Bulletproof walls are a vital part of any bulletproof system. Bullet-resistant acrylic windows, stainless-steel cash-trays, and UL-rated frames aren’t worth much if they’re bolted to a wall that can’t stop a shot from a .22 squirrel rifle.
What people commonly call “bulletproof walls” are really “bullet-resistant.” Such walls are made from materials that have been tested and rated by independent agencies who verify that the material can stop a specific number of shots from a specific caliber firearm. For example, a Level 4 bulletproof panel will stop a bullet from a .30-06 hunting rifle, while a Level 7 panel will stop five shots from an AR-15 style tactical rifle.
To these standards, some materials are natively “bulletproof”: a foot-thick concrete wall or two inches of solid steel will withstand many shots from a handgun, sub-machine gun, or rifle. But in most cases building contractors can’t do an entire job in poured concrete and heavy steel slabs; they need to rely on existing or easily constructed stud walls made from light wood or metal frames and sheets of drywall.
Bullet Resistant Fiberglass
For practical purposes, the key to building a bulletproof wall is bullet-resistant fiberglass (also called “opaque armor”). Fiberglass is a two-part laminated material made from a plastic polymer “matrix” reinforced with synthetic fibers. The material is lightweight, strong, and rigid once dried. During production—and prior to setting—fiberglass can be easily molded into any shape. (This makes it a popular material for boat hulls, auto body panels, and so on.)
The fiber at the heart of a bullet-resistant fiberglass panel is a super-tough synthetic mesh. At one time, this was usually DuPont™ Kevlar® fiber (the first such ultra-durable fiber available). Even though that specific brand of bullet-resistant fiber is rarely used in these panels today, it’s still the name most strongly associated with opaque bullet-resistant materials.
The Birth of Kevlar®
Developed in 1965 by DuPont™, Kevlar® was originally used to replace the steel and cloth belts in race car tires. The material itself is a woven synthetic para-aramid fiber (similar to nylon). DuPont had already invented several related aramid synthetic fibers, including Nomex® (which is still used to produce fire-resistant garments for firefighters and test pilots). Kevlar® shares Nomex’s® lack of a melting point and near-complete fire-resistance. But in contrast to Nomex® or nylon, when Kevlar® forms into fibers, its molecules naturally align themselves into long, unbroken chains along the fiber’s entire length. Subsequently, in addition to its fire-resistance, Kevlar® is also highly resistant to abrasion and shows incredible tensile strength—making it perfect for catching bullets.
Kevlar® Panels in Action
Bullet resistant fiberglass panels are made by saturating the synthetic fiber mesh with resin (which forms the “matrix” for the fiberglass). Flat layers of this resin-soaked mesh are then squeezed and baked by an industrial press. The result is a hard, dense, rigid panel. When it strikes one of these panels, a speeding bullet deforms, losing much of its momentum. The layers of resin-caked mesh separate, unfolding like an accordion—and absorbing even more of the bullet’s energy in the process. Then the practically unbreakable strands of Kevlar® enmeshed in the panel act like the walls of a batting cage, preventing the hard projectile (in this case, the bullet) from passing to the “protected” side of the barrier.
A bullet-resistant panel just 1/4-inch thick can stop at least three 9mm bullets fired dead on from just a few feet away. Need to stop a larger bullet? Just laminate together more layers of Kevlar® and resin during the production process, or layer up finished panels during installation.
Building Bullet Proof Walls
Contractors looking to build bulletproof walls start by framing a standard stud wall. They then mount bullet resistant fiberglass panels on the studs, making sure to double-over all seams with additional strips of fiberglass. Finally, the contractor covers the fiberglass wall with drywall or paneling. The resulting bulletproof wall can be finished just like any conventional wall: painted, wallpapered, decorated with framed landscapes or advertising. It’ll stop bullets as well as a bunker, but to any passers-by it’s indistinguishable from a standard wall.