Direct answer: If a squirrel chewed wires in the attic, assume the cable is unsafe until proven otherwise. The right first move is to shut off the affected circuit if you can identify it safely, stay out of the damaged area, and get an electrician involved for any exposed, nicked, or partly severed wiring.
Most likely: Most often, you will find tooth marks on NM cable, missing insulation, exposed copper, or a dead light or receptacle on the same run. Even small-looking chew damage can arc later after the animal is gone.
Rodent damage in an attic is not a cosmetic problem. A squirrel can strip insulation off a cable, nick a conductor just enough to heat up under load, or leave damage hidden under loose insulation. Reality check: a wire can look only lightly chewed and still be unsafe. Common wrong move: covering the spot with electrical tape and calling it fixed.
Don’t start with: Do not start by taping over the bite marks, twisting wires back together, or energizing the circuit to see what still works.
The outer cable jacket has tooth marks, shredded plastic, or bare copper showing where the squirrel worked on it.
Start here: Start by shutting off the suspected circuit and checking whether the damage is only on the outer jacket or reaches the insulated conductors underneath.
A breaker started tripping after attic noise, nesting, or visible animal activity.
Start here: Treat that as active electrical damage, not a nuisance trip. Leave the breaker off and inspect only from a safe distance without moving insulation around.
There is a sharp electrical smell near the attic hatch, ceiling, or a room below the attic run.
Start here: Stop using that circuit immediately. This can mean arcing or overheated damaged insulation, and it needs urgent electrician service.
A light, smoke alarm, fan, or a few outlets quit working while the rest of the house still has power.
Start here: Check the breaker first, then assume a damaged attic cable is possible if the outage lines up with known squirrel activity overhead.
This is the most common attic animal damage. Squirrels often gnaw the sheath first, especially on exposed runs near rafters or entry points.
Quick check: With power off, look for rough tooth marks, missing jacket, and yellow, white, or orange NM cable with shredded outer covering.
Once the animal gets past the jacket, the individual hot or neutral conductor can be cut or partly exposed. That can cause tripping, dead circuits, or heat under load.
Quick check: Do not touch the cable. Use a flashlight and look for colored conductor insulation cut open or bare copper visible inside the damaged section.
If the circuit stayed energized after the chewing, the damaged section may have started arcing, especially where copper is exposed or nearly severed.
Quick check: Look for black soot, melted insulation, a sharp burnt-plastic smell, or brittle darkened cable around the bite marks.
The visible chew spot is not always the only one. Squirrels tend to travel the same path and may damage several sections on one branch.
Quick check: From a safe walkway or hatch view, scan the cable route for more chew marks, nesting material, droppings, or repeated gnawing near entry holes.
With animal-damaged wiring, the first job is reducing shock and fire risk, not figuring out every bad spot right away.
Next move: The area is de-energized or isolated, and you can do a careful visual check without adding more risk. If you cannot identify the circuit safely, or the main panel situation is unclear, stop and call an electrician.
What to conclude: A safe shutdown tells you whether this is a controlled inspection or an urgent live hazard.
A scuffed outer jacket is bad enough to need repair, but conductor damage raises the risk sharply and changes how urgent the fix is.
Next move: You can tell whether the damage is limited to the outer sheath or has reached the actual conductors. If the cable disappears under insulation or the damage is partly hidden, assume it may be worse than it looks and leave the circuit off.
What to conclude: Any cut into the inner conductor insulation, exposed copper, or partly severed wire means the cable needs professional repair or replacement, not a patch job.
Matching the attic damage to the house symptoms helps confirm that this is the active fault and not just old chew marks on an unused run.
Next move: You have a clearer map of what that cable serves and how serious the failure is. If the symptoms do not line up cleanly, there may be additional hidden damage or another unsafe electrical problem nearby.
Attic branch wiring repairs often require replacing a damaged cable section, adding accessible junction boxes where allowed, and checking the rest of the run for hidden chew points. That is electrician work.
Next move: The repair gets scoped correctly the first time, and the electrician can bring the right materials for cable replacement or accessible splice repair. If you cannot get same-day help and the circuit feeds something critical, use temporary extension-cord workarounds only in occupied spaces and only if they do not create a trip hazard or overload.
Even after the animal is gone, damaged insulation and nicked copper can fail later when the circuit is loaded again.
A good result: You avoid a repeat failure and reduce the chance of hidden heat damage getting buried again under insulation.
If not: If the breaker cannot stay off, the panel labeling is wrong, or more circuits seem involved, get urgent electrician service rather than more homeowner troubleshooting.
What to conclude: The job is not finished when the squirrel leaves. It is finished when the damaged wiring is repaired, verified, and protected from another round of chewing.
No. Tape is not a safe repair for chewed house wiring. If the jacket or inner conductor insulation is damaged, the cable needs proper electrician repair or replacement.
Even if the inner wires are not obviously exposed, the cable still needs a proper evaluation. Small tooth marks can hide deeper damage, and attic heat makes marginal insulation problems worse over time.
Not if you already know the cable was chewed. Re-energizing damaged wiring can create arcing, heat, or a breaker trip. Leave it off until the wiring is checked and repaired.
Coverage varies a lot by policy and cause of loss. Take photos, document what lost power, and ask your insurer what they require before cleanup or repair starts.
It is still urgent. A cable can be damaged enough to fail later under load even if the circuit seems normal right now. The safe move is to keep that circuit off if possible and get it inspected promptly.
If the wiring is damaged, start with the electrician because the immediate risk is electrical. Pest exclusion matters too, but you do not want new or repaired wiring left energized around active damage.