Most homeowners, asked how a pest might get inside, would point to a door left ajar or an open window. But the gaps that actually let pests in as the weather cools are rarely the obvious ones. They are small, hidden, and often built right into the structure of the home, tucked behind appliances, low to the ground, or high on the roofline where no one thinks to look. Across Hamilton, Burlington, and Oakville, Action Pest finds these overlooked openings behind a great many fall infestations, and knowing where they hide is the difference between a sealed home and a pest problem you never saw coming.
The Gaps Built Right Into Your Walls
Some of the most-used entry points are not damage or wear at all, they are deliberate features of the building that were never meant to admit pests. Weep holes are the prime example. These small openings in the mortar joints of brick and stone veneer homes exist for a genuine and necessary purpose, allowing moisture trapped in the wall cavity to drain and the space to breathe. The problem is that a weep hole connects directly to the wall cavity, and at their typical size they are wide enough for insects, spiders, and even mice to slip through.
Brick and stone veneer is extremely common across the region, which means most homes have weep holes, and most of those weep holes go completely unprotected. The fix is not to seal them shut, since that traps moisture and causes rust and rot in the wall, but to install breathable weep-hole covers that block pests while preserving drainage and airflow. This is exactly the kind of nuanced, build-aware detail that separates effective exclusion from guesswork, and it is a recurring theme in the pest and rodent information Action Pest shares with homeowners.
The Vents and Utility Lines Nobody Inspects
The second category of overlooked gaps is the network of vents and utility penetrations that every home has and almost no one checks. Dryer vents are a frequent culprit. The flap on a dryer vent is meant to close when the dryer is off, but flaps wear out, stick open, or fail to seal, leaving a direct opening into the home that pests readily exploit, drawn by the warm, scented air. Bathroom and kitchen exhaust fans, attic and gable louvres, and HVAC intakes offer the same vulnerability when their screens are bent, rusted, or missing.
Utility penetrations are just as commonly missed. Every point where a pipe, cable, gas line, or wire enters the home is a potential gap, and these are frequently tucked behind appliances, under sinks, or hidden by landscaping, which is precisely why they go unsealed for years. The US Environmental Protection Agency recommends screening air intake and exhaust vents, covering fan and vent openings with galvanized mesh of a quarter inch or smaller, and sealing around plumbing penetrations including sill cocks and sewer lines. Because materials contract as temperatures drop, a utility gap that seemed snug in summer can open just enough by late fall to admit a determined pest.
The Garage and Door Gaps Hiding in Plain Sight
The third overlooked area is one people walk past every day: the garage and the doors themselves. An attached garage is a warm, sheltered transition zone that rodents use as a staging point before pressing into the living space, and the gaps that make it accessible are easy to miss. The bottom edge of a garage door rarely seals perfectly against the floor, and worn or damaged garage door seals leave a gap that runs the full width of the opening. The uninsulated door leading from the garage into the home, if it lacks a functional sweep or weatherstripping, then offers a second easy step inward.
Exterior doors elsewhere on the home have the same weakness. Weatherstripping compresses and cracks over a season of use, and door sweeps wear down and bend away from the threshold, leaving a gap at the base. The US EPA advises that doors which do not seal at the bottom should be fitted with weatherproof sweeps or have the threshold built up to ensure the gap is less than a quarter inch, since anything wider is enough for mice and many insects. A simple test tells the story: if you can see daylight around a door from inside, a pest can find that same opening.
Why These Gaps Matter More as It Cools
The reason these overlooked openings become so consequential in fall is timing. As temperatures drop, pests are actively driven to find warmth and shelter, so a gap that a pest might have passed by in summer becomes a sought-after entry point once the cold sets in. The seasonal contraction of building materials compounds the problem, subtly widening gaps around penetrations and along foundations exactly when pests are most motivated to use them.
The good news is that sealing these openings is straightforward once you know where they are, and it addresses pests of every kind at once rather than one species at a time. The US EPA’s guidance for residents reinforces that keeping pests from getting food, water, and shelter, and sealing the entryways they use, is the best way to prevent an infestation before it starts. General prevention advice is also available through Health Canada’s pest control tips. Because these gaps are so easy to overlook and require the right materials to seal properly, a professional inspection is often the most reliable way to find and close every one. Action Pest knows exactly where these hidden openings tend to be and can seal them before the cold drives pests to find them first.
Find the Gaps Before the Pests Do
The openings that let pests in as the temperature drops are rarely the ones you would guess, and that is precisely why they work so well for the pests that use them. Weep holes, worn vent flaps, garage transitions, and utility penetrations sit quietly overlooked until something slips through, and by then the problem is already inside. A thorough, knowledgeable inspection is the surest way to catch them all before the season turns them into open doors.
If you would rather close the hidden gaps than deal with what comes through them, Contact Action Pest today and seal your home before the cold sends pests searching.
