Every pest problem inside a house started with an entry point outside it. That’s the part of pest control that gets skipped most often. Treating what’s already inside matters, but if the way in is never addressed, the same problem tends to return with the next season.
Where Pests Actually Get In
The list is shorter than most homeowners expect, but each spot needs a specific fix.
- Gaps under exterior doors. A gap you can slide a pencil under is wide enough for mice, and even a smaller gap lets in ants and spiders.
- Utility penetrations. Cable lines, gas lines, and dryer vents all pass through the exterior wall, and the seal around them degrades over time.
- Foundation cracks. Settling homes develop hairline cracks that widen slowly, and pests exploit them long before they’re visible from a distance.
- Roofline and soffit gaps. Squirrels, bats, and wasps all look upward for entry points that homeowners rarely inspect.
- Garage door seals. These wear out faster than most people realize and are a common overlooked entry point for rodents.
- Weep holes and vents. Brick veneer weep holes and foundation vents are built-in gaps by design, and without proper screening they double as an open door for insects and small rodents.
- Chimney caps and flues. An uncapped chimney flue is one of the more overlooked entry points for raccoons, squirrels, and birds looking for a den site, and a missing or rusted-through cap is easy to miss from ground level.
- Dryer and bathroom exhaust vents without flaps. A vent hood missing its flap, or one that’s rusted stuck open, gives mice and insects a straight shot into the wall cavity behind it.
Why Sealing Works Better Than Repeated Treatment
Treating pests that are already inside deals with the population you can see, but it doesn’t change the conditions that let them in to begin with. A gap under a door or a crack in the foundation stays open the whole time, which means new individuals keep arriving even after a treatment clears out the current group. Exclusion work, physically closing off entry points, is what turns a recurring seasonal problem into a one-time fix. It’s also usually cheaper over time than paying for repeat treatments against the same entry point year after year.
Seasonal Patterns Worth Knowing
Fall
As outdoor temperatures drop, pests actively seek shelter, which is why fall is when homeowners in many regions see a spike in stink bugs, boxelder bugs, ladybugs, and mice all trying to get inside at once. Sealing entry points before the first cold snap makes a measurable difference, ideally in September or early October in most of the US and Canada, before overnight temperatures consistently drop below the point where these pests start actively seeking shelter.
Spring
Warming temperatures wake up overwintering insects and bring out new generations of ants and termites looking to establish colonies. This is the season to check for winged termite swarmers near foundations and window wells, and it’s also worth a fresh look at any exclusion work done the previous fall, freeze-thaw cycles over winter can reopen small gaps that were sealed months earlier.
Summer
Wasps and mosquitoes peak, along with increased ant activity as colonies forage more aggressively in the heat. Screens on windows and doors get more use during summer, which also means more wear, a torn screen that goes unnoticed for a few weeks is a common and easily missed entry point during this season specifically.
Winter and year-round patterns outside the US
In much of the UK, mild, damp winters mean rodents and some insects stay active and looking for shelter across a longer stretch of the year than in colder parts of North America. Australian homes, particularly in northern and coastal regions, deal with less of a hard seasonal cutoff altogether, which makes the exclusion walk-through below worth repeating more than once a year rather than treating it as a single fall task.
Doing an Exclusion Walk-Through
Walk the full perimeter of the house at ground level, then again looking at the roofline and soffits. Bring a flashlight and check gaps at dusk, when you can sometimes see daylight through a crack that’s otherwise hard to spot. Note anything that needs steel wool, caulk, or a repaired screen, and prioritize south and west-facing walls, which tend to see more pest activity due to warmth. A basic checklist helps: door sweeps intact, weatherstripping unbroken, no gaps around pipes or cables, vents properly screened, and no visible daylight through the foundation from inside a dark garage or basement.
Matching the Material to the Gap
Not every gap should be closed with the same product, and using the wrong one is a common reason exclusion work fails within a year. For gaps rodents might chew through, pack stainless steel wool or copper mesh into the opening first, then seal over it with caulk or expanding foam; foam and caulk alone are easy for a mouse to gnaw back open, but they generally won’t chew through metal mesh. For hairline foundation cracks under about a quarter inch, a paintable exterior-grade silicone or polyurethane sealant holds up better than acrylic latex caulk, which tends to shrink and crack within a couple of seasons. Larger foundation gaps, a half inch or more, usually call for hydraulic cement or a masonry patch rather than caulk, since caulk isn’t designed to bridge that kind of span. Vents and weep holes should get rigid quarter-inch hardware cloth rather than window screening, which insects and small rodents can push through or chew given enough time. Door sweeps come in a few styles: a basic vinyl sweep is the cheapest and easiest DIY fix, a brush-style sweep handles uneven thresholds better, and an aluminum sweep with a rubber gasket lasts the longest but costs more and is a bit more involved to install correctly.
On cost and timeline, a basic DIY exclusion pass, door sweeps, caulk, a few cans of foam, and some steel wool, typically runs under a hundred dollars in materials and can be done over a weekend for an average single-family home. A more thorough job that includes chimney capping, vent screening, and masonry repair on foundation cracks is a bigger undertaking and often makes more sense to hand off to a contractor or pest management company that does this kind of exclusion work regularly.
Mistakes That Undo Otherwise Good Exclusion Work
Painting over caulk before it’s fully cured is a common one, it can trap moisture underneath and cause the seal to fail early. Sealing a gap from the outside only, without checking whether insulation or wiring runs directly behind it, can also create hidden moisture problems if the gap was previously allowing airflow that kept that cavity dry. And a surprisingly common mistake is sealing gaps during the day and missing ones that only become obvious at dusk or under artificial light from inside, which is why the flashlight step in the walk-through above matters more than it sounds like it should.
What Not to Do
Don’t rely on caulk alone to seal a gap that rodents are actively using, mice can chew through caulk and even some foam sealants; steel wool packed into the gap before sealing is a better deterrent since they generally won’t chew through it. Don’t seal every exterior gap without checking for pests already living inside a wall void or attic first, trapping an active problem inside can create a bigger issue than the one you started with. And don’t treat exclusion as a one-time task and forget about it, seals degrade, caulk cracks, and screens tear, so an annual walk-through matters even after a thorough first pass.
DIY vs. Calling a Professional
Most of the entry points on the list above, door gaps, visible caulk failures, a torn screen, are reasonable DIY fixes with materials from any hardware store. Where it usually makes more sense to bring in a pest control technician is anything at height (roofline, soffits, chimney), anything where you’re already seeing droppings, gnaw marks, or nesting material inside a wall or attic, and any situation where you’ve sealed the visible gaps but the pest activity keeps coming back, which usually means there’s an entry point you haven’t found yet. A pest management company doing exclusion work will typically also check for interior signs you might not think to look for, like grease marks along baseboards or rub marks around a suspected rodent entry point, since those tell you whether a gap is actually in use before you spend time sealing it. If you’re unsure whether what you’re dealing with is worth a professional look, most companies, including ours, will do a free quote to walk the property with you before any work is scheduled.
A couple of common questions
How often should I redo the full walk-through? Once a year at minimum, ideally before fall, plus a quicker check in spring after winter’s freeze-thaw cycles. Homes in milder, wetter climates benefit from checking twice a year regardless of season.
Is it worth sealing gaps if I already have an active infestation? Yes, but pair it with treating what’s already inside first, or at least at the same time. Sealing alone on an active infestation stops new arrivals but does nothing about the pests already established behind your walls.
Will sealing every gap trap pests that are hibernating in the walls over winter? It’s a fair concern, but most overwintering insects like stink bugs and ladybugs are dormant enough that they won’t actively chew or claw their way further into living space, they’re more likely to show up sluggish on a windowsill on a warm winter day than to become a real problem. Rodents are the bigger exception; if you hear scratching in a wall before you seal up for the season, it’s worth confirming there’s nothing already inside before closing off every gap.
Does exclusion work affect a home’s energy bills? Often yes, and it’s a nice side benefit rather than the main point. The same gaps that let pests in are frequently the same ones letting conditioned air out, so a thorough sealing pass can measurably reduce drafts, particularly around utility penetrations and old weatherstripping.
When Exclusion Alone Isn’t Enough
If pests are already established inside wall voids or an attic, sealing the exterior traps the problem rather than solving it. That’s when it’s worth having a pest control contractor assess what’s happening on both sides of the wall. Call 1-844-783-4821 and we’ll help you figure out where the real entry points are and what’s already inside.
