Yes, and the bill can be bigger than people expect. Rats and mice chew wiring, pipes, wood and car parts, shred insulation for nests and contaminate whatever they live in. The expensive part is usually not the gnawing you can see but the cleanup, rewiring and insulation work once an infestation has been going for a while. Homeowners insurance usually won't pay for it. This guide covers what rodents actually damage, what repairs cost in real reported quotes, what insurance does and doesn't cover, and how to keep the bill small.
Yes. University of California IPM lists the damage: rats gnaw electrical wires and wooden structures, shred insulation in walls and ceilings for nests, can chew soft metals like copper and lead, and Norway rats can undermine foundations and slabs by burrowing. Roof rats in an attic raise "safety concerns (electrical sparks and fires)."
The costs that hurt are cleanup and repairs. Homeowners report quotes of about $6,500 to $10,000 for attic infestations that needed the insulation replaced, and up to $10,000 for car wiring harnesses. Most homeowners policies exclude damage from rodents, so catching activity early is what keeps the bill small.
Why Rodents Damage Everything
A rat's or mouse's front teeth never stop growing. The Internet Center for Wildlife Damage Management says a Norway rat's incisors grow about five inches a year, and the rat keeps them worn down by gnawing on hard surfaces. UC IPM notes rats can chew through plastic, foam, wood and caulk, which is why spray foam alone doesn't keep them out.
You can tell who did the chewing by the marks. ICWDM puts mouse gnaw marks at about 1/32 inch wide and rat marks at about 1/16 inch, and mouse entry holes are usually 1-1/2 inches across or less.
What Rats and Mice Damage, and What It Costs
| Damage | What happens | Reported costs |
|---|---|---|
| Attic insulation | Shredded for nests, tunneled through, soiled with urine and droppings | One homeowner was quoted about $7,000 for rat removal, insulation replacement and a wiring check. Another was quoted $6,489.99 for attic insulation work and about $10,000 in all (Reddit) |
| Electrical wiring | Insulation chewed off, exposing conductors. UC IPM lists fire and spark risk | Varies with how much has to be rewired and where the damage is |
| Car wiring | UC IPM says rats commonly gnaw engine wire insulation, causing malfunctions and "expensive mechanical repairs" | From $600 to $800 for repairs up to dealer quotes of $9,000 to $10,000 for replacement harnesses (Reddit) |
| Plumbing and gas lines | Rats chew soft metals like copper and lead, plus plastic. UC IPM warns they "may even chew directly on natural gas lines" | Water damage from a chewed line can exceed the pipe repair |
| Foundations and slabs | Norway rat burrows can undermine foundations and slabs (UC IPM) | Depends on the structural repair |
| Doors, trim and stored items | Gnawing on doors, ledges, corners, boxes and stored food | Mostly replacement of what's chewed and contaminated |
One caution on insulation: not every quote is necessary. When a technician told one homeowner the attic insulation had to be replaced, a commenter replied that in a vented attic it didn't need to be, and in another thread the top reply to an $18,000 insulation quote from a pest company was to get quotes from insulation contractors instead. Ask to see the damage and get a second opinion on big jobs.
Can Mice and Rats Cause Electrical Fires?
They can create the conditions for one. When rodents chew the insulation off wires, bare conductors can short or spark, and nests of shredded paper and insulation often sit right beside the wiring. UC IPM lists electrical sparks and fires as a safety concern when roof rats live in an attic.
You'll often see the claim that rodents cause 20% to 25% of house fires of "unknown origin," usually credited to the National Fire Protection Association. We couldn't find that figure in any NFPA publication. Where it appears in print, it's framed as "it has been estimated," with no primary source, so treat it as unverified. The real risk doesn't need the statistic: any chewed wiring is worth having an electrician check.
Does Insurance Cover Rodent Damage?
- Homeowners insurance: usually not. The Insurance Information Institute says a standard policy "will not cover damage due to lack of maintenance, mold or infestation from termites or other pests." Insurance professionals on Reddit say the same: damage from "insects, birds, rodents or vermin" is usually excluded. Some policies cover secondary damage, such as water damage from a chewed pipe, so read your policy and ask your agent.
- Car insurance: often yes, with comprehensive coverage. Several insurance commenters, including one who said they were an auto adjuster, said rodent damage to car wiring is normally covered under comprehensive, unlike homeowners policies.
- Renters: damage to your belongings depends on your renters policy. Report rodents to your landlord in writing. In North Carolina, a rat infestation caused by structural defects is listed as an imminently dangerous condition the landlord must repair.
Signs Damage Is Already Happening
- Droppings along walls, in cabinets, in the attic or garage
- Gnaw marks on wood, wiring, pipes or stored boxes, and fresh shavings of wood or insulation, which ICWDM says indicate active infestation
- Scratching or running sounds in walls or ceilings at night
- Grease rub marks along beams, pipes and wall edges where rodents travel
- Flattened or tunneled insulation in the attic
- Electrical problems: flickering lights, dead outlets or a warning light on the car dashboard
For help telling them apart, see signs you have rats in your walls at night.
How to Keep the Damage Small
- Act on the first signs. One mouse or a few droppings is a small job. A months-old attic population is a cleanup project.
- Seal entry points with the right materials. UC IPM says to seal openings larger than 1/4 inch with steel wool, wire screen or sheet metal, since rats chew through plastic, foam, wood and caulk. See how mice get into your house and the gaps to seal.
- Remove food and shelter. Store food and pet food in sealed containers, clear clutter in attics and garages, and keep woodpiles away from the house.
- Trap indoors rather than poisoning. Rodents that die from bait inside walls or attics can leave odor and flies behind.
- Get chewed wiring checked by an electrician, and have gnawed gas lines checked right away.
- Clean up safely. Don't sweep or vacuum droppings. The CDC recommends wetting them with a bleach solution first and wiping up with paper towels while wearing gloves.
Our rodent control service handles inspection, sealing and trapping across South Carolina, North Carolina and Virginia. If you're deciding between doing it yourself and hiring help, see DIY vs. professional rat and mouse extermination.
Key Takeaways
- Rats and mice chew wiring, wood, plastic, foam, insulation and soft metals, and Norway rats can undermine foundations.
- Reported repair quotes run about $6,500 to $10,000 for attic cleanups and up to $10,000 for car wiring harnesses.
- The "25% of unexplained fires" statistic is unverified, but chewed wiring is a real fire risk.
- Homeowners insurance usually excludes rodent damage. Car comprehensive coverage often covers chewed wiring.
- Early action keeps it cheap: seal gaps with metal, remove food and trap at the first signs.
Frequently Asked Questions
Yes. They gnaw electrical wires, wood, plastic and soft metals, shred attic and wall insulation for nests, contaminate what they live in, and Norway rats can undermine foundations and slabs by burrowing. Homeowners report quotes of about $7,000 to $10,000 for attic infestations that needed cleanup and new insulation.
They can create the conditions for one by chewing the insulation off wires, often next to flammable nest material. UC IPM lists electrical sparks and fires as a safety concern when rats live in an attic. The often-quoted figure that rodents cause 20% to 25% of fires of unknown origin has no primary source we could find.
Usually not. The Insurance Information Institute says standard policies don't cover damage from infestation by pests, and most policies exclude damage from rodents and vermin. Some cover secondary damage, such as water damage from a chewed pipe, so check your policy.
Often, if you have comprehensive coverage. Insurance professionals commonly describe rodent damage to car wiring as a covered comprehensive loss, unlike on homeowners policies. Check your own policy and deductible.
It depends on your policy, and it would apply to your belongings, not the building. Report rodents to your landlord in writing. In North Carolina, a rat infestation caused by structural defects is an imminently dangerous condition the landlord must repair.
Gnaw marks on wood, wiring, pipes and boxes, fresh shavings of wood or insulation, droppings, grease rub marks along walls and beams, and flattened or tunneled insulation. Rat gnaw marks are about 1/16 inch wide and mouse marks about 1/32 inch.
They can chew through many building materials, including wood, plastic, foam and caulk, and soft metals like copper and lead. That's why gaps should be sealed with steel wool, wire screen or sheet metal rather than foam alone.
Not always. It depends on how much is soiled, shredded or tunneled. Ask to see the damage, and for large insulation jobs get quotes from insulation contractors as well as the pest company. Contaminated insulation should be handled with CDC-style precautions, not swept or vacuumed dry.
Act at the first signs, seal openings larger than 1/4 inch with metal-based materials, store food and pet food in sealed containers, clear clutter and woodpiles, trap indoors, and have any chewed wiring checked by an electrician.
Sources: UC IPM, Pest Notes: Rats, Publication 74106; Internet Center for Wildlife Damage Management, Norway Rats and House Mice; Insurance Information Institute, Which disasters are covered by homeowners insurance?; J. Auerbach, "Does New York City really have as many rats as people?", Significance (2014); N.C. Gen. Stat. § 42-42; CDC, How to Clean Up After Rodents; homeowner and insurance-professional accounts from Reddit (via Google search excerpts).
Photo credits: Chuck Homler d/b/a Focus On Wildlife, CC BY-SA 4.0, via Wikimedia Commons; NY State IPM Program at Cornell University, CC BY 2.0, via Wikimedia Commons.