The answer to the question of whether a rat can chew through steel is no; they cannot penetrate solid, structural steel or hardened alloys. The common myth of rats gnawing through steel beams stems from their incredible ability to chew through nearly every other common building material. While a rat’s teeth and powerful jaw muscles give it a highly destructive capability against softer materials like wood, plastic, drywall, and thin metals, they are ultimately stopped by the high tensile strength of thick, quality steel. Understanding the biological drive and the unique composition of their teeth reveals the true limits of their destructive power.
The Biological Necessity of Chewing
The relentless chewing behavior observed in rats is not primarily an act of destruction but a biological necessity for survival. A rat’s four incisor teeth, two on the upper jaw and two on the lower, grow continuously throughout its entire life. If these teeth were not constantly worn down, they could grow by as much as one millimeter every day, leading to severe dental problems. This perpetual growth requires the rat to gnaw on hard, abrasive objects to prevent the teeth from overgrowing. The resulting condition, known as malocclusion, can cause the teeth to curve into the roof of the mouth or jaw, leading to painful injuries and an inability to eat. A rat that cannot chew will eventually starve, which is why the drive to gnaw is an instinctual compulsion.
Anatomy of the Rodent Incisor
The physical structure of the rat’s incisors makes them effective tools for gnawing. Unlike human teeth, a rat’s incisors are only coated with hard enamel on the front surface. The back surface of the tooth is made of much softer dentin. When the rat chews, the softer dentin wears away faster than the dense enamel, which constantly maintains a razor-sharp, chisel-like cutting edge. The incisor’s durability is enhanced by the presence of an iron-rich pigment within the enamel, which gives the teeth their distinctive yellow-orange color. This iron content significantly increases the hardness of the enamel, making it more resistant to wear and acid corrosion.
The Limits of Rat Bite Force
While the total biting force of a rat is modest, the pressure exerted at the point of the incisor is intense, which allows for significant penetration. The pressure exerted by a rat’s bite can reach up to 6,000 pounds per square inch (PSI) at the tip due to the concentration of force on a very small surface area. This high-pressure point determines the rat’s ability to breach a material. On the Mohs scale of hardness, rat teeth score approximately 5.5, which is harder than iron (4) and common steel (4 to 4.5). This hardness, combined with the extreme pressure, explains why rats can easily chew through soft metals like lead, thin aluminum sheeting, plastic pipes, and even concrete or mortar that is poorly cured. However, this power meets its match in structural or hardened steel, which possesses far greater tensile strength and hardness.
Effective Materials for Rodent Exclusion
To effectively prevent rats from gaining entry into a structure, materials must be used that exceed the limits of the rat’s dental capabilities. The most effective strategy involves using materials that are both too hard and too difficult for the rat to get a purchase on. Expanding foam and caulk are generally ineffective on their own because the rat can chew right through them.
The most successful exclusion materials include heavy-gauge hardware cloth, which is a sturdy wire mesh typically 16-gauge or thicker with small openings. Other highly recommended options are copper mesh, steel wool, or thick sheet metal flashing, which can be used to seal gaps around utility lines and foundation cracks. Using a non-corrosive material like steel wool or copper mesh and then backing it with concrete or a strong epoxy provides a permanent and impenetrable barrier.