Why Is My House Full of Spiders?

Reviewed 2026-07-30 · How we research

Most likely causes of a house full of spiders, ranked

1. 1. An insect food supply inside the house

   Most common — the entire reason they stay

   Cellar spiders, house spiders and jumping spiders establish where prey is dense: near lights, around drains that produce drain flies, in basements with springtails and pillbugs, and in garages with moths. A web that stays occupied for weeks means it is catching enough to be worth defending.

   10-minute self-test: Look at the webs, not the spiders. Webs full of insect husks mean a strong indoor prey population. Empty webs abandoned after a few days mean the spiders are just passing through.

2. 2. Outdoor lighting drawing insects to the walls

   Very common and the easiest big win

   White and blue-rich lights (cool-white LED at 5000K, mercury vapor, standard porch bulbs) attract far more night-flying insects than warm amber sources. Insects mass on the siding, spiders set up around the door, and then both come in. Switching to 2200–2700K warm LEDs or true amber bug bulbs measurably reduces insect accumulation.

   10-minute self-test: Stand outside 30 minutes after dark and look at the wall around each exterior light. Heavy insect density plus webs at the fixture confirms it. Turn that light off for three nights and see whether the webs go unused.

3. 3. Gaps at doors, windows, vents and utility penetrations

   Common

   A spider needs surprisingly little clearance. Worn door sweeps, torn screens, unscreened soffit and foundation vents, and unsealed gaps around hose bibs and cable entries are the standard routes. Garage doors with degraded bottom seals are the single busiest entry in most homes.

   10-minute self-test: Close every exterior door and look for daylight along the bottom and sides at midday. Press a dollar bill in the door and pull — if it slides out freely, the seal is not sealing.

4. 4. Clutter, storage and undisturbed voids

   Common in basements, garages and crawlspaces

   Cardboard boxes, stacked firewood, and stored items against walls create the dark, undisturbed harborage that reclusive species prefer. Brown recluse in particular favors cardboard, which resembles the loose bark of their natural habitat.

   10-minute self-test: Place a few sticky monitor traps flat against walls behind stored items and check weekly. Which traps fill tells you which zone is harboring them, and it also gives you a specimen to identify.

5. 5. Seasonal mate-seeking movement in late summer and fall

   Predictable and temporary

   In August through October, mature male spiders wander looking for females. This is why big spiders sprint across the floor in the evening in fall and why the population seems to spike without any change in your house. It subsides on its own.

   10-minute self-test: Note the season and the behavior. A large spider moving fast in the open in September is a wandering male, not an infestation.

What it costs to fix a house full of spiders

DIY fixes for a house full of spiders

• Change the porch light color temperature

  Swap cool-white bulbs for 2200–2700K warm LEDs or amber bug bulbs, and put lights on motion sensors so they are not burning all night. Fewer insects means fewer spiders within a week or two.

• Vacuum webs and egg sacs, then empty the canister outside

  One egg sac can hold 100–400 eggs. Removing sacs is worth more than killing adults. Do it weekly for a month and the indoor population drops sharply.

• Replace the garage door bottom seal

  It is the most-used entry in the house and a 20-minute job. While you are there, seal the gap where the door track meets the frame.

• Get storage off the floor and out of cardboard

  Sealed plastic totes on shelving eliminate the harborage that cardboard provides. In brown recluse territory, this is the single most effective non-chemical measure.

• Move woodpiles and dense plantings away from the wall

  Six feet minimum for firewood, and keep a clear, dry band along the foundation. Both reduce the insect population feeding the spiders.

• Use sticky traps along walls, not in the middle of the room

  Spiders travel along edges. Traps placed flush against baseboards catch many times more than traps in open floor.

Where homeowners waste money on a house full of spiders

• Ultrasonic spider repellers. Repeatedly tested, repeatedly shown to do nothing.
• Chestnuts, peppermint oil sprays and other folk remedies. There is no controlled evidence they reduce spider populations.
• Fogging a basement. Spiders are on webs above the fog and largely unaffected.
• Broad insecticide spraying as a spider fix while the porch light still attracts a swarm of insects every night.

When to call a pest control operator about a house full of spiders

Why Is My House Full of Spiders — questions homeowners ask

Sources used for a house full of spiders

• University extension entomology — spider identification and management
• CDC / NIOSH — venomous spiders (black widow, brown recluse)
• Research on light spectrum and nocturnal insect attraction (amber vs. cool-white)
• FTC — enforcement on ultrasonic pest repeller claims