Rats have strong teeth capable of chewing through many everyday materials, including wood, plastic, aluminum, and even some types of concrete. However, there are certain materials that rats simply cannot chew through because they are too hard or too dense. If you want to rat-proof your home or building, it is important to use these materials in critical areas such as around pipes, vents, foundation edges, and entry points.

The tooth force context: rat incisors can exert up to 7,000 psi of pressure — stronger than a human bite (150 psi) and enough to chew through lead pipes. The only reliable barrier materials are those harder than the rat's tooth enamel: steel, hardened concrete, ceramic, and glass.

Most Effective Rat-Proof Materials

• Steel: Rats cannot chew through steel. Steel is a hard metal that resists the pressure and sharpness of rat teeth. Common ways of using steel include installing steel mesh (with small holes no larger than 1/4 inch) or steel sheets to block access points. Use steel wool to pack gaps around pipes entering walls and foundations — cover with mortar or silicone.
• Stainless Steel: Like regular steel, stainless steel is tough and rust-resistant. Stainless steel wool is often used to stuff holes or fill gaps, and it works effectively because rats cannot chew through it or pull it out easily. Stainless steel mesh (1/4 inch): use over vents, weep holes, and larger openings.
• Thick Concrete: Rats are sometimes able to scrape or nibble at thin or crumbling concrete, but high-quality, thick concrete (at least 2 inches thick, properly mixed and cured) is impossible for them to chew through. Repair foundation cracks with hydraulic cement — not regular patching compound, which rats can crumble.
• Ceramics and Porcelain: These materials are used in tile and plumbing fixtures. Their hardness and brittle nature make them impossible for rats to chew through, though rats can still enter through joints or cracks if they exist.
• Glass: Smooth, dense glass is very hard for rats to grip or chew. Note that rats can break thin glass by knocking it over, but they cannot actually chew through it.
• Copper Mesh: While not as hard as steel, tightly-woven copper mesh (sometimes called "copper wool") is commonly used by professionals to fill small gaps. Rats dislike chewing on it and cannot break through when it's tightly packed and used correctly.

Less Reliable Materials That Might Fail

Some materials may seem tough, but rats can still get through them if given time or if the material is thin enough. These are commonly used in homes but should never be relied upon for rat-proofing:

• Plastic: Including PVC pipes, plastic sheeting, and bins – all of these can be chewed through easily.
• Soft Woods: Like pine or fir, these are no match for a rat's teeth.
• Aluminum: Thin sheets, flashing, and even some cans – rats can gnaw through these with effort.
• Spray Foams and Caulking: Useful for sealing air, but not for stopping rats. They'll chew straight through to get inside.
• Brick and Mortar: Very old or damaged brick and mortar can sometimes be worn away or scratched at, especially at joints.

Homeowners commonly use these materials and wonder why rats return: spray foam (can be chewed through in minutes), regular caulk (same), thin aluminum flashing (rats chew through within hours), chicken wire (large openings), and standard fiberglass window screen. None of these materials are effective against determined rats.

How to Use These Materials To Keep Rats Out

• To block holes or gaps, stuff them with tightly-packed stainless steel wool or copper mesh, then seal with mortar or pest-proof silicone.
• Cover vent openings with steel or stainless steel mesh (with small holes, 1/4 inch or less).
• Repair any concrete foundation cracks using high-quality concrete mix at least 2 inches thick.
• Replace wooden or plastic barriers with steel sheets or plates in areas where rats are likely to chew, like basement doors or shed floors.
• Inspect your property regularly for signs of gnawing or new holes – rats can create new entry points in weak materials quickly.

Why Rats Chew, and Why Only Some Materials Work

Rats must constantly chew because their front teeth (incisors) never stop growing. Chewing keeps their teeth from getting too long. Their teeth are extremely hard, even stronger than iron, but they still cannot bite through metals like steel or dense ceramics. Rats are determined, persistent, and able to squeeze through small spaces, so only the hardest materials — steel, stainless steel, copper mesh (when tightly packed), solid concrete, ceramics/glass — are fully effective barriers.

If you cover all possible entry points with these materials and stay vigilant for new weaknesses, you will successfully keep rats from chewing their way into your space.

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