How to Keep Stink Bugs Out of Your House: Seal These Entry Points

Stink bugs do not come inside to eat or breed. They come in to sleep through the winter, squeezing through gaps as thin as a credit card around windows, siding and attic vents when fall temperatures drop. That makes how to keep stink bugs out of your house mostly a sealing problem, not a spraying problem. Close the openings on the sunny south and west walls before late September, and you stop most of the invasion before it starts.

The work is ordinary weatherproofing: caulk, screens, door sweeps, vent covers and a careful look at the attic and soffits. Done once, it also cuts drafts and keeps out ladybugs, cluster flies, boxelder bugs and spiders. Any insecticide is a secondary step, and only when you follow the product label exactly.

If stink bugs are already inside, sealing still matters. Bugs overwintering in wall cavities often emerge indoors on warm winter days, and closing interior gaps around outlets, trim and light fixtures keeps them in the walls until spring, when they leave on their own.

How to Keep Stink Bugs Out of Your House Before Fall

Timing is everything. The brown marmorated stink bug starts looking for shelter when nights drop into the 50s °F, typically from mid-September through October in much of the country. They gather on warm, sunlit siding in the afternoon and crawl upward, probing every crack. Seal in late summer and you are ahead of them. Seal in November and you are sealing them in.

Walk the outside of the house on a sunny afternoon in early fall. Where you see bugs clustering, look closely for the gaps they are aiming for. That tells you which walls need the most attention.

Tools and Materials

• Exterior-grade silicone or siliconized acrylic caulk and a caulk gun
• Low-expansion spray foam for larger gaps (window-and-door formula)
• Copper mesh or stainless steel wool for stuffing gaps around pipes
• Replacement window screen, spline and a spline roller
• Door sweeps and adhesive-backed weatherstripping
• Fine insect mesh (about 1/16-inch) for vent and soffit openings
• Utility knife, putty knife and a stiff brush
• Stable extension ladder or step ladder, work gloves and safety glasses

Step 1: Caulk Windows, Trim and Siding Gaps

1. Inspect every window and door frame where the trim meets the siding. Old caulk often cracks and pulls away, leaving a thin slot that is perfect for stink bugs.
2. Scrape out failed caulk with a putty knife and brush the joint clean. Caulk will not bond to dust or loose paint.
3. Apply a continuous bead of exterior caulk along the top and sides of the trim. Leave weep holes at the bottom of window frames and siding open; they drain water and should not be sealed.
4. Check where siding meets the foundation, chimney and corner boards. Seal gaps along vertical trim with caulk. For gaps wider than about 1/4 inch, insert backer rod first.
5. Look behind fascia and at the ends of vinyl siding runs, where J-channel leaves openings. These are major entry points on the top of the wall.

Caulk works best between about 40°F and 90°F on a dry day. Check the tube for cure time before rain.

Step 2: Fix Screens and Window Seals

A single torn window screen can let in hundreds of bugs in one afternoon. Replace torn or loose screens, check that screen frames seat tightly in their tracks, and make sure window sashes close fully against their weatherstripping. Window air conditioners are a common gap; fill the space around the unit with foam insulation panels and seal the edges with removable weatherstripping tape.

Sliding patio doors deserve a close look too. The screen door often has a gap at the top or along the latch side. Adding a pile weatherstrip to the screen frame usually closes it.

Step 3: Install Door Sweeps and Weatherstripping

If you can see daylight under an exterior door, stink bugs can walk right in. A door sweep is the single most useful product here. Measure the door width, cut the sweep to length, and screw or stick it to the inside bottom of the door so the brush or rubber just touches the threshold when closed. Replace flattened weatherstripping along the door jambs, and adjust the threshold if it has an adjustable cap.

Garage doors need attention as well. Replace a cracked bottom seal and add brush seals to the sides if bugs are collecting inside the garage. The door between the garage and house should have a tight sweep and full weatherstripping.

Step 4: Screen Vents, Soffits and Attic Openings

Attics are where stink bugs congregate in the largest numbers. Gable vents, ridge vents, soffit vents and gaps where the roofline meets the wall all give them access. Cover gable vents from the inside with fine insect mesh, stapled to the framing. Check soffit panels for gaps or missing pieces, and replace damaged vent screens. Never block vents completely; attics need airflow to control moisture and heat.

Dryer vents, bathroom exhaust vents and kitchen range hood vents should have working dampers that close fully. Add a vent cover with a flap or louver if the damper sticks open. Do not put fine mesh over a dryer vent, because lint clogs it and creates a fire hazard.

Seal utility penetrations too. Stuff gaps around cable lines, hose bibs, AC line sets and gas meters with copper mesh, then caulk over the edge. Leave gas and electrical equipment itself to the utility or a licensed pro; only seal the gaps around the siding.

Ladder Safety for High Work

Much of this job happens above your head: fascia, soffits, gable vents and second-floor windows. Set extension ladders on firm, level ground at a 4-to-1 angle (1 foot out for every 4 feet up), extend them at least 3 feet above the roof edge if you are stepping off, and keep three points of contact. Never overreach; move the ladder instead. Avoid ladder work in wind, rain or near overhead power lines. For work on two-story walls, steep roofs or high gables, hire a professional with scaffolding or a lift. The savings are not worth a fall.

Using Insecticides Safely

When you think about how to keep stink bugs out of your house, exclusion does most of the work. If you choose to add an exterior insecticide barrier, pick a product labeled for stink bugs and for outdoor perimeter use, and follow the label exactly for where, when and how much to apply. The label is the law for pesticides. Wear the gloves, eye protection and respirator the label calls for, keep children and pets away until it dries, and never mix products together. Store chemicals away from pilot lights and heat sources if the product is flammable.

Indoor sprays are not recommended for stink bugs. Dead bugs inside walls attract carpet beetles that feed on them, and the chemicals add exposure in your living space. Vacuum indoor bugs with a dedicated shop vac or a hose with a nylon stocking trap, then empty it outside.

Troubleshooting

• Still finding bugs indoors in winter: they were already in the walls. Seal interior gaps around outlets, switch plates, recessed lights, ceiling fans and baseboards. For any electrical box, turn off the breaker and confirm power is off with a non-contact voltage tester before removing a cover plate, then install foam gaskets.
• Bugs clustered around one window: check behind the interior trim and at the sash pulley or balance pocket.
• Bugs in the attic every year: recheck gable vent mesh and look for gaps at the ridge cap or where dormers meet the roof.
• Caulk failed after a season: the joint moved too much. Use a higher-grade elastomeric sealant.

Cost and When to Call a Pro

Learning how to keep stink bugs out of your house is inexpensive. A DIY sealing kit of caulk, foam, door sweeps and mesh usually costs well under a couple hundred dollars for an average house. A pest control company or handyman offering exclusion work typically charges from a few hundred dollars for a basic seal-up to considerably more for extensive attic and roofline work.

Call a professional for multistory homes, steep roofs, recurring heavy infestations or older homes with suspect paint. If your home was built before 1978, test paint for lead before scraping around trim, and use lead-safe practices. Pros can also inspect siding and roof edges that are difficult to reach safely.