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How Do Rats Get In Your Home?
Rats are resourceful, determined, and far more physically capable than most people realise. A Brown Rat - the species most commonly found in Irish homes and sewers, can squeeze through a gap no larger than a €2 coin, gnaw through wood, plastic and mild steel, and swim through the drainage system to emerge inside your property. Their constant search for food, water, and shelter during the colder Irish months drives them toward any home that offers these comforts.
Understanding how rats gain entry is the first step to keeping them out. Below you will find the key entry points used by rats in Irish properties, practical proofing steps to seal them, and advice on what to do if you suspect an infestation has already begun.
How Rats Get Into Your Home: Key Entry Points
Rats do not need a large gap to gain entry. They will exploit existing weaknesses and, if necessary, create new ones by gnawing. The following are the most common entry points in Irish residential properties.
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1. The Roof and Eaves - Rats are accomplished climbers. Black Rats (Rattus rattus) can scale any slightly roughed surface and are particularly associated with elevated entry via roof spaces. Brown Rats, while preferring ground level, are also adept climbers and will use drainage pipes, utility cables, and rough brickwork to reach upper floors and roof spaces.
Cracked or missing roof tiles, open gaps under the eaves, and loose soffits all provide access to the loft, a warm, quiet, undisturbed space that is ideal for nesting. Once in the roof space, rats can move downward through wall voids to the rest of the property. -
2. Air Vents and Air Bricks - Air vents and air bricks often have openings wide enough for a rat to squeeze through, particularly if they are damaged, corroded, or simply un-meshed. These fittings are found throughout Irish homes, typically at ground level and in cavity walls, and are a frequently overlooked entry point.
Rentokil Ireland recommends covering all air bricks, vents, and utility openings with sturdy, galvanised wire mesh with a gap size of 5mm or less to block entry while maintaining the ventilation function. Our award winning Flexi Armour Range has been developed specifically for this purpose and our weep vent proofing is specifically designed to stop rats gaining access to cavity walls via air vents and bricks. -
3. Gaps Around Pipes and Utility Entry Points - Wherever a pipe, cable, or utility line enters your property, gas supply, water pipes, telecommunications cables, electrical conduit, there is a potential entry point. These gaps are often present in new builds as well as older properties: contractors routinely leave small spaces around pipe entries, and over time mortar and sealant around utility penetrations can crack and crumble.
Rats possess the strength to gnaw through plastic, wood, and soft metals, meaning they can enlarge an existing small gap into a usable entry point. Structural defects such as hairline cracks in mortar or weep vents in brickwork can similarly be widened by persistent gnawing. Our Flexi armour range of building seal mesh can be quickly installed around the outside of cladded buildings as a complete blockage to rats and rodents. -
4. Doors and Worn Door Seals - Gaps beneath doors, particularly in older Irish properties where timber doors have warped or where brush strips have worn, are a common ground-level entry point. A gap of only a few millimetres is sufficient for a rat, given that Brown Rats can compress their body to fit through an opening the size of a €2 coin.
Rentokil Ireland offers the Flexi Armour Door Proofing range, exclusive to Rentokil, which provides flexible but robust seals for both standard pedestrian doors and roller loading doors. This eliminates the gap at the base of the door without restricting use. -
5. Drains, Sewers and Soil Stacks - The Brown Rat is the only rat species that lives in sewers. Excellent swimmers, Brown Rats can hold their breath for extended periods and travel considerable distances through the drainage system.
Where no non-return valve (rat valve) is fitted to the drainage pipework, they can swim through the U-bend and emerge through the toilet bowl, a possibility in many older Irish properties with ageing drainage infrastructure. Beyond toilets, rats exploit fractured sewer pipes, uncapped drain joints, and gaps where utility plumbing exits walls, for example, behind outdoor taps or beneath kitchen appliances. They also climb vertically inside soil stacks to access properties through broken joints or open roof vents. -
6. Basement and Foundation Gaps - Brown Rats prefer to burrow near solid structures. Rat burrows are typically 6–10cm in diameter and are found along building foundations, under garden sheds, and in dense vegetation. Where burrows connect with gaps or cracks in basement walls or floor slabs, rats gain direct access to the interior.
Flooding and heavy rain, which are common occurrences in the Irish climate, can displace Brown Rats from their ground burrows, forcing them to seek alternative entry points above ground level. After any storm event, inspecting foundations and lower walls for new gaps or signs of burrowing is a recommended precaution. -
7. Overgrown Vegetation and Garden Access - Climbing plants, dense shrubbery against exterior walls, and overhanging tree branches provide rats with the cover and access routes they need to reach upper parts of your property. Overgrown vegetation close to building foundations also provides shelter and potential nesting sites that keep rats in close proximity to your home.
Trimming back tree branches from the house, cutting climbing plants away from walls, and keeping grass short to reduce ground-level cover are all practical rat deterrents recommended by Rentokil Ireland.
How to Stop Rats Getting Into Your Home: Proofing Guide
Proofing your property, physically denying rats access to entry points is the most sustainable and cost-effective form of rat control. Once rats establish a nest and begin breeding, a single pair can produce over 1,000 offspring in a year, making prevention significantly easier and cheaper than treatment.
Worried About Rats?
If you think you have rats, it is important to act quickly to control the level of infestation and reduce the health risks posed by this rodent.
You can also take practical steps now to proof your home or business and prevent rats. Rentokil Pest Control can provide you with a professional service and bring peace of mind if you feel you have a rat infestation.
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Frequently Asked Questions
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Why would rats come into my house?
Rats are driven by three core needs: food, water, and shelter. Brown Rats, Ireland’s most common species, need up to 30g of food and between 15ml and 60ml of water daily, and cannot survive without a consistent water source. During colder months, or when flooding drives them from their burrows, any property that offers warmth, food scraps, or accessible water becomes a target. The smell of domestic waste, unsecured pet food, bird seed, or a garden compost bin is often sufficient to draw
rats toward a property. -
Will a rat go near a sleeping human?
Rats are "neophobic," meaning they are naturally wary of humans and large movements. They do not seek out human contact; however, they are opportunistic foragers. If there is a food source in a bedroom or if an infestation is severe, they may venture near a sleeping person while exploring. Bites are extremely rare and usually only occur if the rat feels trapped or accidentally provoked.
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Is it possible to only have one rat in the house?
Technically possible, but highly unlikely. Rats are social animals that live and move in colonies. If you have seen one rat, there are almost certainly others nearby — in wall voids, beneath floorboards, or in the sewer system connected to your property. Because a single pair of rats can produce over 1,000 offspring in a year, a small and apparently contained problem can become a severe infestation in a matter of weeks without professional intervention.
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How long will a rat stay in your house?
A rat will stay in your house as long as it feels safe and has access to food. Once they have established a nest and marked "safe trails" with their pheromones, they have no reason to leave. Without professional treatment or the complete removal of their food and water sources, a colony will remain and grow. Brown Rats are also highly resistant to DIY control: they are intelligent, quickly become bait-shy if they encounter an ineffective product, and breed faster than traps alone can reduce the population.
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Can rats come up through the toilet in Ireland?
Yes, it is possible. Rats are incredible swimmers and can hold their breath for several minutes. In many Irish towns and cities with older drainage systems, rats live in the sewers. If there is no "non-return valve" (rat valve) installed in your pipes, they can swim through the U-bend and emerge in the toilet bowl. This is rare, but it is a genuine reason why many Irish homeowners opt for professional drain proofing.
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Can rats get into a new build in Ireland?
Yes. Even modern Irish homes have vulnerabilities. Rats frequently exploit gaps left by contractors around utility pipes, cable entries, and poorly fitted weep holes in brickwork. If ground was disturbed during construction, it can also displace existing rat colonies, sending them in search of new shelter, and your new build may be the closest available option. The Rentokil Ireland blog also notes that modern, heavily insulated structures can develop internal condensation pathways that retain moisture, creating conditions rats find attractive.
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Why are rats in my attic but not my kitchen?
Rats prefer to nest in quiet, undisturbed areas. Your attic (loft) is the warmest part of the house and provides excellent nesting material like insulation. They use the "wall cavity",the gap between your internal and external walls, as a private ladder to move between the drains and the roof. They may be feeding outside or in other parts of the house at night while you are asleep, leaving the kitchen seemingly untouched during the day.