Domestic rats on the rise since Covid-19

Residential rodent infestations increased 21% last year, says pest control experts Rentokil

Rodent infestations are on the rise. Enforced house arrest through two lockdowns and an increase in DIY activity in homes and gardens resulted in residential rodent infestations increasing by 21 per cent last year, according to one of the main operators in the pest control sector, Rentokil.

The counties with the biggest problems are the nation’s most urban. Dublin accounted for almost 28 per cent of Rentokil’s total rodent call-outs in 2020, while Cork came in second with almost 10 per cent of calls. These were closely followed by Galway and Kerry which accounted for 6 per cent each and Kildare with 5 per cent.

The reason is pretty straightforward. With restaurants, cafes and bars closed for long lockdown periods, rodents have had to adapt to a new normal too by checking out of the hospitality sector and into our homes.

Winter is typically the time when mice and rats head indoors, says Richard Faulkner, an advanced technological field consultant at Rentokil, but all that gardening we did during the summer has exacerbated the problem. “Briars, overgrowth and leaf litter all provided cover from their predators,” says Faulkner, who trained in environmental biology.


People have been home a lot more, so there’s more domestic waste about. “A house mouse does not hoard food. If you get rid of the food, you get rid of the problem.”

Swiss cheese

A brand-new, A-rated, airtight home should be vermin free, he says, but older housing stock can have more access holes than a Swiss cheese.

Old connections that haven’t been sealed properly offer entry points. A former outside toilet, for example, that has an extension built over it but where the builder left the sewer connection open. “If you have someone in to install cable, to fit the house with an alarm, to put in a new washing machine, that creates an access point.”

Terraced houses are particularly vulnerable. Rodents can roam from one to another via voids in the attic, behind skirting boards and in gaps between the ceilings of the ground floor and the floor above.

How do you know if your problem is mice or rats? The noise levels are no different, Faulkner says. “They both sound like elephants wearing hobnail boots. The size of the droppings is the giveaway.” Mice droppings are the size of rice grains while rat droppings are about three times this size.

“If you get rats in an urban area it’s more likely they’re coming through drains or sewers than through the front door,” Faulkner says.

Barry Benson, managing director of Dyno-Rod agrees. “The redbrick suburbs of Ranelagh, Donnybrook, Rathgar and Phibsboro are all prone to infestation. A lot of rodent call-outs don’t typically reflect the value of the house or its location.”

Beneath the joists

Builder Kevin Moran advises would-be renovators and period home-buyers to add a scrupulous check beneath the joists to their surveyor’s checklist. In one premium Dublin 6 home he renovated and extended, the owners called him back to address a rat problem beneath the suspended floorboards of their ground floor.

“They were overrun. The owner was catching one a day. He called me back to lift the floorboards and lay an insulated concrete slab at the base of the 5ft void beneath the timber floors. It seemed to eradicate the problem. A conservation architect may have a different approach though.”

James Nugent, a grade three conservation architect of Broadstone-based practice Studio 42, says this is an extreme approach. Instead he suggests sealing the exterior of the building and commissioning a CCTV drain survey to see where the origin of the problem lies.

Dyno-Rod is one of several suppliers of this service, which reveals subterranean breaks in the pipes. These will give rats a point of exit from the drains and from there they can burrow towards the house and gain access via any number of outside wall connections. It could be the plumbing of a washing machine where the pipe connection gap has been filled with foam – rats will easily gnaw through this – or a hole made for the installation of a outdoor tap or exterior lighting, says Benson.

Manholes are a big entry point, he says. “In the older areas of the city, like Stoneybatter in Dublin 7, where the chambers are made of brickwork, missing bricks will allow entry. Opening one will show scratching and evidence of activity.”

Rats are also at the root of about 40 per cent of the firm’s drain blockage call-outs. “After every unblock we put a CCTV camera down the drain to see if there are any problems. In these instances there is usually a hole, crack or break in the pipe. In some we’ve even caught the culprits on camera.”

Requests for rat-flaps – a cap applied to drains to prevent vermin accessing the homeowner’s private sewer from the public sewers – increased significantly during Covid. It costs about €185, ex installation.

So how do you deal with the problem? Rentokil call-outs start from about €160 but each situation is dealt with on a case-by-case basis, depending on the type of pest, the size of the infestation, the type of treatment required, the size of the property and the number of treatments. The company uses liveried vans, which will keep the neighbours up to speed, but in exceptional circumstances the firm says it can make alternative arrangements.

But if you want to avoid having the problem in the first place, Faulkner says the best deterrent is managing food waste effectively. “Keep bins away from the house and its doorways and keep doors shut. Don’t forget about pet food. Keep it in sealed containers like plastic bins.”

Benson’s last piece of advice is not to throw grease down the drains. “It’s an invitation to rats.”