Basements and garages share characteristics that attract pests: they tend to be cooler, more humid, less frequently cleaned, and more cluttered than living spaces. They also have more entry points — garage doors, foundation cracks, utility penetrations, and floor drains. These spaces serve as both entry points for pests coming from outside and as habitat for pests that prefer undisturbed, damp environments.
Common Basement and Garage Pests
Spiders
Basements and garages are prime spider habitat. Dark corners, undisturbed storage areas, and steady insect prey create ideal conditions. Common basement spiders include cellar spiders (daddy longlegs), wolf spiders, and in some regions, brown recluse spiders.
Management:
- Declutter and organize — spiders thrive in undisturbed spaces with lots of hiding spots
- Store items in sealed plastic bins rather than cardboard boxes
- Vacuum webs, egg sacs, and spiders regularly, paying attention to corners, ceiling joists, behind shelving, and along window wells
- Reduce the insect population (spider food) — address moisture, seal entry points, and use sticky traps
- Diatomaceous earth applied along baseboards, in cracks, and around foundation perimeters can kill spiders that walk through it
- Sticky traps (glue boards) placed along walls catch wandering spiders and help monitor activity levels
- In regions where brown recluse spiders are established, sticky traps are particularly important for monitoring — see the spider control page for species-specific information
Mice and Rats
Garages and basements are the most common rodent entry points in homes. Garages in particular are vulnerable because of the large door opening, stored pet food and bird seed, and gaps around utility connections.
Management:
- Seal gaps around the garage door perimeter — bottom seals, side seals, and where the frame meets the wall
- Seal utility penetrations (pipes, wires, exhaust vents) with steel wool and caulk
- Install 1/4-inch hardware cloth over foundation vents
- Store all food (including pet food, bird seed, and grass seed) in sealed metal or heavy plastic containers — not bags
- Keep garbage in sealed metal cans
- Reduce clutter and storage at floor level — elevate stored items on shelving where possible
- Set snap traps along walls and behind storage items if signs of activity appear
- Do not use poison bait in garages where pets have access
- See the mice and rats page
Centipedes
House centipedes are common in basements. They are fast-moving, multi-legged predators that feed on spiders, insects, and other arthropods. While startling in appearance, they are generally beneficial — a house centipede in the basement is eating other pests.
According to the University of Kentucky Entomology Department, house centipedes are indicative of other pest populations. If centipedes are numerous, there is a significant prey population (insects, spiders) to support them.
Management for those who prefer fewer centipedes:
- Reduce moisture — centipedes are strongly attracted to damp environments
- Use a dehumidifier to keep basement humidity below 60%
- Fix leaks and improve ventilation
- Seal cracks and gaps in the foundation and around windows
- Reduce the insect prey population through general IPM practices
- Sticky traps along walls catch centipedes effectively
Millipedes
Millipedes are not insects — they are multi-legged arthropods that feed on decaying organic matter. They occasionally enter basements in large numbers during heavy rain or drought, seeking moisture or drier conditions respectively.
- Millipedes do not bite, damage structures, or reproduce indoors
- Reduce moisture around the foundation
- Seal foundation cracks and gaps under doors
- Remove leaf litter, mulch, and debris from immediately around the foundation
- Large migrations are temporary and typically resolve within a few days
Silverfish
Silverfish are small, silver-gray, wingless insects that prefer cool, damp environments. They feed on starchy materials — paper, book bindings, wallpaper paste, photos, and some textiles. Basements with stored books, papers, and boxes are ideal silverfish habitat.
Management:
- Reduce humidity with a dehumidifier
- Store papers, books, and photos in sealed plastic bins
- Use diatomaceous earth in cracks, along baseboards, and behind shelving
- Remove old cardboard boxes (silverfish eat the starch in cardboard)
- Seal cracks in walls and floors
Earwigs
Earwigs occasionally enter basements and garages through foundation cracks, drawn by moisture. They are harmless to humans despite the pincers (which are used for mating rituals and defense against other earwigs). They feed on decaying plant material and some small insects.
- Reduce moisture and debris around the foundation exterior
- Seal entry points
- Rolled newspaper or damp cardboard traps placed overnight along walls — earwigs shelter inside and can be disposed of in the morning
Crickets
Field crickets and camel crickets (cave crickets) enter basements and garages, particularly in fall. Camel crickets are common in damp basements and feed on organic material including fabric, paper, and other stored items.
- Reduce moisture
- Seal entry points
- Sticky traps along walls catch both species effectively
- Reduce outdoor harborage — leaf litter, mulch, and ground cover near the foundation
Moisture Control: The Foundation of Basement Pest Management
Moisture is the single most important factor for basement pest problems. Reducing moisture addresses centipedes, silverfish, earwigs, crickets, millipedes, and mold (which itself attracts pests like booklice and mold mites).
Dehumidification
According to the University of Nebraska-Lincoln Extension, maintaining basement humidity below 60% (ideally 40-50%) significantly reduces moisture-loving pest populations.
- A dehumidifier is the most direct solution for damp basements
- Empty or auto-drain the dehumidifier regularly
- Monitor humidity with a hygrometer (inexpensive and available at hardware stores)
Drainage and Waterproofing
- Ensure gutters and downspouts direct water away from the foundation (extend downspouts at least 4-6 feet from the house)
- Grade soil away from the foundation so water does not pool against the wall
- Address any water intrusion — seeping walls, floor cracks with moisture, standing water after rain
- Consider interior or exterior waterproofing for basements with chronic moisture issues
Ventilation
- Ensure basement and crawl space ventilation meets building code requirements
- Exhaust fans in attached garages reduce moisture and fumes
- Open windows during dry weather when practical
Organization and Storage
How basements and garages are organized directly affects pest pressure:
- Use sealed plastic bins for all storage. Cardboard boxes attract silverfish, provide rodent nesting material, and create hiding spots for all insects
- Elevate storage off the floor using shelving or pallets. Floor-level storage creates undisturbed habitat for pests and makes inspection difficult
- Leave space between storage items and walls — allows inspection and air circulation, and reduces harborage
- Declutter regularly — stored items that are never accessed become permanent pest habitat
- Avoid storing food in basements or garages unless in pest-proof containers. Pet food bags, bird seed, and grass seed stored in bags are rodent magnets
Exclusion for Basements and Garages
These spaces typically have more entry points than any other area of the home:
- Foundation cracks — fill with hydraulic cement for structural cracks, caulk for cosmetic cracks
- Gaps around pipes and utility lines — steel wool and caulk, copper mesh for rodent exclusion
- Garage door seals — bottom, sides, and top seals all need to be intact
- Window wells — cover with hardware cloth or clear plastic covers
- Floor drains — cover with fine mesh screens (prevents sewer roach entry)
- Gaps where the sill plate meets the foundation — a common but often overlooked entry point
- Exterior wall vents — cover with 1/4-inch hardware cloth
Diatomaceous Earth Application
Basements and garages are ideal locations for diatomaceous earth because the powder can be applied and left undisturbed for long periods:
- Apply thin layers along baseboards, behind shelving, around foundation perimeters, and in cracks
- Apply in crawl spaces and unfinished areas where it will remain dry
- Reapply if moisture compromises the powder
- DE works against ants, cockroaches, silverfish, earwigs, centipedes, and other crawling pests
For serious infestations, consult a licensed pest control professional.