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Keep Mice Out

Summary: Catching mice is fairly easy. Learning how to keep mice out of your home is more involved. You need to know their habits, what environments they seek and what materials work best to rodent-proof your home.  You can learn more about rodent control products and/or purchase them here


Often I get questions asking what should be done to catch a mouse, but much less frequently do I get asked how to keep mice out. From a pest management professional's point of view, discovering how the mouse got inside in the first place would be my main mission. Sure, I'm interested in capturing the little rascal before he urinates and leaves his droppings all over my pantry items, but I know, again, from a professional point of view, that catching a mouse is a fairly simple task which can be done, in most cases, overnight.

I want to make sure that once I have eliminated the intruder, its relatives do not come calling. So, knowing the habits of the house mouse or field mouse is very important to gaining the upper hand in learning how to keep mice out.

The first thing is to closely examine the exterior of your home for entry points. Mice are great climbers, so you need to look high and low. Inspect any place

Sealing hose bib

where pipes or conduits come through a wall. Electrical lines, plumbing fixtures, air conditioning conduits, hose bibs and clothes dryer vents should all be totally sealed around their edges. It only takes a hole the size of a dime for a mouse to gain entry. That is only about one-half inch, but that is all it needs to squeeze its head through. The rest of its body can elongate itself and wiggle its way inside. I like a product called Xcluder for sealing up holes. It's inexpensive and very easy to use.

Most often we find mice get inside by getting under worn or missing garage door thresholds. New thresholds must be installed every few years to keep seals tight. Make sure the seals go all the way across the door to include edges. Same for pedestrian doors. If you can see light streaming under the door you can assume that the door will not stop a mouse. Hold a dime on its edge and see if you can hold it upright under the door threshold. Smart Park has a kit that includes everything you need to replace the garage threshold.

Mice love the cover of tall grass along foundation walls. You might think having nice, lush grass along the foundation wall looks good, but the negative aspect is that it gives mice the cover they seek. Eliminating vegetation along walls is one of the things we require of our commercial customers. Homeowners may be less willing to have a uniform bare strip running along their foundation walls, but, at the very least, keep this strip cut very low. Behind the cover of tall grass, mice can gnaw on lose or missing motor joints and discover an entryway into your house. Roundup herbicide does a nice job of knocking down unwanted vegetation along foundation walls.

Be sure to check joints where sidewalks meet the foundation of the house. Old or worn away joint filler can leave cavities that may provide access under slabs or expansion joints leading under slabs. If a mouse can get under a slab and burrow, it may eventually find where toilet plumbing comes up through

Garage door threshold

the slab into your home. Replacement joint fillers can be made of everything from rigid board impregnated with a blend of asphalts to cork fiber to rubber and more. I don't care what you use, as long as there is something filling that expansion joint.

As for the holes on the outside of the house I suggest using a quick setting concrete patch using a product like Quikrete. If the hole is meant to allow the passage of air you don't want to seal it, but you can fill it with the Xcluder stainless steel wool product I previously mentioned. Regular steel wool eventually rusts once wet and it is not recommended to fill these holes. You can also use hardware cloth to cover holes. Hardware cloth, which is not cloth at all, but rather a mesh of galvanized metal, comes in a roll and costs about $8.00 for a 3' x 4' sheet. You need a sheet metal cutter to cut it, but it is a very inexpensive way to seal up holes and rodents cannot chew through it.

Follow these suggestions and you will do a pretty good job of securing your castle from invading rodents.


01 Feb 2011, 20:47
I just realized that mice are living under a chair on my snow covered deck. The snow is high but I see them jumping through a hole in the snow bank. What can I do?
Ask the Exterminator
01 Feb 2011, 22:45
Remove the snow. Remove the chair. Duh!
18 Mar 2011, 14:03
We have what we think are field mice getting under our deck. The deck boards sit at ground height with the dirt covering any openings. Whatever is getting underneath is digging its way. The holes start out fairly small, that is why we think it is from field mice and not bunnies. We are in Wisconsin. They burrowed under and wintered there. There are many holes exposed now that the snow has melted from around the deck. We have filled in the holes in the past. They always redig. What can we do?
Ask the Exterminator
18 Mar 2011, 14:35
Filling in holes won't stop burrowing animals. Since the holes are under the house I would not suggest baiting the burrows. I would, however, suggest setting some small animal live traps to see what you can capture. Use a sunflower seed mix as bait. You can see this trap on this website at
08 Oct 2011, 09:15
Is there a way to tell if there's a gap between sections of the house near the foundation? We have a split level house and it seems like we hear mice between a wall where the 2 sections of the house meet.

And if so, how do you fix that?
Ask the Exterminator
09 Oct 2011, 08:34
If you cannot see it and are concerned, I suggest consulting a builder or structural engineer.
20 Oct 2011, 20:59
We have discovered rats living underneath our deck, which is built just above ground level creating effectively a crawl space. We are considering filling in the crawl space with a mix of large and small sized aggregate stones + sand to allow for drainage and fill up the spaces.

Does this have any chance of preventing the varmints from nesting under the deck?
Ask the Exterminator
21 Oct 2011, 11:42
The stone may help if it is properly applied. I would certain undertake a trapping program first to reduce the rat population.
Chris S.
18 Jan 2012, 22:20
I saw a mouse in my son's room and I swear it came out of the heating duct. Is there a product I can buy to keep this from happening? Any recommendations?
Ask the Exterminator
19 Jan 2012, 09:25
The mice have gained entry from the outside. You first need to seal up the places where the mice are entering the house. Then, you simply need to do some trapping to eliminate the mice already inside the house.
Sam W
18 Jun 2012, 17:37
I live in a city apartment and have a mouse problem in my kitchen. I left humane traps, snap traps, bait packs and bait stations. They have all been ignored and the droppings are now ending up on the counter and the top of the refrigerator. Any advice on what to do next? A friend told me that holding the traps with my hands puts my scent on the traps and the mouse will therefore not touch them. Is there truth to this?
Ask the Exterminator
19 Jun 2012, 12:01
Pre-baiting traps and proper placement is critical to catching rodents. Touching the traps has nothing to do with it. I've got lots of articles on how to pre-bait and place traps on my website. Just click on the "mice" category link in the list on the left side of any page.
Erin B
24 Oct 2012, 20:57
We have been dealing with mice coming in our storage area for over 2 year. We are catching them but the exterminator cannot see where they are coming in. This last weekend I found burrow holes with insulation in them burrowing under our front stoop. Our basement is fully finished other then the storage area where I usually catch them. How can I get to this area, what product do I use? I have small children so I have not used poison and I really don't want to smell they're rotting bodies. This completely makes sense...a few years ago I heard scratching in this same area. Please help:)
Ask the Exterminator
06 Nov 2012, 16:39
Try positioning snap traps near the openings of the holes. You might want to use the T-Rex mini traps. They will catch mice, but they won't break a finger of a child if the trap is tampered with.
Susan F.
13 Nov 2012, 13:59
I live in a NYC apartment. I had a recent infestation, had an exterminator come in, and blocked all the entry holes. The thing is now I hear them in my ceiling and my walls scratching and chewing away at night. I called my landlord and seems they can't do anything about that since they are not in my apartment. I am located on the top floor so there is no other apartment above me. PLEASE HELP, I am having nightmares that they will chew their way through the ceiling and walls to enter my bedroom. . . what can I do?
19 Nov 2012, 21:37
Thanks for this article, it's very informative. I only don't like the recommendation to use Roundup for vegetation control. I know it is (but don't think that it should be) sold everywhere, but that doesn't mean it is a safe product.

Roundup is a product made and marketed by GMO Monsanto to kill everything but its Roundup-ready seeds. Sounds good, but weeds have become resistant to it and used roundup (an endocrine disruptor) gets into the environment and finally us humans. I like to pluck out weeds, use darkening blankets/cardboard (which kills weeds), and/or use hot water to kill vegetation instead of enriching our resources with more toxins.
24 Nov 2012, 16:05
What can I do? The mice are burrowing from outside down past the footings and making swiss cheese out of the soil in my crawl space. The exterminator has just come back for the 3rd time this season to rebait the traps and he found several dead mice in the crawl space. They have stopped coming up into the house, but I hear them chewing on the bait in the crawl space. How do I stop them from burrowing into my house? I'm afraid they are compromising the footings for the house. Can I seal the basement with spray foam throughout or a thick plastic barrier sheet?
04 Feb 2013, 14:19
We have seen two mice coming up from the gas line in the floor of our family room next to our woodburning fireplace. I put some steel wool in the hole and think I have found the outside entry. The air conditioning conduit seems to have the foam all gnawed off. I put steel wool in that hole as well. If there is mice inside, will they die and/or where will they go? If they die will I smell them?
06 Feb 2013, 18:18
there is a small gap under my foundation were mice are coming up into the walls however they are stuck in the wall nowhere for them to get out. i am planning on sealing the gap but how do i get the mice out before i do so they don't die and stink in there. i know this is there entry based on footprints in the snow and tunnels
13 Feb 2013, 14:15
We have had a mouse problem in our house for several years. We are pretty sure they are getting into a crawl space underneath the house by first getting under our deck that is against that wall. We have put very small screen all around the deck, but to no avail. We think they may be coming up on the deck and getting between the boards and going under it that way. Do you have any suggestions? We've been told we can't seal all of the deck spaces because it will cause the deck to puddle and mold.
Ask the Exterminator
13 Feb 2013, 14:22
You can use Xcluder ito fill the problem cracks. Xcluder, which is sold on this website, is similar to steel wool, except the "steel" is stainless and won't corrode when exposed to weather. It will allow air and moisture to pass through, but not mice. You might want to discuss this with a deck expert first.
08 Apr 2013, 11:37
i cant get mice to stay out of the dressers in m house and they keep eating up my clothes what is the best way to get them outof the dresser and out of my house?
30 Jul 2013, 11:37
We installed new rubber stripping on our garage door (which is attached to our house) and mice keep chewing through the rubber seal. We put steel mesh at each corner and that stopped it for a while, but now they are chewing through the middle of the strip. is there anything we can do to prevent them from chewing through the rubber? Thanks.
28 Aug 2013, 12:13
We have mice entering our dryer vent and then that leads to our pantry. I just saw one scurry under our couch. I have read that steel wool can be used where the dryer vent tubing meets the exhaust hole in the wall. My concern is that steel wool is a Great fire starter. Won't it potentially catch our house on fire? That's one way to get rid of mice but I don't want to get rid of us! Thanks!
Ask the Exterminator
28 Aug 2013, 13:59
As long as you are not blocking the air flow of the exhaust pipe, using steel wool should be no problem. Personally, I prefer using Xcluder, as mentioned in the article above. Xcluder is made of stainless steel wool so it won't degrade over time.
30 Aug 2013, 17:40
Ok, so here's the situation. I recently moved in with my Father after he went ill (terminally, maybe 6-8 months), to take care of him. My Mother has already passed and after his diagnosis he sold his house to pay for medical bills, etc. In our house growing up, I never seen one bug... literally. He now rents a mobile home (it's newer), mainly due to it's what I can afford (I'm a Teacher). After I moved in, I started to notice weird things, little droppings in cabinents, my towels under the sink started to get holes, the smell under sinks were old smelling, my computer wires had chew marks, etc... anyhow, I had my ah-ha moment and understood that we had mice. Then, one night I went into the kitchen and turned on a light and a mouse ran right by me. I was so freaked out and literally stood on a chair for 3 hours crying hysterically. Shortly after, I tried to tackle the problem after reading as much as I could on the web. I pulled everything out of kitchen, cleaned with bleach, sealed every single opening I could find in under counters, behind stove, fridge, dryer, washer, baths, etc, I packed every non essential in plastic tubs and put down traps (any kind I could get my hands on). I've caught 3 in a week. I then had a friend come and look under the mobile home and see if he could see any access points, etc. He said that there were "many" that could potentially be ways for the mice (FIELD MICE) to be getting in and it also appeared that some holes had been half-assed patched before we moved in. I asked the landlord to fix any holes on the outside or under the mobile home however was told that it was not the landlords responsibility. I know this is a long narrative... but as a young female (who obviously is terrified) I don't know where to start on the outside/under the house. The landlord suggested I leave the holes open and put a "block" of lethal bait and let them die off. Then another friend offered advice to seal any points outside first so that they don't die in walls and/HVAC (where I believe they are). I contacted some exterminator companies and was told that they only put out bait and do not seal access points under or around outside of house. Do I then hire a contractor? Do you have any idea how much it would cost to have someone seal possible entry points? I figure I could do whats visable around the mobile home with durable products. I am in no way going under the house. Is there anything else I can do? Thank you for listening and/or giving any advice!
04 Sep 2013, 15:58
hot to keep mice out of the air conditioner unit outside?
06 Sep 2013, 09:46
My daughter lives in a first-floor apartment and she has problems with mice. The apartment has heat/ac vents on the floor and we think that's where the mice gain access to her apartment. Other tenants have problems with mice as well. Since it's an apartment building and not a place she owns, there is but so much she can do herself as far as sealing pipes, etc., to keep the mice out. Is it safe to use the galvanized wire cloth to secure over the floor vents, and what other options does she have? She's using traps for any mice that may come in but she wants options to keep them out in the first place. Any advice you can give will be greatly appreciated. Thank you.
Ask the Exterminator
06 Sep 2013, 11:33
Galvanized wire cloth will certainly prevent mice from entering. However, it does not stop the problem, as you well know. The landlord is obligated to provide a pest free environment. It's the law.
08 Oct 2013, 19:38
I hear a mouse something in my a.c vent. I live in mobile home so vents are on floor.Hoe can i trap it before i causes damage?
Ask the Exterminator
10 Oct 2013, 10:57
Try putting traps inside the floor vents. If you can find mouse droppings or evidence of something the mouse is eating, place the traps near those locations. Use lots of traps. Most homeowners put out one or two traps, but if you put out a dozen traps you will speed the process.
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