The joys of living in a 30 year old home constructed by a builder that slapped up hundreds (maybe thousands, several neighborhoods near us look similar) of homes in the eighties and early nineties, in what used to be woods...
The previous owners told us about the flying squirrel they had the previous year in the attic, which was removed and hole repaired (poop not removed... that's apparently my "duty"), but they seem to have covered up a rather significant field mouse problem in the basement. Last summer we started noticing chunks of nuts and mouse poop in the basement. Come to find that the plywood that "sealed" (using that term loosely, see builder comment above) the base of the kitchen bay window was thoroughly rotted, and the plywood sealing the base of the dining room bay window didn't cover the entire opening. Naturally, mice, gophers, squirrels, mountain lions, man-bear-pigs, small dogs, and so forth had full access to the basement. At this point, we've pulled out and replacement half the insulation in the basement after finding nuts and poop everywhere, replaced the rotted wood on the one window, and added plywood to the other to close it up. I did the best I could to seal both up with expanding foam outside, but that was next to impossible with the ground less than a foot away.
This month, field mice taught us two things. 1 - The replacement plywood wasn't fully screwed up like I thought it was and 2 - the garage door weatherseal used 30 years ago was doing literally nothing. We were still finding fresh poop in the basement, the new insulation I installed was loaded up with poop and nuts, and we found poop in the back corner of the garage that is up against the basement.
We set traps in the garage and caught one right in front of my car, so I ripped the useless metal trim from the around the vehicle door and nailed up new plastic trim with rubber seals pressed up tight to the door. I also pulled off the old bottom bulb seal and installed a new one after finding a company that restarted manufacturing of the old type seal for Stanley garage doors. No more mice getting caught in the garage... and the temp inside remained over 40F even when it was in the teens overnight. Double win.
Downstairs, I used rodent-type expanding foam inside the bay window that wasn't screwed tight and filled in all the edges. I'm not feeling anymore air gaps now. I did this after traps down there caught two mice. Leaving the insulation out another week to make use of all the below freezing nights we have left and see if any more of them come in. If not, I'll reinsulate, then tear out ALL of the remaining original insulation and the faced insulation they had slapped up to cover the problem from our inspector, and replace it all with fresh attic/crawlspace rated unfaced R30.
We must be making headway. Last summer, our neighbors said they had no issues. One of them did when she bought her house 7 or 8 years ago and she had it taken care of, and loaned us her traps. Last week our other neighbor who is have a $50k kitchen and bath reno done said she found nuts on some of her totes in the basement... they must be looking for other places to go as a result of finding our house harder to get into.
Doesn't make sense that they keep coming to us, we don't keep food in the basement, garage, or outside. Usually try not to put trash in the cans outside even until just before trash day (today).
Hoping that's the end of it... and the freshly sealed door helps even more. I still need to put some wood putty on the surrounding door trim where the previous owners let leaves collect and rot the wood and old metal trim.
2002 Chrysler 300M Special - Deep Sapphire Blue/Storm Gray Metallic - 142,000 miles