Chewed Wiring and Fire Risk

Why they chew cable

It Is Not About Eating It

Squirrels have incisors that grow continuously and have to be worn down. Gnawing is maintenance, not appetite, and it is directed at whatever is the right hardness — which is why cable sheathing, plastic pipe, conduit and structural timber all get chewed by an animal that has no interest in any of them as food.

Cable is particularly attractive because it is the right diameter to work on and it runs conveniently along the timbers they are already travelling on. A squirrel does not seek out your ring main. It travels the joists and the cable is stapled to them.

Photographs on this page are for illustration purposes only.

The actual mechanism

Why This Is a Real Fire Risk

The risk is not a cartoon short-circuit. It is this: gnawing removes insulation from a conductor, and a bare or nearly bare conductor sitting in loose-fill insulation and dry drey material is a heat source in a bed of fuel.

Two things make it worse than it sounds. Arcing at a damaged point generates far more local heat than the cable's normal load, and it can do so intermittently for a long time without tripping anything. And a circuit breaker protects against overload and short circuit — it is not designed to detect a small arc at a partially damaged cable, which can smoulder loft insulation without ever drawing enough current to operate.

An RCD improves the odds considerably where a fault goes to earth. It is not a guarantee, and it is not a reason to leave chewed cable in place.

What to look for

In the Loft, With a Torch

If you are going up to look, tread only on joists, keep off the insulation, and do not touch cable. What you are looking for:

• Bright copper anywhere. Exposed conductor is the thing that matters most and it stands out against grey sheathing.
• Missing sheath in short sections, often with neat parallel tooth marks at the edges.
• Cable pulled away from its clips or staples, sometimes into a drey.
• Sooting or scorch marks on timber or insulation near a cable. This is the one to act on immediately.
• A smell of hot plastic, with or without anything visible.

The wider set of signs — roofline evidence, loft evidence, and how to tell squirrel sign from rat and mouse sign — is covered in identifying the signs of squirrel damage.

Also worth checking: chewed plastic water pipe, and the lid of a cold water tank. A squirrel drowning in an open tank is a different problem and an unpleasant one.

Who to call

Two Trades, Not One

We deal with the animal, the way in and the clearing up. The cable is not a pest control job and we will not pretend otherwise.

Damaged wiring needs a competent electrician — someone registered with one of the recognised schemes, who can inspect and test the affected circuits and issue the appropriate certification for what they replace. Cable that has been gnawed gets replaced rather than taped, because tape restores neither the insulation rating nor the mechanical protection.

If you have scorching, or a smell of hot plastic, or lights and sockets behaving oddly, that is an electrician today rather than at your convenience. Turning off the affected circuit at the consumer unit in the meantime is reasonable, and safer than waiting with it live.

Insurance

Worth Asking Before You Spend

Some home policies cover damage caused by wild animals and some specifically exclude damage by rodents or vermin, and grey squirrels can fall on either side depending on the wording. It is worth reading yours rather than assuming, because the cost here is rarely the pest control — it is the rewiring and the insulation.

What helps a claim, whichever way the wording goes: photographs before anything is disturbed, a written record of what was found and where, dates, and the electrician's report on what needed replacing. We can provide our part of that as a matter of course. Ask for it at the time rather than afterwards.

We are not insurance advisers and we do not deal with insurers on anyone's behalf. What we can do is make sure you have the evidence in a form you can submit.

Short answers

Squirrel Questions

Going further

Squirrel Guides