How To Find Where Mice Are Coming Into Your House

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Are any invaders more unwelcome than mice? If mice have infested your home, removing the ones inside will only solve part of the problem. You’ll also need to identify how they entered, so you can prevent other mice from taking up residence.

Mice carry diseases, destroy property, and otherwise create problems for you and your family. Fortunately, there are a few simple steps you can take to keep them out of your home for good.

How Do Mice Get into Homes?

Mice can enter homes through any external opening the size of a pencil width or larger. The most common entry points are gaps and cracks in the foundation, roof, and walls. You’ll need to look in hidden areas such as under porches and behind foliage.  

Mice also follow pipes, wires, and other conduits that cross between the interior and exterior. Small spaces within the framework can expand due to water damage, age, and chewing, which allow mice to squeeze between the structure and the pipe or other object.  

Another popular entry point is through torn screens or underneath door sweeps. Mice can scale buildings and enter through damaged screens on any floor. If a screen has an opening larger than a dime, a mouse can fit through it and will do so to keep out of the cold.  

How to Find Where Mice are Getting into Your Home

Identifying where mice are entering your home is a two-step process. First, you’ll need to find all potential entry points, such as cracks and gaps in the exterior of your house. Once you’ve located these, you’ll want to look for signs of mouse activity.

Mice leave behind a black, oily, waxy substance called sebum. They produce this secretion as they press against walls and objects. Sebum acts as a guide for other mice, signaling the presence of desirable conditions. Sebum trails draw mice, who then create more sebum and attract more mice, resulting in an ever-growing infestation.

Another sure sign of mice is droppings around your home’s exterior. Mouse droppings are dark, rice-shaped, and about one-quarter inch long. These mouse pellets help identify potential entryways, as mice leave behind 50 to 75 each day.   

What You’ll Need

Before searching for mouse entry points, you’ll need to gather up the following equipment:

  • Goggles
  • Face mask
  • Gloves
  • Light source (headlight or flashlight)

Mice pose many severe threats to human health, primarily by carrying diseases like salmonellosis, hantaviruses, and plague. You’ll want to protect your eyes, skin, and lungs from exposure to any bacteria or toxins, especially in confined spaces like attics.  

Watch & Follow the Mice

Mice behave predictably when encountering a threat, such as a person. They’ll flee towards the closest entry point because they’re familiar with the territory. If you spot a mouse, watch where it runs, as it’s likely heading towards an opening in the exterior of your house.

Of course, mice move fast, so you’re unlikely to see them directly enter a crack or gap in the wall. However, they can point you towards a general area of your house which you can search more thoroughly. 

Inspect Your Attic, Basement, & Crawl Space

The three areas in the average home most popular with mice are the attic, basement, and crawl space. They often find nesting materials, food, and water in these locations, making them attractive places to stay.

You’ll want to examine those areas for cracks and gaps carefully. One effective technique is to have a partner shine a light along the walls from inside while you stand outside and look for flashes of light.  

Watch Over Areas with Food

The kitchen is another area of the house mice often seek out. To deter mice, you’ll need to put all food in either glass or metal containers, as mice will chew through plastic and paper.

Always keep your kitchen clean. Even small morsels of food attract mice, so wipe up any crumbs and spills immediately. Don’t leave dirty dishes in your sink or your dishwasher for extended periods.   

Check your kitchen from top to bottom for signs of mice. Look inside cabinets, underneath the sink, and in other out-of-the-way locations. Sebum trails, shredded paper, and droppings are all signs of an infestation.  

Inspect Holes from Wiring & Plumbing

Pipes and wires often provide easy access points for mice to enter a building. Even though the spaces around wires, pipes, and other infrastructure are small, mice can still squeeze through them.

Blocking the spaces around wires and plumbing can be done in several ways, such as packing the hole with steel wool or patching the area with metal plates.

What Damage Can Mice Cause When They Get Inside Homes?

Although small in stature, mice can cause substantial damage to people and property. In their quest for food and nesting, they’ll chew through furniture, walls, containers, and much more. Aside from the damage, they also make lots of disrupting noise as they scurry through walls and across floors.

Additionally, mice pose significant health risks. As discussed above, they can carry many serious diseases such as rat-bite fever, plague, and leptospirosis. Mice also carry fleas, ticks, mites, and other smaller pests, many of which contain diseases of their own.

How to Keep Mice Out Of Your Home

You should employ several strategies to keep mice out of your house. For the mice already in your home, you’ll want to set traps or enlist the services of a professional exterminator to get rid of your unwanted guests.

You also need to make the environment in and around your house less enticing to mice. Not only do you need to keep the inside of your kitchen tidy, but you should also clear the outside environment. Remove firewood, leaf piles, tree branches, and similar growth from near the sides or roof of your house so that mice don’t have places to hide near your home.

Mice rely on their sense of smell for navigation, and you can disrupt this by placing scents around your home. Some scents that can repel mice include peppermint oil, vinegar, ammonia, and mothballs.


Mice infestations can result in health risks to your family and damage to your home. While removing the mice inside is particularly important, you also need to prevent more mice from entering your home by identifying and blocking all potential entry points.

Fortunately, by understanding mouse behavior and enlisting the help of a professional exterminator if needed, you can get rid of any mice you have and prevent others from returning.

Jake Garza
Jake Garza
Jake is the founder of Hama Pest Control, the preferred choice for pest removal and extermination in the Greater Toronto Area. With over thirty years of experience, Jake prides himself in bringing quality, knowledge, and care to Hama Pest Control's customers.
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