Sealing Your Home Against Bugs: A Room-by-Room Exclusion Guide

Bugs don't appear in a house at random — they follow specific entry points and are drawn in by specific conditions, and both are fixable without a single pesticide. Exclusion, done room by room, does more long-term good than almost anything else you can do.

The exterior perimeter

Start outside, since this is where most entry points live. Check where utility lines, cables, and pipes pass through the exterior wall — these penetrations are rarely sealed as tightly as the wall around them, and a bead of silicone caulk closes the gap permanently. Check the bottom of exterior doors for a worn or missing door sweep; a quarter-inch gap under a door is a wide-open lane for crawling insects. Foundation cracks deserve the same caulk treatment, especially anywhere a crack is wide enough to see daylight through.

Basements and crawl spaces

Moisture is the single biggest driver of pest activity in a home, and basements and crawl spaces are where it usually starts. A running dehumidifier keeps humidity down where silverfish, sowbugs, and other moisture-loving bugs would otherwise thrive. Firewood stored against an exterior wall is worth moving at least 20 feet away and up off the ground — it's both a food source and a direct bridge for wood-dwelling pests, and stacking it against the house undoes a lot of the other sealing work.

The kitchen and pantry

Indoors, the kitchen is where food-seeking bugs concentrate. Store dry goods — flour, cereal, pet food — in airtight containers rather than their original cardboard or paper packaging; pantry moths and flour beetles can chew directly through a cardboard box but not through sealed plastic or glass. Wipe up crumbs and spills the same day rather than the same week, and don't leave pet food out overnight.

Attics and upper floors

Window and door screens with even a small tear are an open invitation to flying insects, and a patch kit fixes one in minutes. Attics are where overwintering bugs — cluster flies, ladybirds, boxelder bugs — end up gathering in fall, having entered through soffit vents or small gaps under the roofline; a quick check of vent screens before autumn is worth the ten minutes it takes.

Storage areas everywhere

Stacked cardboard boxes are both food and shelter for silverfish, roaches, and carpet beetles alike. Swapping cardboard for sealed plastic storage bins in basements, attics, garages, and closets removes both problems at once, and it's one of the highest-value five-minute changes available.

Bathrooms and garages

Bathrooms combine two conditions bugs like at once: consistent moisture from showers and sinks, and small gaps around pipe penetrations under the vanity. Silverfish in particular gravitate toward bathrooms for exactly this reason, grazing on the starches in wallpaper paste, bar soap, and shampoo residue. A bathroom fan run long enough after showering to actually clear the humidity, plus a caulked gap under the sink, addresses most of it. Garages are worth a separate pass too — the gap under an overhead door is typically far larger than any other entry point in the house, and a garage door weather seal closes it in under an hour.

It's worth revisiting these same rooms on a schedule rather than once and forgetting about it. A door sweep compresses over time and stops sealing as tightly as it did new, caulk can crack or shrink away from a gap after a few seasons of temperature swings, and a garage weather seal wears fastest of all given how often the door cycles open and closed. An annual walk-through with the same checklist you used the first time catches this kind of gradual failure before it reopens an entry point you'd already dealt with.

Laundry rooms, mudrooms, and home offices

A few rooms get skipped in most exclusion checklists simply because they don't fit neatly into "wet room" or "storage area," but each has its own quiet risk factor. Laundry rooms combine a water supply line, a drain, and often a floor-level dryer vent to the outside — all three are potential entry points, and the dryer vent in particular should have an intact flapper or screen, since a stuck-open one is a direct, unobstructed tunnel to the outdoors. Mudrooms and entryways see the heaviest door traffic in the house, which means door sweeps here wear out faster than anywhere else and are worth checking more often than the twice-yearly schedule suggested for the rest of the house. A home office is low-risk on its own, but stacks of paper, cardboard file boxes, and rarely-moved furniture against an exterior wall recreate the same clutter-and-shelter conditions that make storage areas attractive to silverfish and roaches, just in a room nobody thinks to check.

Worked example: what the checklist actually scores

To make the scoring concrete: a home with damp basement conditions and visible exterior gaps checked off — and nothing else — scores 6 out of a possible 17, landing in the Moderate band, with two recommendations returned (fix the moisture, seal the gaps). Add wood-to-soil contact, food debris left out, and cardboard clutter in storage areas to that same list and the score climbs to 12, crossing into the High band with five active recommendations. Check off every single factor on the list and the score reaches the full 17, the Severe band. The point of walking through the numbers isn't the exact score — it's seeing that two of the eight factors (moisture and exterior gaps) are weighted highest at three points each, so fixing those two first moves the score more than fixing any other three factors combined.

Timing the work to the season

Sealing work isn't equally urgent year-round. Late summer, ahead of the fall gathering of overwintering bugs described elsewhere on this site, is the highest-leverage window for exterior gap-sealing and vent-screen checks specifically, since it heads off the season when boxelder bugs, cluster flies, and stink bugs are actively searching for a way in. Spring is the better time to focus on foundation and wood inspection instead, since that's when subterranean termite swarms peak in many regions. Our Seasonal Pest Calendar breaks this down by month if you'd rather plan around what's actually active right now than follow a generic twice-a-year rule.

Renting? What's still worth doing

Most of this list doesn't require permission to fix. A door sweep, a portable dehumidifier, airtight storage bins, and screen repair tape are all things a renter can buy and use without touching anything structural or requiring a landlord's sign-off, and together they cover a meaningful share of the highest-value items above — moisture control and gap-sealing at the level of a door or a window, specifically. Caulking a foundation crack or replacing an exterior door sweep permanently is a different category of work, and it's reasonable to flag those to whoever's responsible for the building rather than doing it yourself, especially if the gap is large enough to see daylight through. Either way, the same checklist applies; it's only the "who does the work" part that changes, and a landlord is generally more responsive to a specific, described gap than a vague complaint about seeing bugs.

What sealing actually prevents, and what it doesn't

It's worth being precise about what exclusion work does. Sealing gaps and controlling moisture stops new bugs from getting in and removes the conditions that let a population grow once it's there — that covers the overwintering nuisances, most fabric and stored-food pests, and a meaningful share of structural risk. What it doesn't do is remove an infestation that's already established somewhere sealing can't reach, like a mature termite colony already feeding inside a wall or a carpet beetle population already established deep in stored textiles. In those cases, exclusion is still worth doing — it stops the situation from getting worse and prevents a repeat once it's resolved — but it's a prevention measure being layered onto an existing problem, not a fix for one on its own.

If you only have five minutes

Not every gap gets sealed in one sitting, and that's fine — the factors aren't weighted equally, so a short list still captures most of the benefit. In order of impact: check for standing moisture in the basement or crawl space and address any active leak first, since it's the single highest-weighted factor on the checklist. Next, run a hand along the bottom of every exterior door feeling for daylight or a draft, since a worn door sweep is cheap and fast to replace. Third, glance at where any visible pipe or utility line passes through an exterior wall for an unsealed gap. Those three checks alone address the two highest-weighted risk factors and take well under the five minutes suggested, even if the rest of the room-by-room list waits for another day.

Turning this into a plan

Rather than trying to remember all of this, our Infestation Risk Checklist turns these same factors into a scored checklist — check off what applies to your home and get a weighted risk band plus the specific fixes worth prioritizing first, starting with whichever carry the most weight for your situation.