In order to defeat the rodent, you must become the rodent. 

During our home inspection, I recalled seeing a collection of acorns in various corners of the basement. I informed the homeowner and negotiated remediation as part of the sale. We assumed the problem was solved by professionals and we happily moved into our home. It was only a few short months later that the telltale signs of mouse activity started to resurface. Honestly, the issue was probably never solved and I just didn’t monitor the issue closely enough. But after awhile, the issue got severe enough that it was impossible to ignore. Baby rodent randomly laying in the middle of our basement? Yup, we had that. But if you don’t find squeaking newborn mouse babies in your basement, here are a few of the other more common signs that you have a rodent problem: 

  • Mouse droppings – they look like little black sesame seeds
  • Nighttime noises – this picked up more recently as warm summer nights transitioned into cool and below freezing fall nights
  • Gnawing and loose debris – this includes bite marks and other shredded items
  • Damaged food products – my COVID-19 stockpile had been raided
  • Outdoor food remnants  – I have multiple oak trees on my property and found countless acorns strewn across my basement
  • Evidence of a nest – remember the mouse baby I found? Eventually I found the entire nest in a shelving unit left by the previous homeowner

Things to Consider When Looking for Mouse Entry Points

I’ve talked to plenty of exterminators and even they said there is no real way to fully get rid of mice in your home. But frankly, that didn’t seem like a valid excuse for me not to try. I started by doing a bunch of fundamental research on mouse activity. In order to defeat the rodent, you must become the rodent. The key pieces of information I found most interesting and useful to my particular situation were: 

  1. Mice can squeeze into holes only ¼ of an inch big (source). WHAT? Yes, that fact literally blew my mind. I was anticipating finding a giant gaping hole in my siding where the mice were entering. At the very least an obvious sign of entry. But trying to find a ¼ inch hole around my house felt like trying to find a needle in a haystack.
  2. Once mice find a route into your home, they won’t stop. One of the things to look for when hunting for your entry point is a dark grey, greasy/waxy looking stain. This is called sebum which is an oil that’s secreted by mammals. It’s odorous and helps mark the trail for rodents to enter your home (source). 
  3. Consider your options when sealing any holes you find. This will obviously depend on your particular point of entry. Some of the options I researched included spray foam, caulk, copper wire mesh, steel wool, and peppermint oil. According to an informative video I watched, caulk, mesh wire and steel wool seem to be the most effective solutions for keeping mice out. Spray foam and peppermint oil are not as effective on their own. (source).  

Armed with these three pieces of information, I embarked on a journey to seal out mice from my home once and for all.

Tackling Our Mouse Problem

Based on the activity in my basement, I had suspected there were two primary locations critters could be entering. As such, I started my investigation in these places. Almost immediately I identified an area of entry by the walkout cellar doors. At the base of the stairs, a small portion of the door moulding had been chewed away at the bottom, revealing a rather large entry point directly into the basement. I thought “huzzah, I’ve found my issue.” I quickly vacuumed out the area and filled the hole with copper mesh wire. Assuming I had solved the issue completely, I congratulated myself on a job well done and took the rest of the day off.

Over the course of the next week, the amount of mouse activity in my basement really started to pick up. Since it was starting to get cold outside, nighttime activity was at an all time high as the mice sought reprieve from the blustery outdoor conditions. I quickly realized I had not yet solved my issue. The following week I kicked things into overdrive. I got down on my hands and knees and crawled around the foundation of my home, gently running my hand under the bottom siding to identify any obvious (or not so obvious) points of entry. I filled any hole, no matter how small, with bits of copper mesh. 

After circling my entire home, I hadn’t found any obvious points of entry. I felt defeated but was determined not to give up. As I circled towards the front of the house, I honed in one the last potential point of entry: the front stoop. This area was right above where the majority of the mouse activity in my basement seemed to happen. After a quick inspection of the brick stoop, I noticed a very thin and long gap between the top of the stoop and base of the door frame. During our home inspection we were informed the front stoop had settled and would eventually need to be replaced. The settling resulted in a rather large gap which I hypothesized (and hoped) could be the primary entry point of the mice.

mouse-entry-point-under-front-door

After a quick trip to Home Depot, I returned with a few tools to resolve the issue. Keep in mind, this is only going to be a temporary fix and will need to be continually monitored until the stoop is fully replaced. Unfortunately that’s not in the budget right now, so this roughly $24 fix will do for now. What I needed for the job: 

  • 1 Pack of Stuff-fit Copper Mesh – $18.99 on Amazon (link)
  • 1 Tube of 10.5 oz. Gray Drylok Masonry Crack Filler Cartridge (2-Pack) – $9.36 /package. I only used 1 tube at a cost of $4.68 (link)
  • Backer Rod – varying widths since the width of the gap changed – about $4.00, but I probably only used $1-$2 worth for the project (link)

mouse-entry-point-under-front-door-with-copper-mesh-wire

Steps to Seal the Crack

  1. Clear any debris away from the crack. I used my leaf blower to ensure all of the dirt, debris, acorns, leaves, etc. were removed. 
  2. I cut sheets of copper mesh, balled them up, and stuffed them into the cavity as far back as possible. I continued to do this until the copper mesh was filling the entire cavity. I also went around the entire stoop and filled in any additional holes with copper mesh that I found. 
  3. I then inserted backer rod into the cavity giving me about ¼ of an inch to apply caulk
  4. Apply the caulk to completely seal the gap

mouse-entry-point-now-sealed

After I completed the job, I headed to the basement and set a number of snap traps in my usual areas of high activity. Low and behold, the next morning the traps were empty and the bait untouched. I’m happy to report that my basement has been mouse free for the last two weeks since the job was completed. 

In the future I’ll be sure to implement the following steps to help reduce the likelihood of mice entering my home: 

  • Keep any food stored in the basement in secure mouse-proof containers
  • Keep boxes organized and sealed
  • Keep the area generally tidy
  • Avoid storage units with enclosed bottoms or other areas mice could take up residence
  • Continually monitor past entry points for signs of attempted entry

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