Do pests chew through plastic or rubber materials?

The single most useful fact about rodent gnawing is that it has nothing to do with hunger. Rodent incisors are rootless and grow continuously — a house mouse's grow roughly 0.4 millimeters every day — and a rodent that stops wearing them down develops malocclusion and eventually starves. Gnawing is obligate maintenance.

That's why food storage isn't the whole answer, and why a spotless garage still gets chewed wiring. Recent work in Neuron (2026) went further and showed that gnawing is a dopamine-rewarded, motivated behavior rather than a passive mechanical response: disrupting the neural circuit abolished gnawing and produced severe malocclusion, while activating it triggered dopamine release. As the study's lead author put it, the old view was that gnawing was "a very passive behavior driven by mechanical considerations." It isn't. Your PEX line is a chew toy that happens to also be a chew toy they're rewarded for using.

Rodent incisor enamel sits around 5.5 on the Mohs scale, harder than iron, copper, platinum, and human enamel. The hardness comes from an iron-rich outer enamel layer; work published in ACS Nano (2024) found those iron-rich pockets make up less than two percent of the enamel by volume yet are decisive for its mechanical properties and acid resistance.

Against that, ordinary building plastics don't stand a chance: PEX and PVC supply lines, wire and cable insulation, foam board, expanding spray foam, vapor barriers, storage bins, weatherstripping, and soft metals like aluminum flashing and lead are all routinely breached. Flexible PVC and low-density polyethylene are chewed noticeably more than rigid PVC and high-density pipe — a distinction the exclusion literature has recognized for a long time.

Hardness is only half the mechanism. A rodent also needs an edge, seam, or rough spot to get its incisors around. A patent summarizing field and laboratory experience with rodent pipe damage describes the behavior plainly: the rodent first feels the pipe, and if it is hard like a rock, it moves away.

So the honest list of what rodents cannot chew is short, cheap, and boring: solid steel, cured concrete, glass, ceramic tile, and galvanized or stainless hardware cloth of an adequate gauge. That last one is not a coincidence — hardware cloth is the standard exclusion material precisely because decades of wildlife-damage-management practice found it holds. Standard extension guidance is to seal openings larger than about a quarter inch for mice and half an inch for rats, using materials from that list rather than foam or plastic.

This is why "they chew through anything" is worse than merely wrong. It's demoralizing, and it's the opposite of actionable. The real answer is that a rodent's list of victories is long but its list of defeats is specific, well known, and available at any hardware store.

It's worth being precise about what class of problem this is. Chewed plastic and rubber breaks systems — a supply line leaks, a wire faults, insulation stops insulating, a bin stops protecting what's in it. That's functional damage, and it's genuinely worth fixing.

What it isn't is structural. Rodents gnawing your PVC are not weakening your house. Framing, sheathing, and foundations are not on their menu, and no amount of chewed weatherstripping compounds into a compromised building. The pests that genuinely threaten structure are wood-destroying insects, and they're a different conversation entirely.

The one place this escalates in consequence rather than class is wiring, and it deserves care in both directions. Stripping the insulation off an energized conductor is a sound ignition pathway, and it's why chewed wire gets an electrician rather than a shrug. But you will also read that rodents cause 20 to 25 percent of house fires, and that figure appears in no fire-authority data — NFPA's research on home fires caused by electrical failure or malfunction identifies arcing as the leading factor and names no rodent factor at all. The mechanism is real; the number is invented. We give that its own honest treatment on the fire and wiring pages.