alongside foundations, under vegetation and near garden boundaries. Freshly disturbed soil around an entrance can suggest recent digging activity.

Not every hole in the garden belongs to a rat, however. Other animals can create similar openings, so it is important to look for additional evidence before identifying the cause.

Where Do Rats Commonly Enter Houses?

Rats often take advantage of existing weaknesses in a building rather than creating an entirely new opening.

Some of the places worth checking include:

• Around pipework: Gaps where water, gas or waste pipes pass through external walls.

• Beneath doors: Damaged door seals or poorly fitting garage doors.

• Air bricks and vents: Broken covers or missing protective mesh.

• Damaged brickwork: Openings around foundations, wall joints and deteriorating building materials.

• Drainage systems: Defective drains and damaged pipe connections can sometimes provide access into buildings.

Rats are also capable climbers, so entry points are not always at ground level.

Can Rats Chew Through Walls to Make a Hole?

Rats have strong teeth that grow continuously, which is why gnawing is a normal part of their behaviour.

They can damage materials such as wood, plastic, plasterboard and some softer building materials. They may also enlarge existing gaps around pipes or damaged masonry.

However, rats cannot simply chew through sound concrete or solid brickwork as easily as they can softer materials. They are more likely to exploit an existing weakness.

Gnaw marks around an opening can be an important clue when investigating suspected rat activity.

How Can You Tell if a Hole Is Being Used by Rats?

The size of a hole alone is not enough to confirm a rat infestation. Look for other signs around the entrance and nearby areas.

Fresh soil, worn pathways through vegetation, droppings and gnaw marks may all indicate rodent activity. You might also notice greasy rub marks where rats repeatedly squeeze through the same narrow space.

If the hole is close to a building, check for evidence of activity inside as well. Scratching noises, damaged food packaging or droppings in cupboards and utility rooms may suggest rats have already gained access.

How Do You Stop Rats Getting Through Holes?

The most effective approach is to identify and address potential entry points before rats establish themselves inside.

Suitable rodent-resistant materials, such as properly fitted metal mesh or appropriate metal-based proofing, can help protect vulnerable openings. Damaged doors, vents and brickwork should also be repaired.

Avoid relying on expanding foam alone, as rats can gnaw through it. Never block essential ventilation, and do not seal an opening if rats may still be trapped inside the building.

Where activity is already established, the infestation should be investigated and controlled before permanent proofing work is completed.

Found a Rat Hole Around Your Property?

Finding a suspicious hole doesn’t automatically mean you have a rat infestation, but repeated activity around the same opening is worth investigating.

Youngs Pest Control provides professional rat control across Greater Manchester, Cheshire and Merseyside.

With over 35 years of experience, our family-run business can help identify rat activity, carry out appropriate treatments and advise on preventing further access.

For advice about suspected rat holes or entry points, call Youngs Pest Control on 0161 776 9832 or 07845 815 261.