How to Get Rid of Spiders in the Basement (Without Chemicals)

Walk into your basement, flip on the light, and there they are: webs in the ceiling corners, a spider scuttling behind the water heater, maybe an egg sac tucked into a dark crevice. Basement spiders are one of the most common homeowner complaints — and also one of the most solvable without a single drop of pesticide.

Here’s the perspective shift that makes this guide work: spiders are predators, not invaders. They’re in your basement because their prey is there — flies, silverfish, crickets, and other basement insects. A basement full of spiders is a basement with a food supply and the damp, cluttered, undisturbed conditions spiders love. Remove the conditions and the prey, and the spiders leave on their own.

Nearly all common basement spiders in North America — cellar spiders, common house spiders, wolf spiders that wander in — are harmless to people and pets. This guide shows you how to clear them out and keep them out using only physical and environmental methods.

Know What You’re Dealing With

Cellar spiders (the long-legged ones)

Pale, with extremely long thin legs and small bodies, hanging upside-down in messy webs in ceiling corners. Completely harmless. They actually hunt and eat other spiders, including more concerning species.

Common house spiders

The classic cobweb builders — round-bodied, brownish, building tangled webs in corners, behind boxes, and under stairs. Harmless.

Wolf spiders (the ground hunters)

Larger, hairy, fast runners that don’t build webs — they chase prey on foot. They wander into basements from outside, especially in fall. Their appearance is alarming but they’re not aggressive and bites are rare.

When to take it seriously

The vast majority of basement spiders are harmless. The exceptions worth knowing: black widows (shiny black with a red hourglass marking, in dark undisturbed areas) and brown recluses (violin marking, in specific regions). If you suspect either, don’t handle them — photograph from a safe distance and consider professional identification. For everything else, the methods below are all you need.

Step 1: Clear the Current Population (No Chemicals)

The web-removal sweep

1. Take a microfiber duster with an extendable handle or a broom wrapped in a damp cloth, and systematically sweep every ceiling corner, wall-ceiling joint, window frame, and behind-pipe gap in the basement.
2. Removing webs does more than clean — it destroys egg sacs and forces spiders to expend energy rebuilding, which discourages them from staying.
3. Work top to bottom: ceilings first, then walls, then behind and under everything.

Catch and release

• For individual spiders, the cup-and-card method works perfectly: cup over the spider, card underneath, release outside away from the house.
• A vacuum with a hose attachment handles spiders in hard-to-reach spots — behind the furnace, under stairs, inside wall voids via gaps. Empty outside immediately.
• Check and remove egg sacs — small silk balls in webs or tucked into crevices. Each sac can hold dozens to hundreds of spiderlings. Vacuum them up; don’t just knock them down (they’ll hatch where they land).

Repeat monthly

One thorough sweep rarely gets everything. Repeat the web-removal sweep monthly for 2–3 months — each round catches the next generation before it establishes.

Step 2: Run a Dehumidifier (The Foundation of Prevention)

Spiders themselves aren’t strongly moisture-dependent — but their prey is. Silverfish, crickets, centipedes, and sowbugs all thrive in damp basements, and where prey thrives, spiders follow. Dry the basement and you starve the spiders out indirectly.

• Keep basement humidity at 40–50% with a properly sized dehumidifier.
• Fix any water intrusion: seal foundation cracks, make sure gutters direct water away, check the sump pump.
• Repair plumbing drips — even a slow leak creates a permanent insect oasis.

This single step, maintained year-round, does more for long-term spider control than any spray ever could.

Step 3: Declutter (Remove Their Real Estate)

Spiders need undisturbed hiding spots. Basements are often full of them:

• Move stored items off the floor onto shelving or pallets, and away from walls by a few inches — this eliminates the dark wall-floor gap spiders love.
• Replace cardboard boxes with sealed plastic bins — cardboard provides both shelter and (as it softens with dampness) food for the insects spiders eat.
• Clear out unused items, old newspapers, fabric piles, and anything you haven’t touched in a year.
• Keep the area around the furnace, water heater, and laundry clear — warmth plus clutter is prime spider habitat.

Step 4: Cut Off Their Food Supply

No prey, no spiders. Address the basement insects spiders are feeding on:

• Silverfish and firebrats: the dehumidifier plus decluttering handles most of these.
• Crickets: seal entry points and dry things out (see our cricket guide linked below).
• Flies and gnats: fix moisture sources, clean floor drains, don’t leave organic debris around.
• Outdoor lighting: insects gather at basement window lights, and spiders build webs where insects gather. Switch to yellow “bug” bulbs or motion-sensor lights near basement windows.

Step 5: Seal Entry Points

Most basement spiders either come from outside or from wall voids. Seal the routes:

• Repair basement window screens and add weatherstripping.
• Caulk gaps around pipes, vents, and cables entering the basement.
• Seal foundation cracks with concrete caulk.
• Install door sweeps on the basement door and any exterior doors.
• Check where the sill plate meets the foundation — gaps here are a major spider highway from wall voids.

Natural Deterrents: What Actually Helps (and What Doesn’t)

Let’s be honest about the popular remedies:

• What helps modestly: strong-smelling essential oils (peppermint, tea tree, eucalyptus) sprayed or wiped along baseboards and entry points can deter spiders from specific spots. The effect is real but short-lived — reapply weekly. Chestnuts and hedge apples (osage orange) are folk remedies with no reliable evidence; skip them.
• What helps a lot: everything in Steps 1–5 above. Environmental control beats repellents every time.
• What doesn’t help: ultrasonic pest repellers. Multiple studies have found no meaningful effect on spiders. Save your money.

If you use essential oils, keep them away from cats — several common oils (tea tree, peppermint, citrus) are toxic to cats even in small amounts.

Why You Shouldn’t Spray for Basement Spiders

It’s tempting to reach for a can of spider spray, but consider:

• Sprays don’t reach them. Residual sprays work when insects walk across treated surfaces — but web-building spiders sit in their webs and rarely contact treated areas.
• You’ll kill the wrong things. Broad sprays kill the harmless cellar spiders that were eating the actually annoying pests.
• The webs remain. Dead spiders in webs still look like a spider problem, and new spiders will recolonize the same undisturbed corners within weeks.
• Chemical exposure without benefit. Basements often house HVAC equipment that circulates air through the whole home — not the place for unnecessary pesticide.

Physical removal plus environmental control is faster, safer, and longer-lasting. Save insecticides for pests where they’re actually effective.

Maintaining a Spider-Free Basement

• Monthly: quick web sweep of ceiling corners during the warm months.
• Year-round: keep the dehumidifier running at 40–50% humidity.
• Fall: check door sweeps, window screens, and foundation sealing before spiders (and their prey) move indoors for winter.
• Ongoing: keep clutter off the floor and away from walls; address any new moisture immediately.

Frequently Asked Questions

Are basement spiders dangerous?

The common ones — cellar spiders, house spiders, wolf spiders — are not dangerous to people or pets. Learn to recognize black widows and brown recluses if they’re reported in your region, but don’t assume every spider is a threat.

Why are there so many spiders in my basement all of a sudden?

A sudden increase usually means a prey population boomed — often after a damp spell brings in silverfish, crickets, or flies. Fix the moisture and the prey, and spider numbers fall.

Do spiders come back to the same webs?

Yes — established spiders maintain and repair webs in productive spots. That’s why repeated web removal works: it makes the location unprofitable and they relocate.

Will getting rid of spiders cause other bugs to increase?

Temporarily, possibly — spiders do provide free pest control. But the environmental fixes in this guide (drying, decluttering, sealing) reduce the prey insects too, so you’re not trading one problem for another.

How do I keep spiders out of basement windows?

Repair screens, switch nearby lighting to yellow bug bulbs or motion sensors, and sweep webs from window frames monthly. Spiders build where insects gather — reduce the insects and the spiders follow.

📚 Sources & Further Reading

• NPIC: Minimizing Pesticide Exposure
  Practical tips on choosing lower-toxicity products, protective equipment, and keeping children and pets safe from the National Pesticide Information Center (Oregon State University & U.S. EPA).

🚨 If someone ingests a pesticide or shows poisoning symptoms, call Poison Control immediately: 1-800-222-1222 (U.S.).

Related Guides

• How to Get Rid of Silverfish in the Bathroom — eliminating a favorite spider prey species with the same dehumidifier strategy.
• Is Pest Control Safe for Pets? — why the no-chemical approach in this guide is the safest option around animals (including essential-oil cautions for cats).
• Fall Home Maintenance Checklist — the seasonal sealing routine that keeps spiders and their prey outside.
• How to Get Rid of Crickets in the Basement for Good (7 Methods) — getting rid of basement crickets.
• Musty Smell in the Basement? How to Find and Fix the Cause — finding the moisture source behind basement pests.