Sowbugs end up inside your house because they’re searching for moisture, and they almost always die quickly once indoors. These small, flat, gray crustaceans are completely harmless to people, food, furniture, and your home’s structure. But if you’re seeing them regularly, it’s a reliable signal that you have a moisture issue or an unsealed entry point worth fixing.
What Sowbugs Are (and Aren’t)
Sowbugs are terrestrial crustaceans, more closely related to shrimp and crabs than to any insect. They’re small, oval, gray or brown, and covered in segmented plates. You’ll often see them confused with pillbugs (roly-polies), but the two are easy to tell apart. Sowbugs have a flatter body and two small tail-like appendages sticking out from their rear end. Pillbugs are rounder and curl into a tight ball when disturbed. Sowbugs can’t roll up at all. If you nudge one and it scurries away instead of curling, it’s a sowbug.
They’re nocturnal and spend daylight hours hiding in damp, dark spots. Outdoors, that means leaf litter, mulch piles, under stones, flowerpots, and rotting wood. They feed on decaying organic matter and pose zero threat to you or your belongings.
Why They’re Coming Inside
Sowbugs are heavily reliant on ambient humidity to survive. They breathe through gill-like structures that need to stay moist, so dry indoor air is essentially lethal to them. They’re not trying to infest your house. They’re wandering in from the damp perimeter around your foundation, drawn by moisture gradients, and typically ending up in basements, crawl spaces, and ground-level floors.
The two things that bring sowbugs indoors are moisture near your foundation and gaps that let them in. If you’re finding them occasionally, a few likely wandered through a crack under a door. If you’re finding them frequently, something more systematic is going on: a drainage problem saturating the soil near your foundation, a leaky basement, excessive mulch piled against the house, or gaps around pipes and windows that make entry easy.
Without high moisture, sowbugs find it almost impossible to survive indoors. Most die within a day or two. The ones you find dead on your basement floor or in a bathroom corner didn’t establish a colony. They dried out.
Fixing the Moisture Problem
Since moisture is the single factor driving sowbugs toward your home, reducing it around your foundation is the most effective control. Start outside:
- Clear organic debris near the foundation. Pull back mulch, leaves, and plant debris from the base of your house. These materials trap moisture and create ideal sowbug habitat right next to your walls.
- Remove hiding spots. Stones, firewood stacks, flowerpots, and landscape timbers sitting against the foundation all harbor sowbugs. Move them several feet away.
- Fix drainage. Make sure gutters, downspouts, and splash blocks are directing water away from the house, not pooling it near the foundation. Grade the soil so water flows outward.
- Don’t overwater. Garden beds and planters right next to the house keep the soil saturated. Water in the morning so the area dries during the day.
Inside, address any dampness in basements and crawl spaces. A dehumidifier can help, but fixing the source of moisture (leaking pipes, poor ventilation, water seeping through foundation walls) is the real solution. If your crawl space has exposed dirt, a vapor barrier can significantly reduce humidity.
Sealing Entry Points
Even with moisture under control outside, sowbugs will still wander in if they can find a gap. A crack as small as 1/16 of an inch is enough for insects and small crustaceans to squeeze through. Focus on these areas:
Check the bottoms of all exterior doors, especially the corners, which are the most common entry points. Install door sweeps or thresholds if light is visible under the door. For sliding glass doors, line the bottom track with foam weatherstripping. Garage doors should have a rubber bottom seal (vinyl tends to crack in cold weather and create gaps).
Caulk cracks around windows, doors, and fascia boards using silicone or acrylic latex caulk. Latex caulk is easier to work with since it cleans up with water and can be painted over. Clean out old peeling caulk before applying fresh material for a better seal.
Seal utility openings where pipes and wires enter your foundation and siding. This includes outdoor faucets, electrical receptacles, gas meters, dryer vents, and cable lines. Depending on the size of the gap, you can use caulk, expandable foam, cement, or copper mesh. For crawl space and foundation vents, install quarter-inch wire mesh hardware cloth to block entry while maintaining airflow.
Do You Need Pesticides?
In most cases, no. Fixing moisture and sealing gaps solves the problem permanently because sowbugs simply can’t survive in a dry, sealed house. Spraying pesticides indoors is unnecessary since the sowbugs are already dying on their own from dehydration. Just vacuum up the ones you find.
If you want an extra layer of protection and the sealing work feels overwhelming, an exterior barrier treatment with a liquid insecticide can help. Apply it at the base of exterior doors, around foundation vents and utility openings, and in a band two to six feet wide along the ground around the foundation perimeter and two to three feet up the foundation wall. Synthetic pyrethroid products sold for home perimeter use are the standard option. This is a supplement to sealing and moisture control, not a replacement for it.
Sowbugs in Houseplants
Potted plants are another common source. Sowbugs thrive in the moist soil of indoor and outdoor containers, feeding on decaying roots and organic matter in the potting mix. If you’re finding sowbugs near your houseplants, tip the plant out of the pot, scrape off the old soil, and repot with fresh potting mix. This eliminates both the sowbugs and any eggs in the soil without chemicals.
Plants brought in from a porch or patio for winter are especially likely to carry sowbugs along. Inspecting the soil surface and the drainage holes before bringing pots inside can prevent a surprise appearance later.