Whether you think mice are adorable or you shriek and faint at the sight of them, one thing is certain—you don’t want them in your house. Of course, the ultimate goal is to keep the mice away, but before you try to keep them out, we must first consider the routes they take to breach the walls and slip inside.
But how exactly are the mice getting into your home? You would be surprised at the many crafty ways that mice have to penetrate the four walls of our cozy homes.
Mice are very resourceful creatures. They will seek out the easiest point of entry to find a nice secure place to raise their families. And not only do they find these entry points with their sense of sight and touch, but they can also feel the smallest warm draft with their keen senses to help identify a potential weakness in your fortress.
How Do The Mice Get In?
Rats and mice typically use these entry points:
- Sills and ledges on windows and doors
- Fence railings
- Weak foundations and materials
- Gaps between materials
- Electrical wires
- Weep vents and water conduits
- Door and window frames which are poorly sealed
- Roof vents, air conditioning, and heating units
- Tree branches
Keep in mind that mice can climb walls very effectively, so they don’t necessarily need a tree branch to find their way onto a second-story window ledge. Also be aware that they can fit through incredibly small openings. All a rat needs is an opening of about half an inch. A mouse can make it through an opening half that size—approximately the diameter of your little finger!
To find the likely points of penetration, first, check around the perimeter of your house and look for weaknesses. Decaying building materials, branches, and pipes that could be acting as pathways, and even tiny holes are all potential routes into your home. It may take you a few rounds and a few hours of serious methodical hunting to find these points of entry.
In fact, many homeowners miss these holes for years even while searching everywhere for them. In some cases hiring a professional exterminator or handyman can speed up the process of elimination to find the gaps. It really only takes one point of weakness to cause a mouse problem. Now that we know how the mouse got in, its time to focus on how to keep mice out of your house!
Keep the Mice Away from the Outside of Your Home
Habitat reduction is actually the easiest way to prevent the mice from coming inside. If there are no mice living nearby, you have drastically reduced the chances of having a mouse problem in the first place.
Start by making the area around your house a less hospitable place for rodents. Cut loose brush and keep grass neatly trimmed. Get rid of any debris and garbage you have lying around, and remove food and water sources that rodents may find convenient in your yard.
This includes common yard items like bird feeders, empty pots or wheel barrels that may collect water and hiding areas like a compost or wood pile.
Consider installing a barrier of cement or rock around your home. This is about making mice feel less safe. Mice hate to cross open areas where they might be spotted by a predator. For more information on mouse-proofing the garden, see our article on ten ways to keep the mice out of your yard.
Of course, you may not be willing to give up the lush garden or landscaping that took years to cultivate. In that case, you’ll need to securely mouse proof your house, both inside and out.
How to Mouse Proof Your House
Once you patrol your perimeter and identify the potential weaknesses that the mice could exploit, it is time to learn how to mouse-proof your house. For that, you are going to need to buy the proper materials.
Rodent Proofing Materials
Invest in rodent and mouse-proofing materials for your house. These include:
Steel wool hardware cloth (look for 19 gauge and heavier). Steel wool is a common way to mouse-proof small crevices and gaps around the house. If you find that steel wool is rusting too quickly, you can try replacing it with copper wool. Copper wool is sold in rolls that can be cut with scissors which makes it easier to wrap around pipes and cut it to the size needed. Install this in the holes that mice are using. It should hold up better over time.
- Perforated or sheet metal. Used to seal foundation gaps and holes.
- Cement mortar. This will be used to permanently seal any gaps around pipes and foundations.
- Sealing foams and caulks. These are best when applied inside the home around areas where cement is not appropriate like windows or doors. Keep in mind, they typically work for a while, and then mice and rats just chew their way right through them. So they are a stopgap measure at best and may need to be replaced every so often.
- Pest Control Door Sweeps. If there are gaps of 1/4 inch or more under your doors, you may want to install a rubber door sweep to seal the doors more securely. These can also act as a weather barrier that can save you money on heating & cooling the home.
You are going to use these materials all over your home to seal up holes and vents as necessary.
Sealing Your Structural Gaps
Once you have the materials you need, you are ready to seal the structural gaps in your home.
Pipes and fixtures: Holes around your pipes can be patched up using concrete or mortar. Keep in mind that mice are quite persistent. If you try to fill a hole with cement, mice will sometimes attempt to burrow through while it is drying and create new weaknesses. Prevent this by adding shards of glass to the mix. This will dissuade them from attempting to undermine your new solution.
AC/heating units: You obviously do not want to seal your air conditioner or heater off completely, or you won’t have any airflow. Use mesh to seal off access as best you can. If you use a sound blanket, consider dispensing with it, as mice tend to view these as a form of shelter, which makes your AC unit look inviting. So ditch the blanket and put up with the noise if you can. You may find you get used to it. At least noise won’t chew through wires in your house and breed up a storm of disease.
Eaves and Foundation Gaps: Eaves and spaces between materials like brick or foundation: There are a lot of options for filling these holes. You can use cement, caulk, or plaster, or you can cover them with steel wool or sheet metal. Unintentional holes and design flaws can typically be filled in completely. Other gaps which are intended to exist should be covered with steel wool or mesh so that your house can breathe. You don’t want to cut off airflow, only mouse access.
Weep holes in Brick: Weep holes are small gaps found in brick or cement foundations that need to stay open to the passage of air and water since they serve a functional purpose. For this reason, you need to purchase a flexible, coarse fabric mesh which you can use as a permanent barrier. This mesh will allow water and air to get through, but it will keep out the unwanted guests. You’ll need to check the mesh plugs over time since depending how it was installed, it can get clogged with debris & prevent proper air flow.
Another simple, but elegant solution is to use a weep hole insert. A weep hole insert is a pre-made stainless steel barrier that was designed specifically to fit inside the weep hole preventing mice and other pests such as snakes, wasps or lizards from entering the home. We tested this product recently and we’ve found it to be a much better solution than using cheap mesh to plug the gaps found in brick homes.
Window Doors and Frames: If the frames of your doors and windows are poorly sealed, buy some sealant and start filling the gaps. This will not only keep mice out of your home but will also keep your windows and doors from leaking. Keep a regular eye on these sealed spots. Mice may still try to chew through your sealant.
Securing Your Fortress Against the Rodents
It will take some time and an investment of money before you can thoroughly mouse-proof your house. To some degree, this is a process of trial and error. While many measures are simple and should help right away (like clearing away brush and garbage), others may require testing. You may find that one type of mesh isn’t doing the trick and you may have to try another, for example.
If you stick with it and you keep cracking away at the problem, you will gradually cut off access and make your house and yard less and less appealing to mice. When it becomes easier for them to simply go and pester your neighbors, your problem should be solved!