How do I keep roaches, crickets, and silverfish out of my house?

Dehumidify basements and crawlspaces below 50% relative humidity, fix plumbing leaks and insulate sweating pipes, dry sink and counter surfaces nightly, and seal cracks around baseboards, utility penetrations, and the foundation. These pests all depend on dampness to some degree, so removing it is more durable than any spray, and it prevents the population from establishing rather than just reacting to it.

What humidity level should I actually target?

Below 50% relative humidity indoors, with the EPA's broader recommendation of staying below 60% throughout the home. Silverfish specifically need humidity above 75% to reproduce and their eggs fail below 50%, which is why a basement consistently above roughly 60% is inviting enough on its own to sustain silverfish, crickets, and earwigs together, even without any other attractant present. A digital hygrometer removes the guesswork about where your basement actually sits.

Does moisture control actually work, or do I still need to spray?

For roaches, crickets, silverfish, and earwigs, correcting the moisture source is the durable fix — spraying without it treats the symptom while the conditions that keep drawing pests back stay in place, so the same problem tends to resurface within weeks. Extension guidance is consistent that insecticides indoors are actively discouraged for these moisture-driven pests; find and eliminate the dampness instead, and treat any spray as a short-term supplement at most, not the solution.

What attracts these pests to a home in the first place?

Dampness above all — a basement or crawlspace over roughly 60% relative humidity, sweating pipes, slow leaks, and poor grading around the foundation are the common thread across nearly every pest on this page. Roaches add food residue and crumbs to that list, since they forage using surface moisture and food access at night, which is why sanitation matters alongside drying the space out; neither lever alone fully solves a roach problem the way it does for silverfish.

Should I spray indoors for silverfish or earwigs?

No — extension guidance discourages indoor insecticide use for these moisture pests specifically, since it doesn't address why they're there in the first place. The more effective and lasting approach is finding and correcting the humidity source: a dehumidifier, fixed leaks, and improved crawlspace or basement ventilation address the actual reason they're present, rather than killing the individuals you can see while the underlying damp conditions stay exactly the same for the next generation.

How do I prevent termites without a full treatment?

Keep untreated wood at least 18 inches and treated wood at least 6 inches above soil grade, maintain a roughly 10-inch inspection gap between siding and mulch or soil so mud tubes stay visible, direct drainage and irrigation away from the foundation, and fix leaks promptly. This meaningfully reduces risk, but confirmed termite activity — mud tubes, swarmers, damaged wood — needs a licensed inspection, since soil-applied treatment is regulated, specialized work.

Why do camel crickets keep showing up in my basement?

Camel crickets are essentially a living moisture indicator — University of Maryland Extension notes that seeing a lot of them in a basement usually points to an unresolved moisture problem rather than a cricket problem specifically. Solving the dampness with a dehumidifier and leak repairs typically resolves the crickets as a side effect, without needing to target the crickets directly.

How close can wood be to the soil around my foundation?

Untreated wood should stay at least 18 inches above soil grade, and treated wood at least 6 inches, per Missouri Extension guidance on subterranean termite prevention — closer than that and the wood has direct or near-direct access to soil moisture termites rely on. Beyond that spec, keep roughly 10 inches of clearance between siding and mulch or soil so any termite mud tubes remain visible during a routine walk around the house each spring.

Are thrips actually a household pest I need to prevent?

Thrips are primarily an outdoor plant pest that occasionally wanders indoors, often arriving on a new houseplant or flying in through standard window screens, which are wide enough that thrips pass through them without much trouble. Quarantining new houseplants for one to two weeks before placing them near other plants is the main, evidence-based prevention step, rather than home-sealing or spraying, which isn't the effective lever for a pest this small and mobile.

Are these pests actually harmful, or just a nuisance?

Mostly a nuisance, with two exceptions worth taking seriously. Termites cause real structural damage over time if left unaddressed, which is why confirmed activity warrants a professional inspection. The rest — roaches, crickets, silverfish, earwigs — are primarily a nuisance and occasional allergen source, best resolved by removing the moisture and food access that draws them rather than treating them as a health emergency.

PreventionCommon Household Pests

Common Household Pest Prevention: Dry It Out, Seal It Up

TL;DR

One variable drives this entire everyday indoor mix — roaches, crickets, silverfish, earwigs, and termites — more than any other: moisture. Dehumidifying below 50% relative humidity and fixing leaks is rated HIGH-VALUE and durable because it removes the root cause rather than the symptom. The one exception is termites: moisture reduction genuinely helps prevent them, but confirmed activity needs a licensed inspection, not a DIY spray.

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NH License #782664Family-owned since 2017Updated Jul 2026

The humidity target
Below 50% relative humidity indoors (EPA recommends below 60%)
Better Termite (citing EPA humidity guidance) — the shared threshold for silverfish, roaches, crickets, and earwigs.
Silverfish reproduction threshold
Need humidity above 75% to reproduce; eggs fail below 50% RH
Better Termite silverfish control guidance.
Why roaches forage at night
German cockroaches routinely access surface moisture during nighttime foraging
NC State Extension — German Cockroach Surveillance and Management; drying sink/counter surfaces nightly removes that access.
The "living moisture meter" pest
Camel crickets in a basement usually point to an unresolved moisture problem
University of Maryland Extension — crickets.

The honest verdict

Does this actually work?

HIGH-VALUE and durable because it attacks the root cause rather than the symptom, but slower than spraying and, for termites specifically, only a risk-reduction measure — confirmed activity still needs a licensed inspection and treatment.

Works — High

Evidence: Multiple extension sources link silverfish, camel crickets, and German cockroaches directly to ambient moisture and document 50% RH as the shared threshold below which these pests struggle to persist or reproduce. Missouri Extension documents the same moisture dependency for subterranean termites, which require soil contact specifically for hydration.

Works when

Basement and crawlspace humidity is kept below 50% relative humidity with a dehumidifier
Leaks are fixed and sweating pipes insulated promptly
Wood-to-soil clearance (18in untreated, 6in treated) and a 10-inch inspection gap are maintained around the foundation
Sink and counter surfaces are dried nightly and food residue cleaned up

Fails when

Indoor insecticides are used instead of correcting the moisture source
A basement stays above roughly 60% relative humidity despite occasional dehumidifier use
Wood, mulch, or debris is left in direct contact with the foundation
Confirmed termite mud tubes or swarmers are treated with a DIY spray instead of a licensed inspection

At a glance

Different bugs, same root cause: dampness

How it works

Easy DIY

Moisture control removes the shared condition nearly every pest in this group depends on: dehumidifying basements and crawlspaces below 50% relative humidity, fixing leaks, and improving drainage denies roaches, crickets, silverfish, and earwigs the dampness they need, while also directly reducing termite risk by removing wood-to-soil moisture contact. Sanitation and sealing add a second layer, especially for roaches, which also forage on food residue.

Vital stats

Time: A weekend to install a dehumidifier and complete an initial sealing pass; ongoing monthly humidity monitoring
Best for: NH homes with damp basements, crawlspaces, or fieldstone foundations — which describes a large share of the state's older housing stock.
Cost: Low for caulk and a hygrometer; moderate for a basement dehumidifier; termite inspection and any soil treatment is a licensed-professional cost

German, American, and Oriental cockroaches, house and camel crickets, silverfish, earwigs, and even subterranean termites don't have much in common at a glance — but nearly all of them are chasing the same thing: moisture. A basement or crawlspace that stays damp is inviting to every pest on this list, and University of Maryland Extension goes so far as to call camel crickets a "living moisture meter" — see a lot of them, and you almost certainly have an unresolved leak or humidity problem, not just a bug problem.

That's genuinely useful, because it means one lever — drying the space out — does most of the prevention work across this entire group, instead of needing a different spray for each pest. Sanitation and sealing matter too, especially for roaches, but moisture correction is the fix that actually lasts. Termites are the honest exception: reducing moisture and wood-to-soil contact meaningfully lowers your risk, but if you find active mud tubes or swarmers, that's a licensed-inspection call, not a DIY one — soil-applied termiticide treatment is specialized, regulated work.

Step by step

How to do it

Install a dehumidifier and target below 50% RH
Set up a dehumidifier in the basement or crawlspace and monitor relative humidity with a digital hygrometer, aiming to keep it below 50%.
Tip: A reading consistently above 60% is enough on its own to sustain silverfish, crickets, and earwigs together — that's your signal to run the dehumidifier harder.
Fix leaks and insulate sweating pipes
Repair plumbing leaks, insulate cold-water pipes that sweat in warm weather, and make sure gutters and grading direct water away from the foundation.
Caution: A single unfixed leak under a sink or in a crawlspace can undo hours of dehumidifier work.
Dry sink and counter surfaces nightly
Wipe down sink and counter surfaces before bed, since German cockroaches routinely forage using overnight surface moisture.
Tip: Pair this with clearing crumbs and food residue — roaches respond to both moisture and food access.
Maintain termite wood-to-soil clearance
Keep untreated wood at least 18 inches and treated wood at least 6 inches above soil grade, and maintain roughly a 10-inch inspection gap between siding and mulch or soil.
Tip: Walk this inspection gap each spring looking for mud tubes — catching activity early is far cheaper than catching it late.
Seal cracks around baseboards and utility penetrations
Caulk cracks around baseboards, window casings, foundation, and utility penetrations with silicone or acrylic-latex caulk, and screen vents.
Tip: Focus first on cracks near known damp areas — that's where roaches and crickets are already searching for a way in.
Vacuum regularly and store textiles sealed
Vacuum floors, closets, and baseboards regularly, and store off-season clothing, linens, and paper goods in sealed plastic bins rather than cardboard.
Tip: Dispose of vacuum bags after a heavy cleanup rather than reusing them — some fabric-pest eggs can survive inside.
Quarantine new houseplants
Keep any new houseplant separate from your other plants for one to two weeks before moving it into the main collection, to catch thrips or other hitchhiking pests before they spread.
Tip: Screens alone won't stop thrips — they're small enough to pass through standard window mesh, so quarantine is the more reliable lever.

What you need

Tools & materials

Dehumidifier
Keep basement and crawlspace humidity below the level that sustains this pest group
Target below 50% RH; run continuously through humid summer months
Digital hygrometer
Monitor relative humidity so dehumidifier use is targeted, not guesswork
Check monthly at minimum, more often in summer
Silicone or acrylic-latex caulk
Seal cracks around baseboards, window casings, foundation, and utility penetrations
Prioritize cracks near damp areas first
Pipe insulation
Prevent condensation on cold-water pipes that feeds moisture pests
An often-overlooked source inside under-sink cabinets
Vacuum
Remove lint, food residue, and fabric-pest eggs from floors and closets
Dispose of bags after a heavy cleanup
Sealed plastic storage bins
Replace cardboard storage that fabric pests and moisture can penetrate
Use for off-season clothing, linens, and paper storage

Stay safe

Safety first

General
Low risk
Avoid indoor insecticides for silverfish, crickets, and earwigs — these are moisture-driven pests, and correcting the dampness is the effective, extension-recommended fix.
General
Caution
Confirmed termite activity (mud tubes, swarmers, damaged wood) should go to a licensed applicator rather than a DIY soil treatment — termiticide application is specialized, regulated work under RSA 430.
Applicator
Caution
Crawlspace access for moisture repair and inspection can involve confined-space and electrical hazards near a sump pump or wiring — proceed carefully or hire a pro for extensive work.
General
Low risk
If any pest-control product is ever ingested or causes irritation, contact the Northern New England Poison Center at 1-800-222-1222, available 24/7.

Avoid these

Common mistakes

Why this method fails in practice.

Spraying indoors for moisture pests instead of correcting the humidity source
Letting a basement sit above 60% relative humidity despite owning a dehumidifier
Leaving wood, mulch, or debris in direct contact with the foundation
Treating confirmed termite mud tubes with a DIY spray instead of getting a licensed inspection
Storing textiles and paper in cardboard instead of sealed plastic bins
Skipping the new-houseplant quarantine and introducing thrips directly to an established collection

New Hampshire context

Moisture-driven pest prevention in New Hampshire

New Hampshire's abundant older housing stock — damp fieldstone and rubble foundations, uninsulated crawlspaces, settling sill plates — is the single biggest driver of this group's pressure statewide, which is exactly why moisture control, not sealing or spraying, is the lead lever on this page. UNH Cooperative Extension names termites alongside carpenter ants as the state's most troublesome structural pests, underscoring that the same damp conditions feeding silverfish and crickets in your basement can also be feeding a termite colony near your foundation. This page covers year-round indoor nuisances; for fall overwintering invaders like stink bugs and boxelder bugs, see the separate Household Pests prevention page — the two are kept deliberately distinct.

Peak season

Year-round; basement humidity peaks in summer, termite swarms typically appear in spring

First-frost anchor: Manchester first hard frost ~Oct 19 (50%) / Oct 29 (80%) per NOAA 1991-2020 — clear gutters and grade soil away from the foundation before the frost to prevent the snowmelt moisture surge that fuels spring pest pressure

Dehumidifying, sealing, and sanitation are DIY-legal statewide with no pesticide license required. Soil-applied termiticide treatment is specialized work typically requiring a licensed applicator under RSA 430/NHDAMF.

UNH Cooperative Extension identifies termites, alongside carpenter ants, as New Hampshire's most troublesome structural pests — reinforcing why moisture correction is the shared, durable fix across this entire pest group.

This method targets

Pests this applies to

Eastern Subterranean Termite

Thrips

When to call a pro

General Pest Control with Anchor

Moisture correction resolves most of this group on its own, but termite activity specifically is not a DIY-treatable problem once confirmed, and recurring roach or silverfish activity despite dehumidifying often points to a hidden leak worth a professional eye. Anchor's General Pest Control service combines moisture-focused prevention with licensed termite inspection where needed.

Call us when…

You find mud tubes, swarmers, or damaged wood suggesting active termites
Roaches, crickets, or silverfish persist despite dehumidifying and sealing
You can't locate the moisture source despite a full basement inspection
A vulnerable household wants professional confirmation before relying on DIY moisture fixes alone

General Pest Control

free inspection; same-day service across southern and central New Hampshire.

Get a free inspection Learn about the service

Keep them out

Keep basements and crawlspaces below 50% relative humidity year-round
Maintain proper wood-to-soil clearance and a visible inspection gap around the foundation
Fix leaks and insulate sweating pipes as soon as they're found, not on a seasonal schedule

Common questions

Frequently asked

Sources & further reading(9)

[1]
Better Termite — Silverfish Control
Below-50% RH target, EPA below-60% recommendation, silverfish 75%+ RH reproduction threshold
industryverified 2026-07-13
[2]
ExterminateK — Professionally Recommended Solutions for Eliminating Moisture Bugs
Basement humidity above ~60% inviting silverfish, sowbugs, earwigs, house centipedes, and springtails together
industryverified 2026-07-13
[3]
NC State Extension — German Cockroach Surveillance and Management
Nighttime surface-moisture foraging behavior; moisture and sanitation as primary control levers
extensionverified 2026-07-13
[4]
Penn State Extension — Got Roaches? Eliminate Roaches with IPM
Moisture control, sealing, and sanitation as an integrated roach-prevention approach
extensionverified 2026-07-13
[5]
University of Maryland Extension — Crickets
Camel crickets as a basement moisture indicator; dehumidifying as the resolving fix
extensionverified 2026-07-13
[6]
NC State Extension — Camel Crickets
Exclusion and harborage-reduction guidance for camel crickets
extensionverified 2026-07-13
[7]
Missouri Extension — Subterranean Termites (G7420)
Wood-to-soil clearance specs (18in untreated / 6in treated), 10-inch inspection gap, drainage guidance
extensionverified 2026-07-13
[8]
UNH Cooperative Extension — Carpenter Ants Fact Sheet
Termites named alongside carpenter ants as NH's most troublesome structural pests
extensionverified 2026-07-13
[9]
University of Minnesota Extension — Managing Insects on Indoor Plants
Thrips as an outdoor plant pest that wanders indoors via houseplants
extensionverified 2026-07-13

Written & reviewed by

Verified

Daniel Brady

NH-Licensed Pesticide Applicator · License #782664 (NHDAMF, RSA 430)

Daniel Brady is the New Hampshire–licensed applicator behind Anchor Pest Services, a family-owned pest control company serving the Manchester area since 2017.

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Anchor Pest Services

When common household pests won't quit, we will.

Same-day service across Southern New Hampshire. NH-licensed #782664. Family-owned since 2017. We diagnose the pest, then treat it the right way — with a satisfaction guarantee.

Get a free inspection Call (603) 785-0118

Keep Exploring

Common Household Pest Prevention: Dry It Out, Seal It Up

Works when

Fails when

Different bugs, same root cause: dampness

How it works

How to do it

Install a dehumidifier and target below 50% RH

Fix leaks and insulate sweating pipes

Dry sink and counter surfaces nightly

Maintain termite wood-to-soil clearance

Seal cracks around baseboards and utility penetrations

Vacuum regularly and store textiles sealed

Quarantine new houseplants

Tools & materials

Dehumidifier

Digital hygrometer

Silicone or acrylic-latex caulk

Pipe insulation

Vacuum

Sealed plastic storage bins