Treatment gets rid of pests that are already inside. Exclusion is what keeps new ones from getting in, and it’s often the step that gets skipped entirely. A home sealed well enough that pests can’t easily enter needs far less ongoing treatment, which saves money and reduces how much product goes down over time.
Start at the foundation
Cracks in a foundation, gaps around where pipes and cables enter the house, and unsealed weep holes in brick veneer are all common entry points. Weep holes are meant to let moisture escape, so they shouldn’t be sealed completely, but they can be fitted with mesh covers that block insects and rodents while still allowing drainage. Hairline foundation cracks are worth watching over time; a crack that widens season to season is worth a structural look regardless of pests, since it points to settling that will keep opening new gaps faster than you can seal them.
Doors and windows
A door sweep with a worn or missing gasket is one of the most common ways mice and insects get into a home, especially garage doors, which are frequently overlooked. Window screens with small tears are enough for flies and mosquitoes to get through, and a quarter-inch gap under an exterior door is enough for a mouse. Sliding glass doors deserve a specific check, since the brush seal along the bottom track wears down faster than a standard door sweep and is easy to forget because it’s low and out of sight.
Garage doors deserve extra attention beyond the bottom seal. The vertical seals along each side track and the small triangular gaps at the corners where the door meets the frame are common weak points that a homeowner checking only the bottom rubber gasket will miss entirely. A garage that’s attached to the house is effectively an extension of it as far as pests are concerned, so a well-sealed garage door does double duty, keeping pests out of the garage and out of the walk-in door that usually connects it to the living space.
Utility penetrations people forget
Beyond the obvious pipe and cable entry points, a handful of utility penetrations get missed on a typical walkthrough. Dryer vents with a damaged or missing flap let in insects and, in some cases, mice attracted to the residual warmth and lint. Exterior spigots and hose bib connections often have a gap behind the fixture itself, not just around the pipe, that’s easy to overlook because the fixture visually looks sealed from a few feet away. Cable and satellite lines run into a home through a small drilled hole that’s rarely caulked properly by the installer, and AC line sets running from an outdoor condenser to an indoor unit pass through a wall penetration that’s a similarly common, easily overlooked gap.
Rooflines and vents
Roof rats and squirrels often enter through gaps where a roofline meets a wall, damaged fascia boards, or attic vents without proper mesh. Chimneys without a cap are an open invitation for birds, raccoons, and squirrels looking for a denning site. Checking these areas from the ground with binoculars, or having a pest professional check them, catches problems before an animal moves in. Bathroom and kitchen exhaust vents that exit through the roof or a wall should have a functioning damper or flap; a stuck-open flap is a surprisingly common entry point that doesn’t get checked until something’s already living behind it.
Landscaping choices matter
- Keep mulch a few inches away from the foundation rather than piled against the siding
- Trim tree branches back from the roofline so they aren’t a bridge for rodents and ants
- Keep firewood stacked away from the house and off the ground
- Address standing water near the foundation, which draws both insects and the pests that feed on them
- Keep dense groundcover and ivy trimmed back from exterior walls, since it holds moisture against siding and gives pests cover right up to the building
Materials that actually hold up
Not every sealant is equal to the job. Caulk is fine for small, stable gaps that don’t flex, but it isn’t chew-resistant, so it won’t stop a mouse or rat on its own. Steel wool or copper mesh packed into a gap before caulking over it gives you both a physical barrier and a weatherproof finish. For larger openings around vents or pipes, hardware cloth screwed into place holds up to both weather and gnawing far longer than foam.
A basic toolkit for a DIY exclusion pass
Most exclusion work doesn’t require specialty equipment. A caulking gun with an exterior-grade, paintable silicone caulk handles most stable gaps, while steel wool and copper mesh, sold in most hardware stores for this exact purpose, cover anything that needs to resist chewing. Hardware cloth with a small enough mesh size, a quarter-inch or smaller, blocks entry for everything from mice down to larger insects, and a few stainless outdoor screws are usually enough to mount it over a vent opening. For most homes, a weekend and well under a hundred dollars in materials covers the majority of what a first exclusion pass turns up; it’s the labor of finding and reaching every gap, not the cost of materials, that takes the real time.
A seasonal exclusion routine
Spring is the best time to check what winter’s freeze-thaw cycle opened up, since expanding ice is one of the most common causes of new foundation and masonry cracks. Late summer into early fall is the highest-priority window for exclusion work overall, since it’s the window before rodents start actively looking for a way indoors ahead of colder weather. A full pass twice a year covers most of what a home needs.
How to actually walk the exterior
Start at one corner of the house and work your way around methodically rather than jumping between spots, so you don’t miss a section. Get down low enough to check foundation level, not just eye level, since that’s where most rodent and insect entry points sit. Bring a flashlight for shaded areas under decks and behind shrubs, and a small notepad or your phone to log what you find, since it’s easy to spot three or four issues on a walk and only remember to fix one of them afterward.
A note on older homes
Homes built before modern sealing standards were common often have more gaps by default, not because anything is wrong with the construction, but because the materials and code requirements from decades ago simply didn’t prioritize this the way current building practice does. If you’re in an older home and this is the first time you’ve done a real exclusion pass, expect to find more than you would in new construction, and don’t be discouraged if the first walkthrough turns into a longer project than you expected.
What not to seal
Not every gap should be closed completely. Weep holes, as mentioned above, need mesh rather than a solid seal so moisture can still escape brick veneer. Foundation vents in a crawlspace serve an airflow purpose and generally need a screen rather than a full block, otherwise you risk trapping moisture that causes its own problems. When in doubt about whether an opening serves a structural or ventilation purpose, it’s worth checking before you caulk it shut, since undoing a mistake here can cost more than the original pest risk would have.
When exclusion is a job for a professional
A lot of exclusion work is genuinely DIY-friendly, but a few situations are worth handing to a pest professional. Rooflines and chimney work often mean ladder access at height, which carries its own risk regardless of pest concerns. An active infestation already inside a wall or attic changes the sequencing entirely, since sealing an entry point before confirming what’s already inside can trap animals in the structure rather than keeping them out of it. And a home with widespread, unclear gaps, especially an older home where it’s hard to tell which openings are actually being used, benefits from a professional inspection that can prioritize the handful of entry points that matter most instead of trying to seal everything at once.
Why this step gets skipped
Exclusion work is slower and less visible than spraying, and it takes an eye trained to notice a gap that’s been there for years without causing a problem, until conditions change and something finds it. It’s also one of the more effective long-term investments a homeowner can make, because it reduces pressure on every pest at once rather than targeting one species at a time.
A couple of quick questions
How do I know if a gap is actually being used, or just a gap? Look for grease marks, droppings, gnaw marks, or shed insect skins right at the opening, and check for cobwebs across the gap, which is actually a good sign, since an undisturbed web means nothing has passed through it recently. A gap with none of these signs is still worth sealing preventively, but it’s not necessarily an active entry point.
Will sealing my home completely eliminate the need for any pest treatment? Exclusion dramatically reduces pest pressure but rarely eliminates it entirely, since some pests, like certain ants and spiders, can still establish outdoors close to the structure regardless of how well-sealed the building itself is. What a good exclusion pass does is reduce how often and how aggressively you need to treat, not replace treatment altogether.
Natural Pest Solutions includes exclusion recommendations as part of how we approach every property, not as an upsell after the fact. Closing the gaps a pest is actually using, combined with natural-first treatment, is what makes a plan hold over time instead of needing to be repeated every few months.
