Most Boise-area homeowners don’t think about the crawl space until something goes wrong: a musty smell, scratching under the floor at night, or a spider-filled vent cover. But a crawl space is dark, sheltered and connected to the rest of the house through plumbing and wiring gaps, which makes it one of the easiest places for pests to settle in and move up from.
Here’s what lives in Treasure Valley crawl spaces, how they get in, and how pest control protects the space under your floors.
Why Pests Like Crawl Spaces
Crawl spaces stay sheltered from wind and weather, rarely get disturbed and often hold a bit of moisture from soil, plumbing or condensation. Insulation makes good nesting material. And because pipes, ducts and wires pass from the crawl space up into walls and cabinets, anything living down there has a route into the house.
Crawl Spaces and Treasure Valley Seasons
Our climate makes crawl spaces especially attractive at two points in the year. In fall, as nights get cold and nearby fields and open lots are cleared, mice look for warm, protected spots, and the space under a house is an easy choice. In the heat of July and August, the crawl space stays cooler than the outside air, which draws spiders and the insects they feed on. Many older homes in Boise, Nampa and Caldwell also have vents and access doors that have taken decades of weather, so worn screens and gaps are common.
Common Crawl Space Pests in the Treasure Valley
Mice and rats
House mice and, in some neighborhoods, rats move into crawl spaces as fields get harvested and temperatures drop in the fall. They nest in insulation, chew on wiring and ductwork, and travel up along pipes into kitchens and walls. Our rodent identification guide covers signs of each.
Spiders
Crawl spaces are prime habitat for spiders, including hobo spiders, giant house spiders and, in quiet, cluttered areas, black widows. They feed on the insects that also find their way in. See our spider identification guide.
Ants
Ants follow moisture, and crawl spaces near leaky plumbing or poor drainage can draw them in, sometimes as a route to the kitchen above.
Signs of Pests Under Your House
- Scratching or scurrying under floors, especially at night
- Musty or ammonia-like odors coming through floor vents
- Droppings near the crawl space access or on vapor barriers
- Torn or flattened insulation and displaced vapor barrier
- Heavy webbing around vents and the access door
- Gnawed wiring or ductwork
How Pests Get In
- Damaged or missing crawl space vent screens
- Gaps around plumbing, gas lines and electrical conduit where they pass through the foundation
- Cracks in the foundation and gaps under the access door
- Window wells and gaps where decks or porches meet the house
Mice can squeeze through very small openings, so a small gap is worth taking seriously. Our post on sealing a house against rodents goes into exclusion in more detail.
How Pest Control Protects a Crawl Space
Inspection
A technician checks vents, the access door, foundation walls, plumbing penetrations and the vapor barrier, looking for droppings, nesting, webbing and entry points.
Exclusion
Sealing gaps with durable materials like steel mesh and sealant around pipes and vents, and repairing screens, keeps rodents and many insects from getting in at all.
Rodent trapping
Traps placed along walls and travel routes in the crawl space catch mice and rats that are already inside, and checking them shows whether activity is dropping.
Spider and insect treatment
Treating the foundation, vents and entry points cuts down on the insects and spiders using the space, and knocking down webs helps show whether activity returns.
Ongoing service
Crawl spaces aren’t a one-and-done job. Seasonal pressure from mice in fall and spiders and ants in warmer months means regular service keeps problems from building up out of sight.
Cleaning Up Safely
If you find rodent droppings or nesting material, don’t sweep or vacuum it dry, which can stir up dust. The CDC’s guidance on preventing hantavirus explains how to ventilate, wet down droppings with disinfectant and clean up safely.
What Homeowners Can Do
- Check vent screens each fall and repair any damage
- Keep the access door closed and sealed
- Fix plumbing leaks and make sure gutters and downspouts carry water away from the foundation
- Keep stored items out of the crawl space, or in sealed plastic bins
- Keep firewood and woodpiles away from the foundation
Crawl Space Pest Control With ProGuard
Spiders, ants, mice and rats are core pests in our residential pest control, and we offer quarterly, bi-annual and one-time service. Rodent service is included at no extra cost with quarterly service plans; traps and materials are billed separately. Quarterly service plan customers also get free return visits.
ProGuard is based in Eagle and serves homes and businesses in Boise, Meridian, Nampa, Caldwell, Star, Middleton, Emmett and Garden City. Learn more about rodent control in Boise, call us at (208) 352-2062 or send us a message.