How to Banish Mice and Rats From Your Home During and After a Renovation

There’s no better feeling than finally moving into your home after a major renovation. But that joy can quickly turn to dismay if rodents decide to move in along with you.

A general contractor must take measures during a renovation to keep out rats and mice. And exterminators recommend including a pest control clause in your contract that guarantees there will not be any mice or rats during a renovation, and for a certain time period following it.

Before a renovation, exterminator Ed DeFreitas, of Empire Pest Control, will consult with architects and contractors to come up with a rodent control plan. He charges $100 to $200 for a typical brownstone consultation.

In the kitchen, DeFreitas recommends sealing around all pipe openings behind base cabinets with a 3-inch-wide piece of quarter-inch wire mesh, and the walls with tight caulking where they meet the floors.

“Mice like to stay within about 10 or 15 feet of their food source,” DeFreitas said. “That means that once they have entered a structure and they have found the kitchen, they are probably going to stay close to that.”

Michael Corrao, of Cobble Hill Exterminators, said he is often called in after a renovation to seal up holes that contractors missed. He uses Xcluder, a type of steel wool, around all the pipes and baseboards.

“If you’re renovating, you want to definitely close up any gaps, any holes around the baseboards,” Corrao said. “I find myself doing a lot of jobs putting steel wool or caulk beneath the baseboards. I go through the radiators, and make sure all the piping areas are sealed, underneath sinks, behind the dishwasher and behind the refrigerator — those are the main areas.”

Before you install a run of new counters and cupboards, be sure the walls behind are solid — ideally reinforced with wire mesh where the wall meets the floor — and the ends of the built-in are sealed. Otherwise you could find yourself with a rodent highway and no way to block inaccessible holes.

To prevent mice and rats from entering a building, homeowners must tightly seal all openings on the outside of the building, such as holes for hoses, hatches and exterior vents. And during a renovation, workers must be sure to throw away food in a solid container like a metal garbage pail.

“The contractor must make sure that there is no food around,” DeFreitas said. “If they do have food around, the mice will move in, and it will become a serious problem.”

Rats usually travel along sewer lines and enter through holes in the cellar, such as openings around sewer lines that are not properly sealed. They can also squeeze in through openings in the foundation.

“If the person has got a house with a stone foundation, those walls have probably been around for over 100 years, and they’ve got multiple opening between the stones,” he said. “They need to be repointed to close any opening, at least on the front and back of the house, which is up against soil.”

Another common mistake contractors make is to leave sewer lines uncapped when removing a toilet or sink that is going to be replaced.

“Out of those drains will come rats or water bugs,” DeFreitas said. “Once they’re out, somebody has to get rid of them.”

If you are doing a full gut renovation, seal holes between neighboring houses — such as around joists and wood framing — when the walls are open to prevent mice from entering from next door. One Bed Stuy homeowner who did a partial renovation is still grappling with mice inside the walls of her wood-frame house.

“For us, having not done a full gut, we can never stop them running from house to house and inside the walls,” she said. “All we can do is plug up any holes with mesh and plaster so they can’t get into our living space. They are in the attic and there are parts of the attic that are unreachable.”

And the mice still return every few years.

“I find good repairs last about six years,” she said. “Then, they find new holes to chew through.”

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